JP5912874B2 - Humidity measurement system - Google Patents

Description

  The present invention provides a mirror-cooled dew point meter that measures the dew point temperature from dew condensation or frost generated on a mirror surface cooled using a thermoelectric cooling element in which one surface is a low temperature side and the other surface is a high temperature side. The present invention relates to a humidity measurement system using a humidity sensor that measures humidity based on a principle different from that of the mirror-cooled dew point meter.

  Conventionally, as a humidity measurement method, a dew point detection method is known in which a dew point is detected by measuring the temperature when the temperature of a gas to be measured is reduced and a part of water vapor contained in the gas to be measured is condensed. ing. For example, a mirror is cooled by using a cryogen, a refrigerator, an electronic cooler, etc., the change in the intensity of reflected light on the mirror surface of the cooled mirror is detected, and the mirror surface when the intensity of the reflected light is in an equilibrium state A mirror-cooled dew point meter that detects the dew point of moisture in the gas to be measured by measuring the temperature is used.

  There are two types of mirror-cooled dew point meters depending on the type of reflected light used. One is a specularly reflected light detection method that uses specularly reflected light (see, for example, Patent Document 1), and the other is a scattered light detection method that uses scattered light (see, for example, Patent Document 2).

[Specular reflection detection method]
FIG. 21 shows the configuration of a sensor unit in a conventional mirror-cooled dew point meter that employs a regular reflection light detection method. The sensor unit 101 includes a chamber 1 into which a gas to be measured flows and a thermoelectric cooling element (Peltier element) 2 provided at the bottom of the chamber 1. A mirror 3 is attached to the cooling surface 2-1 of the thermoelectric cooling element 2, and a heat radiating member 5 is attached to the heating surface 2-2 of the thermoelectric cooling element 2 via a heat pipe 4. That is, one end 4-1 of the heat pipe 4 is attached to the heating surface 2-2 of the thermoelectric cooling element 2, and the heat radiating member 5 is attached to the other end 4-2 of the heat pipe 4 separated from the thermoelectric cooling element 2. It has been.

  Further, a heat insulating member 6 is provided at one end 4-1 of the thermoelectric cooling element 2 and the heat pipe 4 so as to cover the periphery thereof, and a temperature detecting element 7 is attached to the upper surface (mirror surface) 3-1 of the mirror 3. It has been. In addition, a light emitting element 8 that irradiates light obliquely onto the mirror surface 3-1 of the mirror 3 and a regular reflection light of the light emitted from the light emitting element 8 to the mirror surface 3-1 are provided on the upper portion of the chamber 1. A light receiving element 9 for receiving light is provided. Further, a lead wire 10 to the thermoelectric cooling element 2 is provided through the heat insulating member 6.

  In the sensor unit 101, a gas to be measured flows into the chamber 1 through a branch pipe branched from a main pipe (not shown). Thereby, the mirror surface 3-1 in the chamber 1 is exposed to the gas to be measured. If condensation does not occur on the mirror surface 3-1, almost all of the light emitted from the light emitting element 8 is regularly reflected and received by the light receiving element 9. Therefore, when there is no condensation on the mirror surface 3-1, the intensity of the reflected light received by the light receiving element 9 is high.

  When the current to the thermoelectric cooling element 2 is increased and the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is lowered, water vapor contained in the measured gas is condensed on the mirror surface 3-1, and the water molecules Part of the light emitted from the light emitting element 8 is absorbed or irregularly reflected. Thereby, the intensity of the reflected light (regularly reflected light) received by the light receiving element 9 is reduced. By detecting the change in the specularly reflected light on the mirror surface 3-1, it is possible to know the change in the state on the mirror surface 3-1, that is, that moisture (water droplets) has adhered to the mirror surface 3-1. Further, by measuring the temperature of the mirror surface 3-1 at this time with the temperature detecting element 7, the dew point of the moisture in the gas to be measured can be known. Then, the humidity of the gas to be measured can be obtained by converting the temperature of the dew point using a calculation formula or the like.

(Scattered light detection method)
FIG. 22 shows a configuration of a sensor unit in a conventional mirror-cooled dew point meter that employs a scattered light detection method. The sensor unit 102 has substantially the same configuration as the sensor unit 101 adopting the regular reflection light detection method, but the mounting position of the light receiving element 9 is different. In the sensor unit 102, the light receiving element 9 is provided at a position for receiving scattered light, not at a position for receiving regular reflection light of light emitted from the light emitting element 8 to the mirror surface 3-1.

  In the sensor unit 102, a gas to be measured flows into the chamber 1 via a branch pipe branched from a main pipe (not shown). Thereby, the mirror surface 3-1 in the chamber 1 is exposed to the gas to be measured. If there is no condensation on the mirror surface 3-1, almost all of the light emitted from the light emitting element 8 is regularly reflected, and the amount of light received by the light receiving element 9 is extremely small. Therefore, when no condensation occurs on the mirror surface 3-1, the intensity of the reflected light received by the light receiving element 9 is small.

  When the current to the thermoelectric cooling element 2 is increased and the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is lowered, water vapor contained in the measured gas is condensed on the mirror surface 3-1, and the water molecules Part of the light emitted from the light emitting element 8 is absorbed or irregularly reflected. Thereby, the intensity | strength of the irregularly reflected light (scattered light) received by the light receiving element 9 increases. By detecting the change in the scattered light on the mirror surface 3-1, it is possible to know the change in the state on the mirror surface 3-1, that is, that moisture (water droplets) has adhered to the mirror surface 3-1. Further, by measuring the temperature of the mirror surface 3-1 at this time with the temperature detecting element 7, the dew point of the moisture in the gas to be measured can be known. Then, the humidity of the gas to be measured can be obtained by converting the temperature of the dew point using a calculation formula or the like.

  In addition, in the dew point meter mentioned above, although demonstrated in the example which detects the dew condensation (dew point) which arises on the mirror surface 3-1, it is also possible to detect the dew condensation (frost point) which arises on the mirror surface 3-1 by the same structure. It is. In this specification, the temperature including the frost point is defined as the dew point temperature.

  In such a mirror-cooled dew point meter, a substance (for example, an organic solvent) that condenses at a low temperature may be mixed in the gas to be measured. That is, there is a case where a substance that is usually a gas and is contained in the gas to be measured and becomes a solid at a low temperature higher than the dew point temperature may be included. If such a substance condenses and adheres to the mirror surface as it cools down to measure the dew point temperature, the condensed material adhering to the mirror surface adversely affects the reflected or scattered light, and the dew point temperature is accurately measured. (Humidity measurement) cannot be performed. For example, if condensate adheres during continuous dew point measurement and the mirror surface becomes dirty, the measurement becomes unstable, or the detection of dew condensation becomes abnormal due to contamination, and it is determined that dew condensation is excessive and the dew point temperature rises. Sometimes.

  Therefore, conventionally, in order to prevent contamination of the mirror surface, the dew point temperature measurement is periodically interrupted and the mirror surface is manually cleaned with a cotton swab or the like, as shown in Patent Document 3, The condensate contained in is removed by a removing device before being guided to the mirror surface, or as disclosed in Patent Document 4, CO2 gas is blown to blow away the condensate from the mirror surface.

JP-A-61-75235 Japanese Patent Publication No. 07-104304 JP 2002-189007 A JP 05-99846 A

  However, in the method of manually cleaning the mirror surface, the dew point temperature measurement must be periodically interrupted, and a mirror surface contamination alarm may occur frequently when checking the surface of the mirror surface. Further, the cleaning work is troublesome, and the dew point temperature measurement must be interrupted for a relatively long time for the cleaning work, and the dew point temperature cannot be continuously measured (humidity continuous measurement).

  Further, in the method of removing the condensed substance before the measurement gas is guided to the mirror surface, the condensed substance is specified in advance, and a removing device for removing it by a chemical reaction or the like is required. Also, it is not adapted for all condensed matter.

  In the method in which the condensed material is blown off from the mirror surface by blowing CO2 gas, a device for blowing CO2 gas is required, and measurement of the dew point temperature must be interrupted while CO2 gas is being blown.

  The present invention has been made in order to solve such problems. The object of the present invention is usually to perform highly accurate humidity measurement with a mirror-cooled dew point meter while the mirror surface of the mirror-cooled dew point meter. If the measurement accuracy drops due to contamination, etc., humidity measurement is performed without interruption by using a humidity sensor that measures humidity according to a principle different from that of a mirror-cooled dew point meter. It is an object to provide a humidity measurement system capable of performing the above.

  In addition, when humidity measurement is performed by a humidity sensor, the mirror surface is manually cleaned by performing automatic cleaning control to remove condensed substances that may have adhered to the mirror surface of the mirror-cooled dew point meter. It is an object of the present invention to provide a humidity measurement system that can be dispensed with and eliminates the need for a separate apparatus for removing condensed substances.

In order to achieve such an object, the present invention irradiates light to a mirror surface exposed to a gas to be measured, a thermoelectric cooling element that cools the mirror surface, a temperature sensor that detects the temperature of the mirror surface, and the mirror surface. A light projecting means, a light receiving means for receiving reflected light of the light emitted from the light projecting means to the mirror surface, and a control for controlling the current supplied to the thermoelectric cooling element based on the amount of reflected light received by the light receiving means. And the control means controls the current supplied to the thermoelectric cooling element based on the amount of reflected light received by the light receiving means so that there is no increase or decrease in condensation or frost on the mirror surface, Specular cooling dew point meter equipped with means to execute dew point temperature measurement control that measures temperature of mirror surface detected by temperature sensor in equilibrium state as dew point temperature The A humidity sensor to measure, a humidity measurement value obtained by converting a dew point temperature measured by a mirror-cooled dew point meter as a first humidity measurement value, and a humidity measurement value measured by the humidity sensor as a second A humidity measurement system for selecting a humidity measurement value and selecting one of the first and second humidity measurement values as an effective humidity measurement value and outputting the selected humidity as a formal humidity measurement value of a gas to be measured. and reliability determining means for determining the reliability of the humidity measurement values, if the reliability of the first humidity measurement by the reliability judging means is affirmative, selects the first humidity measurement as valid humidity measurements while the formal humidity measurements during normal Te, when the reliability of the first humidity measurement by the reliability judging means is negative, the abnormality by selecting a second humidity measurement as valid humidity measurements humidity and formal humidity measurement value of time Characterized in that it comprises a measurement value selecting means.

In this invention, the humidity measurement value obtained by converting the dew point temperature measured by the specular cooling dew point meter is the first humidity measurement value, and the humidity measurement value measured by the humidity sensor (mirror surface cooling dew point meter and Is the second humidity measurement value, one of the first and second humidity measurement values is selected as the effective humidity measurement value, and the measured gas Is output as an accurate humidity measurement. In outputting the official humidity measurement value of the gas to be measured, the present invention determines the reliability of the first humidity measurement value, and if the reliability of the first humidity measurement value is affirmed, the first When the humidity measurement value of 1 is selected as an effective humidity measurement value and becomes the official humidity measurement value during normal times, and the reliability of the first humidity measurement value is denied, the second humidity measurement value is used as an effective humidity measurement value. Select the value as the official humidity measurement at the time of abnormality . As a result, high-precision humidity measurement is usually performed with a mirror-cooled dew point meter, and when the measurement accuracy is reduced due to contamination of the mirror surface of the mirror-cooled dew point meter, what is a mirror-cooled dew point meter? Humidity measurement is performed by a humidity sensor that measures humidity according to a different principle, and humidity measurement is continuously performed without interruption.

  In the present invention, the reliability of the first humidity measurement value is determined. For example, as the first method, the dew point temperature measurement control of the mirror-cooled dew point meter is periodically interrupted, and the light receiving means receives the light. It is conceivable to determine the reliability of the first humidity measurement value based on the amount of reflected light. As a second method, it is conceivable to determine the reliability of the first humidity measurement value based on the difference between the first humidity measurement value and the second humidity measurement value.

  In the present invention, when the above-described first method is adopted, it is necessary to periodically interrupt the dew point temperature measurement control of the mirror-cooled dew point meter in order to determine the reliability of the first humidity measurement value. On the other hand, if the above-mentioned second method is adopted, humidity measurement can be performed without interruption even during dew point temperature measurement control, not only when the mirror surface of the mirror-cooled dew point meter gets dirty and the measurement accuracy drops. Can be performed continuously.

  Further, in the present invention, when humidity measurement is performed by a humidity sensor, if automatic cleaning control for removing condensed substances that may adhere to the mirror surface of the mirror-cooled dew point meter is executed, Therefore, it is possible to eliminate the need to separately provide a device for removing condensed substances. In this case, as an automatic cleaning control, a method of controlling the current supplied to the thermoelectric cooling element so as to raise the temperature of the mirror surface in order to remove condensed substances that would have adhered to the mirror surface, is attached to the mirror surface. In order to remove the condensate that would have been, it is conceivable to adopt a system in which the pressure in the chamber containing the mirror surface, thermoelectric cooling element, temperature sensor, light projecting means and light receiving means is controlled to be reduced.

According to the present invention, the humidity measurement value obtained by converting the dew point temperature measured by the specular cooling type dew point meter is the first humidity measurement value, and the humidity is measured based on a principle different from the specular cooling type dew point meter. When the humidity measurement value measured by the sensor is used as the second humidity measurement value, the reliability of the first humidity measurement value is determined, and the reliability of the first humidity measurement value is affirmed, the first humidity measurement Select the value as a valid humidity measurement value to make it the normal official humidity measurement value, and if the reliability of the first humidity measurement value is denied, select the second humidity measurement value as the effective humidity measurement value Therefore, the humidity measurement value is set to the official humidity measurement value at the time of abnormality , so usually the mirror-cooled dew point meter performs high-precision humidity measurement, while the mirror surface of the mirror-cooled dew point meter becomes dirty and the measurement accuracy is improved. If it falls off, it is different from the mirror-cooled dew point meter. In so as to perform humidity measured by the humidity sensor for measuring the humidity, it is possible to perform continuously the humidity measured without interruption.
In addition, according to the present invention, when humidity measurement is performed by a humidity sensor, automatic cleaning control for removing condensed substances that may have adhered to the mirror surface of the mirror-cooled dew point meter is performed, It is not necessary to manually clean the mirror surface, and it is possible to eliminate the need to provide a separate device for removing condensed substances.

It is a schematic block diagram of the mirror surface cooling-type dew point meter used for the humidity measurement system which concerns on this invention. It is a figure which shows the installation condition of the gate valve and suction pump for guide | inducing a to-be-measured gas in the sampling chamber of this specular cooling type dew point meter. It is a flowchart which shows the operation | movement by the side of the sub controller in this mirror surface cooling type dew point meter. It is a figure which shows the pulsed light irradiated with respect to the mirror surface in this mirror surface cooling-type dew point meter, and the reflected pulsed light received from a mirror surface. It is a figure which shows the cooling curve (characteristics I and II) of a subcooler and a 1st thermoelectric cooling element in this mirror surface cooling-type dew point meter. It is a flowchart which shows normal / abnormal determination of the mirror surface state performed in this mirror surface cooling type dew point meter, and the shift operation to automatic cleaning. It is a flowchart which shows operation | movement at the time of confirming that the change of mirror surface temperature no longer arises in this mirror surface cooling-type dew point meter confirming normality / abnormality of a mirror surface state. It is a flowchart which shows operation | movement at the time of confirming that the change of reflected light amount no longer arises in this mirror surface cooling-type dew point meter, and judging whether the mirror surface state is normal / abnormal. It is a flowchart which shows another example of the determination operation | movement of the normal / abnormality of a mirror surface state performed regularly in this mirror surface cooling-type dew point meter, and the transfer operation | movement to automatic cleaning. FIG. 11 is a flowchart showing another example of the operation in the case of determining whether the specular state is normal or abnormal in the specular cooling type dew point meter after confirming that the change in specular temperature no longer occurs. It is a flowchart which shows the operation | movement of another example at the time of confirming that the change of reflected light quantity no longer arises in this specular cooling type dew point meter, and confirming whether the specular state is normal / abnormal. It is a functional block diagram of the principal part of this mirror surface cooling type dew point meter. It is a time chart which shows the change of the control mode in this mirror surface cooling type dew point meter. It is a functional block diagram of the principal part of 1st Embodiment (Embodiment 1) of the humidity measurement system which concerns on this invention. It is a time chart which shows the change of the control mode in the specular cooling type dew point meter in operation of the humidity measurement system of Embodiment 1, and the measurement state of a humidity sensor. 3 is a control flowchart of the mirror-cooled dew point meter in the humidity measurement system according to the first embodiment. 4 is a control flowchart of the overall controller in the humidity measurement system according to the first embodiment. It is a functional block diagram of the principal part of 2nd Embodiment (Embodiment 2) of the humidity measurement system which concerns on this invention. It is a time chart which shows the change of the control mode in the specular cooling dew point meter in operation of the humidity measurement system of Embodiment 2, and the measurement state of a humidity sensor. It is a figure which shows the structural example at the time of installing a mirror surface cooling-type dew point meter and a humidity sensor in series. It is a figure which shows the structure of the sensor part in the conventional mirror surface cooling-type dew point meter which employ | adopted the regular reflection light detection system. It is a figure which shows the structure of the sensor part in the conventional mirror surface cooling-type dew point meter which employ | adopted the scattered light detection system.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, before entering into the description of the embodiment of the humidity measurement system according to the present invention, a specular cooling dew point meter used in this humidity measurement system will be described.

[Mirror surface dew point meter]
FIG. 1 is a schematic configuration diagram of a single unit of this mirror-cooled dew point meter. The mirror-cooled dew point meter 201 has a sensor unit 201A and a control unit 201B.

(Sensor part)
In the sensor unit 201A, reference numeral 11 denotes a mirror, and the surface 11-1 is a mirror surface. The mirror 11 is, for example, a silicon chip, and the cooling surface 2-1 of the first thermoelectric cooling element (Peltier element) 2 is attached to the back surface 11-2 side of the mirror 11. In addition, a first temperature sensor 12 made of platinum, for example, is provided between the mirror 11 and the cooling surface 2-1 of the first thermoelectric cooling element 2. The first temperature sensor 12 detects the temperature of the back surface 11-2 of the mirror 11 as the mirror surface temperature tPpv.

  The first thermoelectric cooling element 2 is attached to the inclined surface 13b of the tip end portion 13a of the sensor body 13 with the heating surface 2-2 as the bottom surface. The inclined surface 13 b has an inclination angle of 30 ° to 45 ° with respect to the central axis of the sensor body 13. Therefore, the mirror surface 11-1 of the mirror 11 attached to the cooling surface 2-1 of the first thermoelectric cooling element 2 with the first temperature sensor 12 interposed therebetween is also 30 ° to 45 ° with respect to the central axis of the sensor body 13. Is tilted at an angle of

  A rear end portion 13c connected to the front end portion 13a of the sensor body 13 has a cylindrical shape. The rear end portion 13c holds a light projecting / receiving integrated optical fiber 14 with its front end face facing the mirror surface 11-1. The light projecting axis and the light receiving axis of the light projecting / receiving integrated optical fiber 14 are parallel to the central axis of the sensor body 13. In this example, among the optical fibers 14-1 and 14-2 of the light projecting / receiving integrated optical fiber 14 protruding from the rear end portion 13c toward the mirror surface 11-1, 14-1 is disposed on the light projecting side. The optical fiber 14-2 is an optical fiber on the light receiving side.

  A cooling block 15 is joined to the rear portion of the rear end portion 13 c of the sensor body 13. A cooling plate 16 is joined to the rear part of the cooling block 15. The sensor body 13, the cooling block 15, and the cooling plate 16 are all heat conductive members, and the sensor body 13, the cooling block 15, and the cooling plate 16 constitute a heat conductor 17.

  A second thermoelectric cooling element (Peltier element) 18 is provided at the rear of the cooling plate 15. The second thermoelectric cooling element 18 is attached to the heat conductor 17 with the cooling surface 18-1 as the cooling plate 16 side. That is, the heating surface 2-2 of the first thermoelectric cooling element 2 is attached to one end of the heat conductor 17, and the cooling surface 18-1 of the second thermoelectric cooling element 18 is attached to the other end of the heat conductor 17. ing. In this specular cooling type dew point meter 201, the cooling capacity of the second thermoelectric cooling element 18 is much larger than the cooling capacity of the first thermoelectric cooling element 2, as can be seen by comparing the sizes thereof. Has been.

  A heat sink 19 is joined to the heating surface 18-2 of the second thermoelectric cooling element 18 as a radiator. The heat sink 19 has a large number of radiating fins 19a. The heat sink 19 is also a heat conductive member like the heat conductor 17. A cooling fan 20 is provided behind the heat sink 19, and a second temperature sensor 21 is provided on the cooling plate 16. The second temperature sensor 21 detects the temperature of the cooling surface 18-1 of the second thermoelectric cooling element 18 as the subcooler temperature tSpv.

  In this mirror-cooled dew point meter 201, a configuration in which the cooling plate 16, the second thermoelectric cooling element 18, the heat sink 19 and the cooling fan 20 are combined is called an auxiliary cooler (subcooler). The main configuration is the second thermoelectric cooling element 18, and the second thermoelectric cooling element 18 alone may be called an auxiliary cooler (subcooler). Here, a configuration in which the cooling plate 16, the second thermoelectric cooling element 18, the heat sink 19, and the cooling fan 20 are combined is referred to as a subcooler SC.

  Further, the mirror-cooled dew point meter 201 includes the first thermoelectric cooling element 2, the mirror 11, the first temperature sensor 12, the light-emitting side optical fiber 14-1, the light-receiving side optical fiber 14-2, and the like. The detector DT is provided through the heat insulating material 32 in the sampling chamber 31 into which the gas to be measured is drawn. Further, as shown in FIG. 2, the sampling chamber 31 is provided with a gate valve 40 and a suction pump 41 for guiding the gas to be measured to the sampling chamber 31.

  Further, the photoelectric converter 22 is provided in the sensor unit 201A. The photoelectric converter 22 converts the electrical signal from the control unit 201B into an optical signal and supplies it to the light-projecting optical fiber 14-1, or converts the optical signal from the light-receiving optical fiber 14-2 into an electrical signal. To the control unit 201B. The connection relationship between the photoelectric converter 22 and the control unit 201B will be described later. The sensor unit 201A is provided with an outside air temperature sensor 23 that detects the temperature of outside air sucked by the cooling fan 20 as tout. The outside air temperature tout detected by the outside air temperature sensor 23 is sent to the control unit 201B.

[Control part]
The control unit 201B includes a main controller 24, a sub controller 25, a power source 26, a power switch 27, a dew point measurement ON / OFF switch 28, a sub cooler control ON / OFF switch 29, and a sub cooler low temperature / high temperature / interlocking switch. A selector switch 30 is provided.

  The main controller 24 includes a CPU 24-1, a first A / D converter 24-2, a second A / D converter 24-3, a dew point temperature output unit 24-4, a RAM 24-5, ROM 24-6. The CPU 24-1 operates according to a program stored in the ROM 24-6 while obtaining various input information from the outside and accessing the RAM 24-5. The ROM 24-6 stores a dew point measurement program.

  In the main controller 24, the first A / D converter 24-2 digitally converts the optical signal (signal S4) from the light receiving side optical fiber 14-2 converted into the electrical signal from the photoelectric converter 22. It converts into a signal and gives to CPU24-1. Further, the second A / D converter 24-3 converts the mirror surface temperature tPpv (signal S2) from the first temperature sensor 12 into a digital signal and supplies the digital signal to the dew point temperature output unit 24-4 and the CPU 24-1. . The dew point temperature output unit 24-4 sends the mirror surface temperature tPpv converted into the digital signal from the first temperature sensor 12 to the host device as the dew point temperature.

  The sub-controller 25 includes a CPU 25-1, a first A / D converter 25-2, a second A / D converter 25-3, a RAM 25-4, and a ROM 25-5. The CPU 25-1 obtains various input information from the outside, and operates according to the program stored in the ROM 25-5 while accessing the RAM 25-4. The ROM 25-5 stores a subcooler control program.

  In the sub-controller 25, the first A / D converter 25-2 converts the sub-cooler temperature tSpv (signal S6) from the second temperature sensor 21 into a digital signal and supplies it to the CPU 25-1. Further, the second A / D converter 25-3 converts the outside air temperature tout (signal S8) from the outside air temperature sensor 23 into a digital signal and gives it to the CPU 25-1. Further, the mirror temperature tPpv from the first temperature sensor 12 is given to the CPU 25-1 via the second A / D converter 24-3 in the main controller 24. Further, as shown in FIG. 2, the CPU 25-1 of the sub-controller 25 controls the opening / closing of the gate valve 40 and the operation / stop of the suction pump 41 in response to a command from the CPU 24-1 of the main controller 24.

[Sub-cooler low temperature / high temperature / linked switching setting]
In this mirror-cooled dew point meter 201, whether the subcooler SC is operated at “low temperature (for example, fixed at −5 ° C.)” or “high temperature (for example, fixed at 25 ° C.)” It is possible to selectively set the operation mode using the subcooler low temperature / high temperature / interlocking selector switch 30 as to whether to operate at “temperature + α)”.

[Dew point measurement with the operation mode set to "low temperature"]
Now, the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “low temperature”, and dew point measurement is started. In this case, it is assumed that the power switch 27 has already been turned on and the main controller 24 and the sub-controller 25 are in a state of being supplied with power.

  When dew point measurement is started, both the dew point measurement ON / OFF switch 28 and the subcooler control ON / OFF switch 29 are turned ON. The subcooler control ON / OFF switch 29 may be turned on first, and the dew point measurement ON / OFF switch 28 may be turned on after a certain period of time. It is assumed that the subcooler control ON / OFF switch 29 is turned ON simultaneously.

  When the sub-cooler control ON / OFF switch 29 is turned on, the CPU 24-1 of the main controller 24 sets the sub-cooler control ON / OFF switch 29 in accordance with the current setting state of the sub-cooler low temperature / high temperature / interlocking selector switch 30. The CPU 25-1 of the sub-controller 25 is informed that it has been turned ON.

[Operation on the sub-controller side]
When the CPU 25-1 of the sub-controller 25 receives notification from the main controller 24 that the sub-cooler control ON / OFF switch 29 has been turned ON (FIG. 3: YES in step S101), it opens the gate valve 40 (step S102). Then, the operation of the suction pump 41 is started (step S103), the inflow of the gas to be measured into the sampling chamber 31 is started, and the operation of the cooling fan 20 is started (step S104, signal S5). It should be noted that when the power switch 27 is turned on, the introduction of the gas to be measured into the sampling chamber 31 (opening of the gate valve 40 and the operation of the suction pump 41) and the operation of the cooling fan 20 may be started. Good.

  Further, the CPU 25-1 of the sub controller 25 checks the current setting state of the sub cooler low temperature / high temperature / interlocking switch selector switch 30 notified from the main controller 24 (step S105). In this case, since the setting state of the subcooler low temperature / high temperature / interlocking selector switch 30 is “low temperature”, the process proceeds to step S109 through step S108, and the set target temperature Tsp of the subcooler is set to a low temperature (for example, −5 ° C.). And

  Then, the subcooler temperature tSpv from the second temperature sensor 21 is taken in (step S114, signal S6), and the current supplied to the second thermoelectric cooling element 18 is set so that the subcooler temperature tSpv and the set target temperature Tsp match. ON / OFF control is performed (step S115, signal S7).

[Operation on the main controller side]
On the other hand, when the dew point measurement ON / OFF switch 28 is turned on, the CPU 24-1 of the main controller 24 sends a signal S3 to the photoelectric converter 22, and the mirror surface from the front end surface of the optical fiber 14-1 on the light projecting side. 11-1 is irradiated with light at a predetermined cycle (see FIG. 4A). Note that the photoelectric converter 22 may be configured to irradiate light from the distal end surface of the light-projecting optical fiber 14-1 when the power switch 27 is turned on.

  If the mirror surface 11-1 is exposed to the gas to be measured and no condensation occurs on the mirror surface 11-1, almost all of the light emitted from the tip of the optical fiber 14-1 on the light projecting side is specularly reflected. However, the amount of reflected light (scattered light) from the mirror surface 11-1 received through the optical fiber 14-2 on the light receiving side is extremely small. Therefore, when no condensation occurs on the mirror surface 11-1, the intensity of the reflected light received through the light receiving side optical fiber 14-2 is small. The reflected light received through the optical fiber 14-2 on the light receiving side is converted into an electric signal by the photoelectric converter 22 and sent to the first A / D converter 24-2 of the main controller 24, where it is a digital signal. Is converted into and taken into the CPU 24-1.

  The CPU 24-1 obtains the difference between the upper limit value and the lower limit value of the reflected light received through the light receiving side optical fiber 14-2 as the intensity of the reflected light. In this case, since the intensity of the reflected light is almost zero and has not reached a predetermined threshold value (setting value for dew condensation determination), the CPU 24-1 generates a current to the first thermoelectric cooling element 2. Increase (signal S1). Thereby, the temperature of the cooling surface 2-1 of the first thermoelectric cooling element 2 is lowered.

  When the temperature of the cooling surface 2-1 of the first thermoelectric cooling element 2 is lowered, that is, the temperature of the mirror surface 11-1, the water vapor contained in the gas to be measured is condensed on the mirror surface 11-1, and the water molecules Part of the light emitted from the tip of the optical fiber 14-1 on the light projecting side is absorbed or irregularly reflected. Thereby, the intensity | strength of the reflected light (scattered light) from the mirror surface 11-1 light-received via the optical fiber 14-2 by the light-receiving side increases.

  Here, when the intensity of the reflected light received through the optical fiber 14-2 on the light receiving side exceeds the threshold value, the CPU 24-1 reduces the current to the first thermoelectric cooling element 2. Thereby, the fall of the temperature of the cooling surface 2-1 of the 1st thermoelectric cooling element 2 is suppressed, and generation | occurrence | production of dew condensation is suppressed. By suppressing this dew condensation, the intensity of the reflected light received through the optical fiber 14-2 on the light receiving side becomes small, and when it falls below the threshold, the CPU 24-1 increases the current to the first thermoelectric cooling element 2. Let

  By repeating this operation, the temperature of the cooling surface 2-1 of the first thermoelectric cooling element 2 is adjusted so that the intensity of the reflected light received through the optical fiber 14-2 on the light receiving side is approximately equal to the threshold value. Adjusted. The adjusted temperature, that is, the temperature at which the dew condensation occurring on the mirror surface 11-1 reaches the equilibrium state (dew point temperature) is sent to the dew point temperature output unit 24-4.

  In this dew point detection operation, the heating surface 2-2 of the first thermoelectric cooling element 2 is cooled by the subcooler SC including the second thermoelectric cooling element 18 via the heat conductor 17. FIG. 5 shows a cooling curve of the subcooler SC as a characteristic I, and shows a cooling curve of the first thermoelectric cooling element 2 as a characteristic II. For reference, a cooling curve is shown as characteristic III when the subcooler SC is not used and the thermoelectric cooling element for mirror surface cooling is a large multistage Peltier.

  As can be seen by comparing the characteristic II and the characteristic III, when the thermoelectric cooling element for mirror surface cooling is a large multi-stage Peltier, the heat capacity around the mirror surface increases, and the responsiveness deteriorates. On the other hand, when the subcooler SC is used, the heat capacity around the mirror surface can be kept small, so that the responsiveness does not deteriorate.

  In this way, in this mirror-cooled dew point meter 201, by using the subcooler SC, it is possible to use a small element (Peltier with a high cooling speed) having a relatively small cooling capacity as the first thermoelectric cooling element 2. ing. For this reason, responsiveness is not sacrificed, and enlargement of the size around the mirror surface can be avoided. In addition, since a Peltier-type cooler is used for the subcooler SC, a refrigerant-type cooler and piping are not required, the apparatus is not complicated, and the size is reduced. Moreover, there is no fear of refrigerant leakage.

[Dew point measurement with the operation mode set to "Linked"]
Next, a case where the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “interlocking” and dew point measurement is started will be described. Also in this case, the dew point measurement ON / OFF switch 28 and the subcooler control ON / OFF switch 29 are simultaneously turned ON.

  When the sub-cooler control ON / OFF switch 29 is turned on, the CPU 24-1 of the main controller 24 sets the sub-cooler control ON / OFF switch 29 in accordance with the current setting state of the sub-cooler low temperature / high temperature / interlocking selector switch 30. The CPU 25-1 of the sub-controller 25 is informed that it has been turned ON.

[Operation on the sub-controller side]
When the CPU 25-1 of the sub-controller 25 receives notification from the main controller 24 that the sub-cooler control ON / OFF switch 29 has been turned ON (FIG. 3: YES in step S101), it opens the gate valve 40 (step S102). Then, the operation of the suction pump 41 is started (step S103), the inflow of the gas to be measured into the sampling chamber 31 is started, and the operation of the cooling fan 20 is started (step S104, signal S5).

  Further, the CPU 25-1 of the sub controller 25 checks the current setting state of the sub cooler low temperature / high temperature / interlocking switch selector switch 30 notified from the main controller 24 (step S105). In this case, since the setting state of the subcooler low temperature / high temperature / interlocking selector switch 30 is “interlocking”, the mirror surface temperature tPpv from the first temperature sensor 12 is acquired (step S106), and the set target temperature of the subcooler is acquired. Tsp is set to a mirror surface temperature tPpv + α (step S107).

  Then, the outside air temperature tout from the outside air temperature sensor 23 is taken in (step S111), and the set target temperature Tsp determined in step S107 is compared with the outside air temperature tout (step S112). If the set target temperature Tsp is equal to or lower than the outside air temperature tout (YES in step S112), the sub-cooler temperature tSpv from the second temperature sensor 21 is taken in (step S114), and the sub-cooler temperature tSpv and the set target temperature Tsp are The current supplied to the second thermoelectric cooling element 18 is ON / OFF controlled so as to match (step S115).

  On the other hand, when the set target temperature Tsp is higher than the outside air temperature tout (NO in step S112), the set target temperature Tsp is set to the outside air temperature tout (step S113), that is, the upper limit value of the set target temperature Tsp is set to the outside air temperature. The current supplied to the second thermoelectric cooling element 18 is controlled to be ON / OFF so that the subcooler temperature tSpv and the set target temperature Tsp coincide with each other (steps S114 and S115).

[Operation on the main controller side]
The operation on the main controller 24 side is the same as the case where the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “low temperature”, and the description thereof is omitted here.

  When the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “low temperature”, that is, when the set target temperature Tsp of the subcooler is fixed at a low temperature (for example, −5 ° C.), the fixed set target temperature A dew point higher than Tsp cannot be measured. Even when the dew point near the upper limit of the measurement range is measured, a large amount of energy is consumed because the set target temperature Tsp is fixed.

  On the other hand, if the subcooler low temperature / high temperature / linkage selector switch 30 is set to “linkage”, that is, if the set target temperature Tsp of the subcooler is set to the mirror surface temperature tPpv + α, the set target temperature Tsp increases as the mirror surface temperature tPpv increases. Therefore, the dew point can be measured up to the same temperature as the ambient temperature. Further, since the set target temperature Tsp always fluctuates at the mirror surface temperature tPpv + α, the consumed energy becomes the minimum necessary.

[Mirror surface maintenance (1)]
For example, it is assumed that maintenance of the mirror surface 11-1 is desired during dew point measurement with the operation mode set to "low temperature". In this case, the dew point measurement ON / OFF switch 28 is turned OFF, and the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “high temperature”.

  Then, the CPU 24-1 of the main controller 24 interrupts the cooling operation of the mirror surface 11-1 by the first thermoelectric cooling element 2, and the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “high temperature”. Is notified to the CPU 25-1 of the sub-controller 25.

  When the CPU 25-1 of the sub-controller 25 receives notification from the main controller 24 that the sub-cooler low temperature / high temperature / interlocking selector switch 30 has been set to “high temperature”, the sub-cooler set target temperature Tsp is set to a high temperature (for example, 25 ° C) (FIG. 3: Steps S108 and S110).

  Then, the subcooler temperature tSpv from the second temperature sensor 21 is taken in (step S114), and the current supplied to the second thermoelectric cooling element 18 is turned ON / OFF so that the subcooler temperature tSpv and the set target temperature Tsp match. Control is performed (step S115). In this case, since the set target temperature Tsp is higher than the subcooler temperature tSpv, a reverse current is applied to the second thermoelectric cooling element 18. Thereby, subcooler SC is utilized as a heater and the mirror surface is returned to room temperature in a short time.

[Mirror surface maintenance (2)]
For example, it is assumed that maintenance of the mirror surface 11-1 is to be performed during the dew point measurement with the operation mode “interlocking”. In this case, the dew point measurement ON / OFF switch 28 is turned OFF and the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “high temperature” in the same manner as during dew point measurement with the operation mode set to “low temperature”. However, the dew point measurement ON / OFF switch 28 may be simply turned OFF.

  When the dew point measurement ON / OFF switch 28 is turned OFF, the CPU 24-1 of the main controller 24 interrupts the cooling operation of the mirror surface 11-1 by the first thermoelectric cooling element 2. In this case, the CPU 25-1 of the sub-controller 25 continues control to set the sub-cooler target temperature Tsp to the mirror surface temperature tPpv + α. Thereby, the set target temperature Tsp of the subcooler also increases as the temperature increases due to the interruption of the cooling operation of the mirror surface 11-1.

  In this way, if dew point measurement is being performed with the operation mode set to “interlocking”, the decool point measurement ON / OFF switch 28 is simply turned OFF, and the set target temperature Tsp of the subcooler is automatically switched without switching to a high temperature. The mirror surface can be returned to room temperature.

[Performance of main controller and sub controller]
In this mirror-cooled dew point meter 201, the generation speed of condensation on the mirror surface 11-1 is very fast, and the mirror surface temperature tPpv and the amount of reflected light from the mirror surface must be measured with high accuracy. On the other hand, the control of the subcooler SC is slow because the heat capacity is large, and the detection of the subcooler temperature tSpv does not require much accuracy.

  Therefore, in the mirror-cooled dew point meter 201, the main controller 24 requires high-speed control and high-accuracy measurement. Therefore, a high-performance and high-price controller is used, and the sub-controller 25 requires less control performance and measurement accuracy. Therefore, by using a low-performance / low-cost controller, the cost and performance of the main controller 24 and the sub-controller 25 are balanced to reduce the product cost.

  This point will be described more specifically. The main controller 24 A / D converts the amount of reflected light received by the optical fiber 14-2 on the light receiving side, and supplies a predetermined current to the first thermoelectric cooling element 2 based on the A / D conversion value. Control with the control cycle. Further, the mirror surface temperature tPpv detected by the first temperature sensor 12 is A / D converted, and the mirror surface temperature tPpv at every moment is displayed. And the temperature when the dew condensation produced on the mirror surface 11-1 reaches the equilibrium state is displayed as the dew point temperature. On the other hand, the sub-controller 25 performs A / D conversion on the sub-cooler temperature tSpv detected by the second temperature sensor 21, and performs a predetermined control on the current supplied to the second thermoelectric cooling element 18 based on the A / D conversion value. Control by cycle.

  In the main controller 24, A / D conversion of the amount of reflected light received by the light receiving side optical fiber 14-2 is performed by the first A / D converter 24-2, and the first A / D conversion value is used. The CPU 24-1 controls the supply current to one thermoelectric cooling element 2 in a predetermined control cycle. The A / D conversion of the mirror surface temperature tPpv detected by the first temperature sensor 12 is performed by the second A / D converter 24-3. On the other hand, in the sub-controller 25, the A / D conversion of the sub-cooler temperature tSpv detected by the second temperature sensor 21 is performed by the first A / D converter 25-2, and the second based on the A / D conversion value. The CPU 25-1 controls the current supplied to the thermoelectric cooling element 18 at a predetermined control cycle.

  Here, in order to balance the cost and performance of the main controller 24 and the sub-controller 25, the A / D of the first A / D converter 24-2 and the second A / D converter 24-3 in the main controller 24 is used. The accuracy of D conversion is higher than the accuracy of A / D conversion of the first A / D converter 25-2 in the sub-controller 25. Further, the control cycle of the supply current to the first thermoelectric cooling element 2 in the main controller 24 is shorter than the control cycle of the supply current to the second thermoelectric cooling element 18 in the sub-controller 25.

  In the sub-controller 25, the accuracy of the A / D conversion of the second A / D converter 24-3 is approximately the same as that of the first A / D converter 25-2. In this example, for the sake of explanation, the first A / D converter 25-2 and the second A / D converter 25-3 are provided separately, but the first A / D converter 25- 2 and the second A / D converter 25-3, and one A / D converter may be used in a time-sharing manner.

  In this mirror-cooled dew point meter 201, the control period of the supply current from the main controller 24 to the first thermoelectric cooling element 2 is the control period of the supply current from the sub-controller 25 to the second thermoelectric cooling element 18. Although the cycle is shorter, the control of the supply current from the main controller 24 to the first thermoelectric cooling element 2 is proportionally controlled, and the control of the supply current from the sub-controller 25 to the second thermoelectric cooling element 18 is controlled. May be set to ON / OFF control.

  That is, the main controller 24 that controls condensation in an equilibrium state requires high-speed and precise control, and therefore employs proportional control, and the sub-controller 25 that controls the temperature of the sub-cooler may be relatively about control. The control method may be different, such as adopting ON / OFF control that is not high in control performance and can be realized at a low price. Of course, both the main controller 24 / sub-controller 25 may control the supply current by proportional control.

[Normal / abnormal judgment of mirror surface status using the received light intensity reference range]
The CPU 24-1 of the main controller 24 controls the supply current to the first thermoelectric cooling element 2 (dew point temperature) so as to achieve an equilibrium state in which the increase or decrease of the condensation occurring on the mirror surface 11-1 is eliminated as a periodic interrupt processing operation. Measurement control) is interrupted (FIG. 6: step S201).

  Then, after the elapse of a predetermined time (YES in step S202), the light amount (light reception amount) Rpv of the reflected light from the mirror surface 11-1 received through the light receiving side optical fiber 14-2 is obtained (step S203). ). Then, it is checked whether or not the calculated received light amount Rpv is within a predetermined received light amount reference range (step S204).

  That is, after interrupting the dew point temperature measurement control (step S201), the CPU 24-1 waits for the elapse of a predetermined time (step S202) to create a state in which no condensation occurs on the mirror surface 11-1, and the mirror surface at this time The received light amount Rpv of the reflected light from 11-1 is obtained (step S203), and it is checked whether or not the obtained received light amount Rpv is within a predetermined received light amount reference range (step S204).

  If the received light amount Rpv is within the received light amount reference range (YES in step S204), the CPU 24-1 determines that the state of the mirror surface 11-1 is normal, and resumes dew point temperature measurement control ( Step S205).

[Transition to automatic cleaning control]
On the other hand, if the received light amount Rpv is out of the received light amount reference range (NO in step S204), the CPU 24-1 determines that the state of the mirror surface 11-1 is abnormal and adheres to the mirror surface 11-1. In order to remove the condensate that would be present, the current supplied to the first thermoelectric cooling element 2 is controlled so as to raise the temperature of the mirror surface 11-1 (step S206). That is, the dew point temperature measurement control is stopped, and the control proceeds to control of the current supplied to the first thermoelectric cooling element 2 (automatic cleaning control) so as to increase the temperature of the mirror surface 11-1. In this example, the current supplied to the first thermoelectric cooling element 2 is increased to a predetermined current value, and the temperature of the mirror surface 11-1 is increased.

  Then, after elapse of a predetermined time (YES in step S207), N (initial value 0) is set to N = N + 1 (step S208), and it is confirmed that N> Nmax is not satisfied (NO in step S209). The process returns to S203. That is, by waiting for the elapse of a predetermined time, the temperature of the mirror surface 11-1 is increased to a value corresponding to the current value increased in step S206, and the reflection from the mirror surface 11-1 is performed again at the increased temperature. The amount of received light Rpv is obtained.

  In this case, if the dirt adhering to the mirror surface 11-1 is a condensed material, and the condensed material is removed by evaporation or sublimation due to the temperature rise of the mirror surface 11-1, the reflected light from the mirror surface 11-1. The received light amount Rpv falls within the received light amount reference range (YES in step S204), and the CPU 24-1 determines that the state of the mirror surface 11-1 has returned to normal, and resumes dew point temperature measurement control (step S205). .

  On the other hand, if the received light amount Rpv of the reflected light from the mirror surface 11-1 is out of the received light amount reference range (NO in step S204), the CPU 24-1 does not return the state of the mirror surface 11-1 to normal. The current supplied to the first thermoelectric cooling element 2 is increased by a predetermined amount (step S206), and the temperature of the mirror surface 11-1 is further increased.

  Then, after a predetermined time has elapsed (YES in step S207), N = N + 1 is set (step S208). After confirming that N> Nmax is not satisfied (NO in step S209), the process returns to step S203. The received light amount Rpv of the reflected light from the mirror surface 11-1 is obtained again at the raised temperature.

  In the same manner, it is checked whether or not the received light amount Rpv of the reflected light from the mirror surface 11-1 is within the received light amount reference range (step S204). Determining that the state has returned to normal (YES in step S204), restarting dew point temperature measurement control (step S205), and determining that the state of the mirror surface 11-1 has not returned to normal if it is outside the received light amount reference range. Then (NO in step S204), the current supplied to the first thermoelectric cooling element 2 is increased by a predetermined amount (step S206), and the processing operation of further increasing the temperature of the mirror surface 11-1 is repeated.

  In this way, in this mirror-cooled dew point meter 201, when the condensed material is attached to the mirror surface 11-1, the condensed material is evaporated or sublimated at a high speed due to the temperature rise of the mirror surface 11-1, There is no need to manually clean the mirror surface, and there is no need to provide a separate device for removing the condensed material. Moreover, in this mirror surface cooling-type dew point meter 201, when the stain | pollution | contamination adhering to the mirror surface 11-1 is a condensed substance, even if it does not understand the kind of the condensed substance, the process of the temperature rise of the mirror surface 11-1 is carried out. The condensed substance evaporates or sublimes along the way. Therefore, it is possible to return the state of the mirror surface 11-1 to a normal state without specifying the condensed substance in advance.

  When N> Nmax is satisfied during the repeated processing of steps S206 to S209 (YES in step S209), the CPU 24-1 determines that the stain on the mirror surface 11-1 cannot be recovered by the temperature rise, and is abnormal. An alarm is issued (step S210). For example, when dust adheres to the mirror surface 11-1 or the detection system is deteriorated, the temperature cannot be recovered by the temperature rise of the mirror surface 11-1, so that an alarm is issued. This alarm is sent to the host device via the dew point temperature output unit 24-4.

  In the flowchart shown in FIG. 6, after the dew point temperature measurement control is interrupted, the received light amount Rpv of the reflected light from the mirror surface 11-1 after the elapse of a predetermined time is obtained, but the first thermoelectric cooling element 2 After interrupting the control of the supply current to the light source, the change in the mirror surface temperature tPpv from the first temperature sensor 12 is checked, and the amount of reflected light received from the mirror surface 11-1 when the mirror surface temperature tPpv no longer changes Rpv may be obtained.

  FIG. 7 illustrates a flowchart in this case. This flowchart corresponds to FIG. 6. In step S202-1, the change in the mirror surface temperature tPpv is checked, and in step S202-2, the time point at which the change in the mirror surface temperature tPpv no longer occurs is determined. It should be noted that the point in time at which the change in the mirror surface temperature tPpv no longer occurs is determined as the timing when the rate of change in the mirror surface temperature tPpv falls below a predetermined value.

  Further, as shown in FIG. 8, instead of checking the change in the mirror surface temperature tPpv in step S202-1, the received light amount Rpv of the reflected light from the mirror surface 11-1 is checked, and in step S202-2, the received light amount Rpv. It is also possible to determine the point in time when no change occurs. Note that when the change in the amount of received light pv no longer occurs, it is determined as the timing when the rate of change in the amount of received light Rpv falls below a predetermined value.

  In addition, in this mirror surface cooling-type dew point meter 201, the dew condensation (dew point) which arises on the mirror surface 11-1 is detected, However, The frost (frost point) which arises on the mirror surface 11-1 by the same structure is detected. You can also. That is, the frost (frost point) generated on the mirror surface 11-1 is controlled by controlling the supply current to the first thermoelectric cooling element 2 so as to achieve an equilibrium state in which the increase or decrease of the frost generated on the mirror surface 11-1 is eliminated. It is also possible to detect.

  In this mirror-cooled dew point meter 201, the dew point measurement ON / OFF switch 28 and the subcooler control ON / OFF switch 29 are provided separately. However, the dew point measurement ON / OFF switch 28 and the subcooler control ON / OFF are provided. The switch 29 may be constituted by a single switch. In this case, dew point measurement is turned on and subcooler control is turned on simultaneously, and dew point measurement is turned off and subcooler control is turned off simultaneously.

  Further, in this mirror-cooled dew point meter 201, the first thermoelectric cooling element 2 is a one-stage Peltier, but it may be a two-stage Peltier. That is, as long as the size around the mirror surface and responsiveness are sufficient, a configuration in which a multistage Peltier and a subcooler are combined may be used. Further, in the mirror surface cooling type dew point meter 201, the second thermoelectric cooling element 18 is provided, but the second thermoelectric cooling element 18 is not necessarily provided, and only the first thermoelectric cooling element 2 is provided. You may be the structure provided.

  Further, in this mirror-cooled dew point meter 201, for example, as shown in the processing of steps S206 to S209 in FIG. 6, the temperature of the mirror surface 11-1 is gradually increased, but an appropriate temperature (for example, (100 ° C.) may be determined and the temperature may be increased at once. In this case, for example, if the mirror surface 11-1 does not return to a normal state even after a predetermined time has elapsed, an alarm is issued.

  Further, in this mirror-cooled dew point meter 201, as an automatic cleaning control, the thermoelectric cooling element 2 is used so as to raise the temperature of the mirror surface 11-1 in order to remove condensed substances that may have adhered to the mirror surface 11-1. Although the current supplied to is controlled, the pressure in the sampling chamber 31 may be controlled to be reduced in order to remove the condensed material that may have adhered to the mirror surface 11-1.

  When the mirror surface 11-1 is heated to remove the condensed material that would have adhered to the mirror surface 11-1, it is damaged by heat shock. On the other hand, if the condensed substance that would have adhered to the mirror surface 11-1 is removed by reducing the pressure in the sampling chamber 31, there will be no heat shock as in the case of heating and damage will not occur. It becomes possible.

  FIG. 9 shows a flowchart corresponding to FIG. 6 in the case where the pressure in the sampling chamber 31 is controlled to be reduced in order to remove the condensate that may have adhered to the mirror surface 11-1. In this flowchart, the processing from steps S301 to S304 is the same as the processing from steps S201 to S204 in FIG.

  If the received light amount Rpv is out of the received light amount reference range (NO in step S304), the CPU 24-1 determines that the state of the mirror surface 11-1 is abnormal and adheres to the mirror surface 11-1. In order to remove the wax condensate, the gate valve 40 is closed and the operation of the suction pump 41 is continued to reduce the pressure in the sampling chamber 31 (step S306). That is, when the operation of the suction pump 41 is continued, the gate valve 40 is closed to shift to a pressure reduction control (automatic cleaning control) that lowers the pressure in the sampling chamber 31. The gate valve 40 is closed via the CPU 25-1 of the sub-controller 25.

  Then, after elapse of a predetermined time (YES in step S307), N (initial value 0) is set to N = N + 1 (step S309), and after confirming that N> Nmax is not satisfied (NO in step S309), step The process returns to S303. That is, by waiting for the elapse of a predetermined time, the pressure in the sampling chamber 31 is reduced to a predetermined value, and the received light amount Rpv of the reflected light from the mirror surface 11-1 is again set in a state where this pressure is reduced. Ask.

  In this case, if the dirt adhering to the mirror surface 11-1 is a condensed substance and the condensed substance is removed by evaporation or sublimation due to a decrease in the pressure in the sampling chamber 31, the reflection from the mirror surface 11-1. The light reception amount Rpv falls within the light reception amount reference range (YES in step S304), and the CPU 24-1 determines that the state of the mirror surface 11-1 has returned to normal, and continues the operation of the suction pump 41. Thus, the gate valve 40 is opened and the dew point temperature measurement control is resumed (step S305).

  On the other hand, if the received light amount Rpv of the reflected light from the mirror surface 11-1 is out of the received light amount reference range (NO in step S304), the CPU 24-1 does not return to the normal state of the mirror surface 11-1. The passage of a predetermined time is awaited with the gate valve 40 closed (YES in step S307), and the pressure in the sampling chamber 31 is further reduced. In this case, the elapsed time in step S307 is shorter than the first elapsed time, and the amount of decrease in the pressure in the sampling chamber 31 is small. Thereby, the pressure in the sampling chamber 31 decreases to the predetermined value PL at the first time and decreases to PL-α at the second time.

  Then, the CPU 24-1 sets N = N + 1 (step S308), confirms that N> Nmax is not satisfied (NO in step S309), returns to the process in step S303, and again at the increased temperature, the mirror surface 11 The received light amount Rpv of the reflected light from −1 is obtained.

  Similarly, it is checked whether or not the received light amount Rpv of the reflected light from the mirror surface 11-1 is within the received light amount reference range (step S304). Determining that the state has returned to normal (YES in step S304), restarting dew point temperature measurement control (step S305), and determining that the state of the mirror surface 11-1 has not returned to normal if it is outside the received light amount reference range. Then (NO in step S304), the processing operation of reducing the pressure in the sampling chamber 31 by a predetermined amount α (steps S306 and 307) is repeated.

  If N> Nmax is satisfied during the repetitive processing of steps S306 to S309 (YES in step S309), the CPU 24-1 determines that the contamination of the mirror surface 11-1 cannot be recovered by the reduced pressure, and issues an alarm. (Step S310).

  In the flowchart shown in FIG. 9, after interrupting the control of the current supplied to the first thermoelectric cooling element 2, the received light amount Rpv of the reflected light from the mirror surface 11-1 after a lapse of a predetermined time is obtained. As shown in the flowchart of FIG. 10 corresponding to the flowchart of FIG. 7, after the control of the supply current to the first thermoelectric cooling element 2 is interrupted, the change in the mirror surface temperature tPpv from the first temperature sensor 12 is checked. The received light amount Rpv of the reflected light from the mirror surface 11-1 when the mirror surface temperature tPpv no longer changes may be obtained.

  As shown in FIG. 11, instead of checking the change in the mirror surface temperature tPpv in step S302-1, the received light amount Rpv of the reflected light from the mirror surface 11-1 is checked, and in step S302-2, the received light amount Rpv. It is also possible to determine the point in time when no change occurs. Note that when the change in the amount of received light pv no longer occurs, it is determined as the timing when the rate of change in the amount of received light Rpv falls below a predetermined value.

[Functional block diagram of the main part of the mirror-cooled dew point meter]
FIG. 12 shows a functional block diagram of the main part of the above-described mirror-cooled dew point meter 201. In this figure, the same reference numerals as those in FIGS. 1 and 2 denote the same or equivalent components as those described with reference to FIGS. 1 and 2, and the description thereof will be omitted. In this specular cooling type dew point meter 201, the control unit 201B includes a dew point temperature measurement control unit 34, a specular surface abnormal state determination unit 35, an automatic cleaning control unit 36, and a control mode selection unit 37. In addition, when starting dew point measurement, the suction pump 41 is operated and the gate valve 40 is opened, but a control unit for the gate valve 40 and the suction pump 41 is not shown.

  In the control unit 201B, the dew point temperature measurement control unit 34 mirrors the current supplied to the thermoelectric cooling element 2 based on the amount of reflected light from the mirror surface 11-1 received through the light receiving side optical fiber 14-2. 11-1 is controlled so that there is no increase or decrease in dew condensation or frost formation, and the temperature tx1 of the mirror surface 11-1 detected by the temperature sensor 12 in the equilibrium state is taken in and controlled as a dew point temperature measurement value tx1. This is sent to the mode selection unit 37.

  In the control unit 201B, the mirror surface abnormality state determination unit 35 determines whether the state of the mirror surface 11-1 is normal or abnormal based on the amount of reflected light from the mirror surface 11-1 received through the light receiving side optical fiber 14-2. The determination result is sent to the control mode selection unit 37.

  In the control unit 201B, the automatic cleaning control unit 36 supplies current to the thermoelectric cooling element 2 so as to raise the temperature of the mirror surface 11-1 so as to remove the condensed material that may have adhered to the mirror surface 11-1. To control. In this example, the temperature tx1 of the mirror surface 11-1 detected by the temperature sensor 12 is given to the automatic cleaning control unit 36. In this example, a method of increasing the current value supplied to the thermoelectric cooling element 2 is taken. Therefore, the temperature tx1 of the mirror surface 11-1 detected by the temperature sensor 12 is not necessarily required.

  In the control unit 201B, the control mode selection unit 37 instructs the dew point temperature measurement control unit 34 to always execute the dew point temperature measurement control, and periodically interrupts the dew point temperature measurement control to cause a mirror surface abnormality. Whether the state of the mirror surface 11-1 is normal or abnormal is determined by the state determination unit 35, and when the state of the mirror surface 11-1 is abnormal, the automatic cleaning control unit 36 performs automatic cleaning of the mirror surface 11-1. . When the state of the mirror surface 11-1 returns to normal by this automatic cleaning, the control mode selection unit 37 restarts the dew point temperature measurement control by the dew point temperature measurement control unit 34. In addition, during the dew point temperature measurement control by the dew point temperature measurement control unit 34, the control mode selection unit 37 outputs the dew point temperature measurement value tx1 from the dew point temperature measurement control unit 34 to the host device.

  FIG. 13 is a time chart showing changes in the control mode in this mirror-cooled dew point meter 201. The control mode selection unit 37 always executes the dew point temperature measurement control by the dew point temperature measurement control unit 34. During the dew point temperature measurement control (period T1), the control mode selection unit 37 periodically interrupts this dew point temperature measurement control, and the mirror surface abnormal state determination unit 35 determines whether the mirror surface 11-1 is normal or abnormal. Execute (t1, t2, t3 points). Here, for example, when it is determined that the state of the mirror surface 11-1 is abnormal at the point t3, the control mode selection unit 37 stops the dew point temperature measurement control by the dew point temperature measurement control unit 34, and performs automatic cleaning. The control unit 36 shifts to automatic cleaning control. Then, after the transition to the automatic cleaning control, when the mirror surface abnormal state determination unit 35 confirms that the state of the mirror surface 11-1 has returned to normal (point t4), the control mode selection unit 37 performs dew point temperature measurement. The dew point temperature measurement control by the control unit 34 is resumed.

  In this mirror-cooled dew point meter 201, when it is determined that the state of the mirror surface 11-1 is abnormal, automatic cleaning control is performed in order to remove condensed substances that may have adhered to the mirror surface 11-1. Therefore, it is not necessary to manually clean the mirror surface 11-1, and it is possible to eliminate the need to separately provide a device for removing condensed substances. However, this mirror-cooled dew point meter 201 alone must stop (stop) the dew point temperature measurement control and heat the mirror surface 11-1 in order to perform automatic cleaning control. For this reason, as shown as period T2 in FIG. 13, a period during which the dew point temperature cannot be measured occurs. That is, a period during which humidity cannot be measured occurs.

[Humidity measurement system]
Therefore, in the humidity measurement system of the present embodiment, a mirror-cooled dew point meter and a humidity sensor that measures humidity based on a principle different from this mirror-cooled dew point meter are provided. The humidity measurement value obtained by converting is used as the main sensor that is always used as the effective humidity measurement value (the official humidity measurement value of the gas to be measured), and the humidity sensor has its humidity when the main sensor is in automatic cleaning control. The measurement value is an auxiliary sensor that is used as an effective humidity measurement value (formal humidity measurement value of the gas to be measured). As a result, high-precision humidity measurement is usually performed by the main sensor (mirror-cooled dew point meter), and the auxiliary sensor (humidity sensor) is used when the measurement accuracy drops due to the mirror surface of the main sensor becoming dirty. As a result, humidity measurement is performed, and humidity measurement is continuously performed without interruption. That is, the period T2 during which humidity cannot be measured does not occur.

[Embodiment 1]
FIG. 14 shows a functional block diagram of the main part of the first embodiment (Embodiment 1) of the humidity measurement system according to the present invention. In this humidity measurement system, a humidity sensor 202 that measures humidity based on a principle different from that of the mirror-cooled dew point meter 201 is provided in addition to the mirror-cooled dew point meter 201.

  In the specular cooling type dew point meter 201, the control unit 201B includes a dew point temperature measurement control unit 34, a specular surface abnormal state determination unit 35, an automatic cleaning control unit 36, and a control mode selection unit 37.

  The humidity sensor 202 includes a humidity sensing element 202A and a detection signal generation unit 202B, and the detection signal generation unit 202B generates a signal corresponding to the humidity detected by the humidity sensing element 202A as a detection signal.

  A gate valve 40-1 and a suction pump 41-1 are provided for the mirror-cooled dew point meter 201, and a gate valve 40-2 and a suction pump 41-2 are provided for the humidity sensor 202. ing. Although control units for the gate valves 40-1 and 40-2 and the suction pumps 41-1 and 41-2 are not shown, the suction pumps 41-1 and 41-2 are operated to start the humidity measurement. When the valves 40-1 and 40-2 are opened, the gas to be measured is branched and supplied to the sampling chamber 31 of the mirror-cooled dew point meter 201 and the humidity sensing element 202 </ b> A of the humidity sensor 202. In other words, in the present embodiment, the mirror-cooled dew point meter 201 and the humidity sensor 202 are installed in parallel, and the measurement gas having the same supply source is sent simultaneously to the sampling chamber 31 and the humidity sensing element 202A. .

  In this humidity measurement system, an overall controller 300 is provided for the mirror-cooled dew point meter 201 and the humidity sensor 202. The overall controller 300 includes a dew point meter control mode designating unit 301, a humidity measurement value selecting unit 302, a dew point meter current control mode recognizing unit 303, a mirror surface state determination result recognizing unit 304, and a dew point temperature / humidity converting unit 305. I have.

  In the specular cooling type dew point meter 201, the control mode selection unit 37 receives the control mode specification (signal D 1) from the dew point meter control mode specifying unit 301 of the overall controller 300, and the current control mode in the specular cooling type dew point meter 201. Is set to the dew point temperature measurement control mode or the automatic cleaning control mode. The control mode selection unit 37 sends the currently selected control mode (signal B1) to the dew point meter current control mode recognition unit 303 of the overall controller 300. Further, the control mode selection unit 37 sends the dew point temperature measurement value tx1 (signal A1) from the dew point temperature measurement control unit 34 to the dew point temperature / humidity conversion unit 305 of the overall controller 300. In the mirror-cooled dew point meter 201, the mirror surface state determination unit 35 uses the mirror surface of the overall controller 300 instead of its own control mode selection unit 37 to determine whether the mirror surface 11-1 is normal or abnormal (signal C1). It is sent to the state judgment result recognition unit 304.

  In the humidity sensor 202, the humidity sensing element 202A detects the humidity of the gas to be measured that is branched and supplied to the specular cooling dew point meter 201, and the detection signal generation unit 202B corresponds to the humidity detected by the humidity sensing element 202A. A signal is generated as a detection signal. The detection signal generated by the detection signal generation unit 202B is sent to the humidity measurement value selection unit 302 of the overall controller 300 as the humidity measurement value X2 of the measurement gas measured by the humidity sensor 202.

  The dew point meter current control mode recognition unit 303 of the overall controller 300 recognizes the currently selected control mode (signal B1) sent from the mirror-cooled dew point meter 201 and uses the recognition result as a dew point meter control mode designation unit. The information is sent to 301 and notified to the host device.

  The specular state determination result recognition unit 304 of the overall controller 300 recognizes the specular state determination result (signal C 1) sent from the specular cooling type dew point meter 201 and sends the recognition result to the dew point meter control mode designation unit 301. At the same time, it notifies the host device.

  The dew point temperature / humidity conversion unit 305 of the overall controller 300 converts the dew point temperature measurement value tx1 (signal A1) sent from the mirror-cooled dew point meter 201 into humidity using a calculation formula, and the converted humidity. Is sent to the humidity measurement value selection unit 302 as the humidity measurement value X1.

  The dew point meter control mode designating unit 301 of the overall controller 300 recognizes the recognition result (B1) of the control mode currently selected in the specular cooling type dew point meter 201 from the dew point meter current control mode recognition unit 303 and recognizes the specular state determination result. The control mode (D1) designated for the specular cooling type dew point meter 201 is determined from the recognition result (C1) of normal / abnormality of the specular state in the specular cooling type dew point meter 201 from the unit 304, and the current effective A sensor (mirror-cooled dew point meter 201 / humidity sensor 202) to be selected as an effective humidity measurement value is notified to the humidity measurement value selection unit 302 (signal E).

  The humidity measurement value selection unit 302 of the overall controller 300 includes a humidity measurement value (first humidity measurement value) X 1 from the dew point temperature / humidity conversion unit 305 from the mirror-cooled dew point meter 201 and humidity measurement from the humidity sensor 202. Value (second humidity measurement value) X2 is input, the humidity measurement value from the effective sensor notified from the dew point control mode designating unit 301 is selected as the effective humidity measurement value, and the selected humidity measurement value Is notified to the host device as an official humidity measurement value of the gas to be measured (measurement humidity of the humidity measurement system) (signal F).

  The dew point meter control mode specifying unit 301 of the overall controller 300 uses the mirror-cooled dew point meter 201 as a main sensor that always uses the measured humidity value obtained by converting the measured dew point temperature as an effective measured value. The humidity sensor 202 is an auxiliary sensor that uses the humidity measurement value as an effective measurement value when the main sensor is in automatic cleaning control, and the dew point temperature measurement control mode is designated as the control mode for the mirror-cooled dew point meter 201. If it is, the humidity measurement value selection unit 302 is notified of the specular cooling type dew point meter 201 as an effective sensor, and the automatic cleaning control mode is designated as the control mode for the specular cooling type dew point meter 201. In this case, the humidity sensor 202 is notified to the humidity measurement value selection unit 302 as an effective sensor. However, as a special condition, the dew point meter control mode designating unit 301 determines the humidity measurement value during a predetermined time T1 until the dew point temperature measurement control is stabilized at the time of transition from the automatic cleaning control mode to the dew point temperature measurement control mode. The humidity sensor 202 is notified to the selection unit 302 as an effective sensor.

[Operation]
FIGS. 15A and 15B are time charts showing changes in the control mode and the measurement state of the humidity sensor 202 in the specular cooling dew point meter 201 during operation of the humidity measurement system of the first embodiment.

  The dew point meter control mode designating unit 301 of the overall controller 300 first uses the specular cooling dew point meter 201 as a main sensor, the humidity sensor 202 as an auxiliary sensor, and the specular cooling type dew point meter 201 to the humidity measurement value selection unit 302. As a valid sensor. In other words, the mirror-cooled dew point meter 201 can measure humidity with higher accuracy than the humidity sensor 202 from the measurement principle, and the mirror-cooled dew point meter 201 capable of measuring humidity with higher accuracy. As an effective sensor. Hereinafter, the mirror-cooled dew point meter 201 serving as a main sensor is referred to as a main sensor, and the humidity sensor 202 serving as an auxiliary sensor is referred to as a sub sensor.

  The control mode selection unit 37 of the main sensor 201 always executes the dew point temperature measurement control by the dew point temperature measurement control unit 34, and the sub sensor 202 always keeps the measurement state.

  FIG. 16 shows a control flowchart of the main sensor 201 in the humidity measurement system of the first embodiment, and FIG. 17 shows a control flowchart of the overall controller 300.

  The control mode selection unit 37 of the main sensor 201 periodically interrupts the dew point temperature measurement control during the dew point temperature measurement control, and determines whether the mirror surface abnormality state determination unit 35 determines the normal / abnormal state of the mirror surface 11-1. Execute (t1, t2, t3 points). That is, the control mode selection unit 37 confirms the current self control mode (FIG. 16: step S401), and since the current self control mode is dew point temperature measurement control (YES in step S402), the mirror surface state is determined. It is checked whether or not it is the confirmation timing (step S403), and if it is the mirror surface state confirmation timing (YES in step S403), the dew point temperature measurement control is interrupted and the state (normal / abnormal) of the mirror surface 11-1 is confirmed. (Step S404).

  When the mirror surface abnormal state determination unit 35 of the main sensor 201 confirms that the state of the mirror surface 11-1 is normal (YES in step S405), the mirror controller 11- notifies the general controller 300 to that effect (step S407). If it is confirmed that the state 1 is abnormal (NO in step S405), the control unit 300 is notified of this (step S406). In addition, during the dew point temperature measurement control, when the mirror surface state confirmation timing is not reached (NO in step S403), the control mode selection unit 37 of the main sensor 201 supervises the dew point temperature measurement value tx1 from the dew point temperature measurement control unit 34. The controller 300 is notified (step S408).

  On the other hand, the sub sensor 202 continues to detect the humidity of the gas to be measured that is branched to the main sensor 201 and continues to send the humidity measurement value X2 to the humidity measurement value selection unit 302 of the overall controller 300.

  The dew point meter control mode designation unit 301 of the overall controller 300 confirms the current control mode of the main sensor 201 from the recognition result from the dew point meter current control mode recognition unit 303 (FIG. 17: step S501). In this case, since the current control mode of the main sensor 201 is the dew point temperature measurement control mode (YES in step S502), the state of the mirror surface 11-1 of the main sensor 201 is determined based on the recognition result from the mirror surface state determination result recognition unit 304. Is confirmed (step S503).

[When the state of the mirror surface of the main sensor is normal]
Now, at the points t1 and t2 shown in FIG. 15A, if the main sensor 201 sends a determination result indicating that the state of the mirror surface 11-1 is normal (YES in step S504), the dew point is reached. The meter control mode designation unit 301 notifies the humidity measurement value selection unit 302 of the main sensor 201 as an effective sensor. Accordingly, the humidity measurement value selection unit 302 selects the humidity measurement value X1 from the main sensor 201 via the dew point temperature / humidity conversion unit 305 as an effective humidity measurement value, and the selected humidity measurement value X1 is the humidity measurement system. Is continuously notified to the host device as the measured humidity (official humidity measurement value at normal time) (step S505).

[When the mirror surface of the main sensor is abnormal]
If the determination result that the state of the mirror surface 11-1 is abnormal is sent from the main sensor 201 at the point t3 shown in FIG. 15A (NO in step S504), the dew point meter control mode The designation unit 301 sends a switching command to the main sensor 201 so as to shift the control mode to the automatic cleaning control mode (step S506).

  The control mode selection unit 37 of the main sensor 201 receives the switching command to the automatic cleaning control mode from the dew point meter control mode designating unit 301 of the overall controller 300 and automatically cleans the control mode from the previous dew point temperature measurement control mode. Switch to the control mode (point t3 shown in FIG. 15A). In other words, the dew point temperature measurement control up to that point is stopped, and the process shifts to automatic cleaning control.

The dew point meter control mode designation unit 301 switches the control mode of the main sensor 201 to the automatic cleaning control mode, and then notifies the humidity measurement value selection unit 302 of the sub sensor 202 as an effective sensor. As a result, the humidity measurement value selection unit 302 selects the humidity measurement value X2 from the sub sensor 202 as an effective humidity measurement value, and uses the selected humidity measurement value X2 as the measured humidity (formal humidity at the time of abnormality) of the humidity measurement system. Notification to the host device is started as a measurement value) (step S507).

  The control mode selection unit 37 of the main sensor 201 periodically performs automatic cleaning of the mirror surface 11-1 as automatic cleaning control, and the mirror surface abnormal state determination unit 35 normalizes the state of the mirror surface 11-1 after the cleaning. / Make judgment of abnormality. The mirror surface abnormal state determination unit 35 notifies the overall controller 300 of the normal / abnormal determination result (step S409).

  The dew point meter control mode designating unit 301 of the overall controller 300 confirms the current control mode of the main sensor 201 from the recognition result from the dew point meter current control mode recognition unit 303 (step S501). In this case, since the current control mode of the main sensor 201 is the automatic cleaning control mode (NO in step S502), the dew point meter control mode designating unit 301 uses the sub sensor 202 as an effective sensor for the humidity measurement value selecting unit 302. Notify as. Accordingly, the humidity measurement value selection unit 302 notifies the host device of the humidity measurement value X2 from the sub sensor 202 as the measurement humidity of the humidity measurement system (step S508).

  During the automatic cleaning control of the main sensor 201, the dew point meter control mode designation unit 301 confirms the state of the mirror surface 11-1 of the main sensor 201 from the recognition result from the mirror surface state determination result recognition unit 304 (step S509, 510), the sub sensor 202 is continuously notified to the humidity measurement value selection unit 302 as an effective sensor (step S508).

[When the mirror status of the main sensor returns to normal]
If the determination result that the state of the mirror surface 11-1 is normal is sent from the main sensor 201 at the point t4 shown in FIG. 15 (a) (YES in step S510), the dew point meter control is performed. The mode designation unit 301 sends a switching command to the main sensor 201 so as to shift the control mode to the dew point temperature measurement control mode (step S511).

  The control mode selection unit 37 of the main sensor 201 receives a switching command to the dew point temperature measurement control mode from the dew point meter control mode designating unit 301 of the overall controller 300, and changes the control mode from the automatic cleaning control mode so far to the dew point temperature. Switch to the measurement control mode (point t4 shown in FIG. 15A). That is, the automatic cleaning control so far is stopped and the dew point temperature measurement control is restored.

  The dew point meter control mode designating unit 301 of the overall controller 300 switches the control mode of the main sensor 201 from the automatic cleaning control mode to the dew point temperature measurement control mode, and then a predetermined time T1 elapses until the dew point temperature measurement control is stabilized. Until (YES in step S512), the humidity sensor value selection unit 302 is notified of the sub sensor 202 as an effective sensor. As a result, the humidity measurement value selection unit 302 continues to measure the humidity measurement value X2 from the sub sensor 202 until the predetermined time T1 until the dew point temperature measurement control is stabilized even after the automatic cleaning control of the main sensor 201 is completed. Is continuously notified to the host device as the measurement humidity of the humidity measurement system (step S513).

  When a predetermined time T1 has elapsed until the dew point temperature measurement control is stabilized (YES in step S512), the dew point meter control mode designating unit 301 determines the current state of the main sensor 201 from the recognition result from the dew point meter current control mode recognition unit 303. The control mode is confirmed (step S501). In this case, since the current control mode of the main sensor 201 has been returned to the dew point measurement control mode (YES in step S502) and the state of the mirror surface 11-1 is also normal (YES in step S504), dew point meter control is performed. The mode designation unit 301 notifies the humidity measurement value selection unit 302 of the main sensor 201 as an effective sensor. Accordingly, the humidity measurement value selection unit 302 selects the humidity measurement value X1 from the main sensor 201 via the dew point temperature / humidity conversion unit 305 as an effective humidity measurement value, and the selected humidity measurement value X1 is the humidity measurement system. Is notified to the host device as the measured humidity (step S505).

  As described above, in the first embodiment, the main sensor 201 normally performs high-precision humidity measurement, and when it is determined that the state of the mirror surface 11-1 of the main sensor 201 is abnormal, that is, the main sensor 201 When the reliability of the humidity measurement value X1 by 201 is denied, the humidity measurement is performed by the sub sensor 202 that measures humidity based on a principle different from that of the main sensor 201, and the humidity measurement is continuously performed without interruption. .

  In the first embodiment, after the automatic cleaning control is completed, the main sensor 201 returns to the dew point temperature measurement control (step S511), and a predetermined time T1 has elapsed until the dew point temperature measurement control is stabilized (step S511). When YES in S512, the mirror surface state determination result recognition unit 304 confirms that the state of the mirror surface 11-1 has returned to normal (YES in Step S504), that is, the reliability of the humidity measurement value X1 by the main sensor 201. Is affirmed, the humidity measurement value X1 from the main sensor 201 via the dew point temperature / humidity conversion unit 305 is used as an effective humidity measurement value, and high-precision humidity measurement by the main sensor 201 is continued.

  That is, while the automatic cleaning control is performed in the main sensor 201 and until the dew point temperature measurement control is stabilized after the transition from the automatic cleaning control to the dew point temperature measurement control, the humidity measurement by the sub sensor 202 is performed. During other periods, high-precision humidity measurement is performed by the main sensor 201, and high-precision humidity measurement is always continued as a whole.

[Embodiment 2]
FIG. 18 shows a functional block diagram of the main part of the second embodiment (Embodiment 2) of the humidity measurement system according to the present invention. In this figure, the same reference numerals as those in FIG. 14 denote the same or equivalent components as those described with reference to FIG.

  The difference of the second embodiment from the first embodiment is that the specular state determination unit 35 is eliminated from the specular cooling type dew point meter 201, and the specular state determination unit 306 is replaced with the specular state determination result recognition unit 304 of the overall controller 300. It is in the point provided. The specular state determination unit 306 includes a humidity measurement value (first humidity measurement value) X1 from the dew point temperature / humidity conversion unit 305 from the mirror surface cooling type dew point meter 201 and a humidity measurement value (second humidity) from the humidity sensor 202. Measurement value) X2 is input, and the normal / abnormal state of the mirror surface 11-1 of the mirror-cooled dew point meter 201 is determined based on the difference between the humidity measurement values X1 and X2, and the determination result is controlled by the dew point meter. The data is sent to the mode designation unit 301.

  In the humidity measurement system according to the second embodiment, the dew point control mode designating unit 301 of the overall controller 300 uses the specular cooling type dew point meter 201 to obtain a humidity measurement value obtained by converting the measured dew point temperature. The main sensor that is always used as the effective humidity measurement value (the official humidity measurement value of the gas to be measured), and the humidity sensor 202 is the effective humidity measurement value (when the main sensor is under automatic cleaning control) When the dew point temperature measurement control mode is designated as the control mode for the mirror-cooled dew point meter 201 as an auxiliary sensor used as the official humidity measurement value of the gas to be measured, the humidity measurement value selection unit 302 Mirror surface dew point meter 201 is notified as an effective sensor, and automatic cleaning control is performed as a control mode for mirror surface dew point meter 201. If you specify a over de notifies the humidity sensor 202 as a valid sensor against humidity measurement value selecting section 302. However, as a special condition, the dew point meter control mode designating unit 301 determines the humidity measurement value during a predetermined time T1 until the dew point temperature measurement control is stabilized at the time of transition from the automatic cleaning control mode to the dew point temperature measurement control mode. The humidity sensor 202 is notified to the selection unit 302 as an effective sensor.

[Operation]
FIGS. 19A and 19B are time charts showing changes in the control mode and the measurement state of the humidity sensor 202 in the specular cooling dew point meter 201 during operation of the humidity measurement system of the second embodiment.

  The dew point meter control mode designating unit 301 of the overall controller 300 first uses the specular cooling dew point meter 201 as a main sensor, the humidity sensor 202 as an auxiliary sensor, and the specular cooling type dew point meter 201 to the humidity measurement value selection unit 302. As a valid sensor. In other words, the mirror-cooled dew point meter 201 can measure humidity with higher accuracy than the humidity sensor 202 from the measurement principle, and the mirror-cooled dew point meter 201 capable of measuring humidity with higher accuracy. As a valid sensor. Hereinafter, the mirror-cooled dew point meter 201 serving as a main sensor is referred to as a main sensor, and the humidity sensor 202 serving as an auxiliary sensor is referred to as a sub sensor.

  The control mode selection unit 37 of the main sensor 201 always executes the dew point temperature measurement control by the dew point temperature measurement control unit 34, and the sub sensor 202 always keeps the measurement state.

[When the state of the mirror surface of the main sensor is normal]
The control mode selection unit 37 of the main sensor 201 always executes the dew point temperature measurement control by the dew point temperature measurement control unit 34. On the other hand, the sub sensor 202 continues to detect the humidity of the gas to be measured that is branched to the main sensor 201 and continues to send the humidity measurement value X2 to the humidity measurement value selection unit 302 of the overall controller 300.

  During the dew point temperature measurement control of the main sensor 201, the dew point meter control mode designation unit 301 of the overall controller 300 notifies the humidity measurement value selection unit 302 of the main sensor 201 as an effective sensor. Accordingly, the humidity measurement value selection unit 302 selects the humidity measurement value X1 from the main sensor 201 via the dew point temperature / humidity conversion unit 305 as an effective humidity measurement value, and the selected humidity measurement value X1 is the humidity measurement system. The measured humidity is notified to the host device.

  Further, the mirror surface state determination unit 306 of the overall controller 300 performs the humidity measurement value X1 from the main sensor 201 via the dew point temperature / humidity conversion unit 305 and the humidity measurement value X2 from the sub sensor 202 during the dew point temperature measurement control of the main sensor 201. And the normal / abnormal state of the mirror surface 11-1 of the main sensor 201 is determined based on the difference between the humidity measurement values X1 and X2. In this example, the difference between the humidity measurement value X1 and the humidity measurement value X2 is obtained, and when the deviation exceeds a predetermined value, it is determined that the state of the mirror surface 11-1 of the main sensor 201 is abnormal.

  The mirror-cooled dew point meter can measure humidity with higher accuracy than other humidity sensors with different measurement principles, but the deterioration of measurement accuracy due to mirror contamination is faster than humidity sensors with different measurement principles. For this reason, the main sensor 201 is compared by comparing the humidity measurement value X1 by the main sensor 201 which is a mirror-cooled dew point meter with the measurement value of the humidity measurement value X2 from the sub sensor 202 which is another humidity sensor having a different measurement principle. The degree of deterioration can be easily confirmed. Based on such knowledge, in the present embodiment, the deviation of the humidity measurement value X1 from the humidity measurement value X2 is obtained, and when this deviation exceeds a predetermined value, the state of the mirror surface 11-1 of the main sensor 201 is abnormal. Judging that there is.

[When the mirror surface of the main sensor is abnormal]
Now, at the point t1 shown in FIG. 19A, when the mirror surface state determination unit 306 of the overall controller 300 determines that the state of the mirror surface 11-1 of the main sensor 201 is abnormal, the dew point meter control mode is designated. The unit 301 sends a switching command to the main sensor 201 so as to shift the control mode to the automatic cleaning control mode.

  The control mode selection unit 37 of the main sensor 201 receives the switching command to the automatic cleaning control mode from the dew point meter control mode designating unit 301 of the overall controller 300 and automatically cleans the control mode from the previous dew point temperature measurement control mode. Switch to the control mode (point t1 shown in FIG. 19A). In other words, the dew point temperature measurement control up to that point is stopped, and the process shifts to automatic cleaning control.

  The dew point meter control mode designating unit 301 of the overall controller 300 notifies the humidity sensor value selection unit 302 of the sub sensor 202 as an effective sensor after switching the control mode of the main sensor 201 to the automatic cleaning control mode. As a result, the humidity measurement value selection unit 302 selects the humidity measurement value X2 from the sub sensor 202 as an effective humidity measurement value, and starts to notify the host device of the selected humidity measurement value X2 as the measurement humidity of the humidity measurement system. .

  The dew point meter control mode designating unit 301 of the overall controller 300, when the main sensor 201 is switched from the control mode to the automatic cleaning control mode, at the time when a predetermined time T has elapsed (point t2 shown in FIG. 19A), A switching command is sent to the sensor 201 so as to shift the control mode to the dew point temperature measurement control mode.

  Note that the predetermined time T in this case is determined as a predetermined time T sufficient to remove condensed substances that may be attached to the mirror surface 11-of the main sensor 201.

  The dew point meter control mode designating unit 301 keeps reporting the sub sensor 202 as an effective sensor to the humidity measurement value selecting unit 302 while the predetermined time T elapses. As a result, while the main sensor 201 is performing the automatic cleaning control, the humidity measurement value selection unit 302 continues to notify the host device of the humidity measurement value X2 from the sub sensor 202 as the measurement humidity of the humidity measurement system.

[When the mirror status of the main sensor returns to normal]
The control mode selection unit 37 of the main sensor 201 receives a switching command to the dew point temperature measurement control mode from the dew point meter control mode designating unit 301 of the overall controller 300, and changes the control mode from the automatic cleaning control mode so far to the dew point temperature. Switch to the measurement control mode (point t2 shown in FIG. 19A). That is, the automatic cleaning control so far is stopped and the dew point temperature measurement control is restored.

  The dew point meter control mode designating unit 301 of the overall controller 300 switches the control mode of the main sensor 201 from the automatic cleaning control mode to the dew point temperature measurement control mode, and then a predetermined time T1 elapses until the dew point temperature measurement control is stabilized. Until this, the sub sensor 202 is continuously notified to the humidity measurement value selection unit 302 as an effective sensor. As a result, the humidity measurement value selection unit 302 continues to measure the humidity measurement value X2 from the sub sensor 202 until the predetermined time T1 until the dew point temperature measurement control is stabilized even after the automatic cleaning control of the main sensor 201 is completed. Is continuously notified to the host device as the measurement humidity of the humidity measurement system.

  When a predetermined time T <b> 1 elapses until the dew point temperature measurement control is stabilized, the dew point meter control mode designation unit 301 confirms the current control mode of the main sensor 201 from the recognition result from the dew point meter current control mode recognition unit 303. . In this case, since the current control mode of the main sensor 201 is returned to the dew point measurement control mode, the dew point meter control mode designating unit 301 determines that the state of the mirror surface 11-1 of the main sensor 201 from the mirror surface state determination unit 306 is The main sensor 201 is notified to the humidity measurement value selection unit 302 as an effective sensor after confirming the determination result indicating that it has returned to normal. Accordingly, the humidity measurement value selection unit 302 selects the humidity measurement value X1 from the main sensor 201 via the dew point temperature / humidity conversion unit 305 as an effective humidity measurement value, and the selected humidity measurement value X1 is the humidity measurement system. It starts to notify the host device as the measured humidity.

  As described above, in the second embodiment, when the main sensor 201 normally performs highly accurate humidity measurement and it is determined that the state of the mirror surface 11-1 of the main sensor 201 is abnormal, that is, the main sensor 201 When the reliability of the humidity measurement value X1 by 201 is denied, the humidity measurement is performed by the sub sensor 202 that measures humidity based on a principle different from that of the main sensor 201, and the humidity measurement is continuously performed without interruption. .

  In the second embodiment, after completion of the automatic cleaning control for a predetermined time T, the main sensor 201 returns to the dew point temperature measurement control, and a predetermined time T1 elapses until the dew point temperature measurement control is stabilized. When the state determination unit 306 confirms that the state of the mirror surface 11-1 has returned to the normal state, that is, when the reliability of the humidity measurement value X1 by the main sensor 201 is affirmed, the dew point temperature / The humidity measurement value X1 via the humidity conversion unit 305 is used as an effective humidity measurement value, and high-precision humidity measurement by the main sensor 201 is continued.

  That is, while the automatic cleaning control is performed in the main sensor 201 and until the dew point temperature measurement control is stabilized after the transition from the automatic cleaning control to the dew point temperature measurement control, the humidity measurement by the sub sensor 202 is performed. During other periods, high-precision humidity measurement is performed by the main sensor 201, and high-precision humidity measurement is always continued as a whole.

  In the second embodiment, in the main sensor 201, the main sensor 201 is based on the difference between the humidity measurement value X1 from the main sensor 201 via the dew point temperature / humidity conversion unit 305 and the humidity measurement value X2 from the sub sensor 202. Since the normal / abnormal state of the mirror surface 11-1 is determined, humidity measurement can be performed without interruption even during dew point temperature measurement control.

  In the first and second embodiments described above, the automatic cleaning control in the mirror-cooled dew point meter 201 is a heating control method for heating the mirror surface, but a pressure reduction control method for reducing the pressure in the sampling chamber may be used.

  In the first and second embodiments described above, the gate valve 40-1 is provided on the upstream side of the sampling chamber 31, the suction pump 41-1 is provided on the downstream side, the gate valve 40-1 is opened, and the suction pump 41 is provided. The gas to be measured is caused to flow into the sampling chamber 31 by operating -1. However, the pressure to be measured is increased in the sampling chamber 31 by increasing the upstream pressure without providing a suction pump. It is good also as a structure which flows in. In such a configuration, for example, a valve is provided above and downstream of the sampling chamber 31, a pump for decompression is provided near the sampling chamber 31, a valve at the upstream and downstream is closed, and the pump for decompression is operated. The pressure in the sampling chamber 31 can be reduced.

  In the first and second embodiments, the mirror-cooled dew point meter 201 and the humidity sensor 202 are installed in parallel. However, they may be installed in series. FIG. 20 shows a configuration example when a mirror-cooled dew point meter 201 and a humidity sensor 202 are installed in series. When installed in series, automatic cleaning control in the mirror-cooled dew point meter 201 is a heating control method.

  In the first and second embodiments described above, the overall controller 300 is provided for the mirror-cooled dew point meter 201 and the humidity sensor 202. However, the function of the overall controller 300 is given to the mirror-cooled dew point meter 201. You may do it.

  Further, in Embodiments 1 and 2 described above, the dew point temperature / humidity conversion unit 305 is provided in the overall controller 300, but may be provided in the mirror-cooled dew point meter 201. In this case, the mirror-cooled dew point meter 201 is a humidity sensor that measures humidity based on a principle different from that of the humidity sensor 202, and the mirror-cooled dew point meter according to the present invention is incorporated in the humidity sensor. .

  In the first and second embodiments described above, the reliability determination means in the present invention corresponds to the mirror surface state determination unit 35 (FIG. 14) and the mirror surface state determination unit 306 (FIG. 18). The determination of the reliability of the humidity measurement value X1 by the meter 201 is not necessarily based on the mirror surface state. For example, in the mirror surface state determination unit 306 according to the second embodiment, even if the state of the mirror surface 11-1 of the mirror surface cooling type dew point meter 201 is normal, the difference between the humidity measurement values X1 and X2 is caused by other factors. It can grow. In this case, even if the state of the mirror surface 11-1 is normal, it is considered that the measurement accuracy of the mirror surface cooling type dew point meter 201 is lowered, and the humidity measurement value X2 from the humidity sensor 202 is selected as an effective humidity measurement value. It will be a thing.

  In the first and second embodiments described above, after the transition from the automatic cleaning control to the dew point temperature measurement control, a predetermined time T1 is provided until the dew point temperature measurement control is stabilized, and the humidity sensor 202 is also provided during this predetermined time T1. The humidity measurement value X2 from is used as an effective humidity measurement value, but the time until the dew point temperature measurement control is stabilized may not be a problem, and the predetermined time T1 may not necessarily be provided. In addition, it is confirmed that the dew point temperature measurement control is stabilized from the amount of received light reflected from the mirror surface 11-1, and the humidity measurement value X1 from the mirror surface cooling type dew point meter 201 via the dew point temperature / humidity conversion unit 305 is effective. It may be used as a humidity measurement value.

  The humidity measurement system of the present invention is a humidity measurement system that uses a mirror-cooled dew point meter using a thermoelectric cooling element (Peltier element) and a humidity sensor that measures humidity based on a principle different from this mirror-cooled dew point meter. It can be used for humidity measurement of various gases to be measured.

  DESCRIPTION OF SYMBOLS 201 ... Mirror surface cooling type dew point meter, 201A ... Sensor part, 201B ... Control part, 2 ... 2nd thermoelectric cooling element (Peltier element), 2-1 ... Cooling surface, 2-2 ... Heating surface, 11 ... Mirror, 11 DESCRIPTION OF SYMBOLS -1 ... Front surface (mirror surface), 11-2 ... Back surface, 12 ... 2nd temperature sensor, 13 ... Sensor body, 13a ... Front-end | tip part, 13b ... Inclined surface, 13c ... Rear end part, 14 ... Light emitting / receiving integrated type Optical fiber, 14-1 ... Optical fiber on the light-projecting side, 14-2 ... Optical fiber on the light-receiving side, 15 ... Cooling block, 16 ... Cooling plate, 17 ... Thermal conductor, 18 ... Second thermoelectric cooling element (Peltier Element), 18-1 ... cooling surface, 18-2 ... heating surface, 19 ... heat sink, 19a ... radiation fin, 20 ... cooling fan, 21 ... second temperature sensor, 22 ... photoelectric converter, 23 ... outside temperature sensor DT ... detection unit SC ... subcooler 24 ... In-controller, 24-1 ... CPU, 24-2 ... second A / D converter, 24-3 ... second A / D converter, 24-4 ... dew point temperature output unit, 24-5 ... AM, 24-6 ... OM, 25 ... Sub-controller, 25-1 ... CPU, 25-2 ... Second A / D converter, 25-3 ... Second A / D converter, 25-4 ... AM, 25 -5 ... OM, 26 ... power supply, 27 ... power switch, 28 ... dew point measurement ON / OFF switch, 29 ... subcooler control ON / OFF switch, 30 ... subcooler low temperature / high temperature / interlocking selector switch, 31 ... sampling chamber, 34 DESCRIPTION OF SYMBOLS Dew point temperature measurement control part 35 ... Automatic cleaning control part 36 ... Mirror surface state judgment part, 37 ... Control mode selection part, 40 (40-1, 40-2) ... Gate valve, 41 (41-1, 41- 2) Suction pump, 20 DESCRIPTION OF SYMBOLS ... Humidity sensor 202A ... Humidity sensing element 202B ... Detection signal generation part 300 ... General controller 301 ... Dew point meter control mode designation part 302 ... Dew point temperature measurement value selection part 303 ... Dew point meter current control mode recognition part, 304: Mirror surface state determination result recognition unit, 305 ... Dew point temperature / humidity conversion unit, 306 ... Mirror surface state determination unit.

Claims (9)

A mirror surface exposed to the gas to be measured;
A thermoelectric cooling element for cooling the mirror surface;
A temperature sensor for detecting the temperature of the mirror surface;
A light projecting means for irradiating the mirror surface with light;
A light receiving means for receiving a reflected light of the light emitted from the light projecting means to the mirror surface;
Control means for controlling the current supplied to the thermoelectric cooling element based on the amount of reflected light received by the light receiving means,
The control means includes
Based on the amount of reflected light received by the light receiving means, the current supplied to the thermoelectric cooling element is controlled to be in an equilibrium state where there is no increase or decrease in condensation or frost generated on the mirror surface, and in the equilibrium state, the temperature sensor A mirror-cooled dew point meter provided with means for performing dew point temperature measurement control for measuring the temperature of the mirror surface detected by the above as a dew point temperature;
A humidity sensor that measures the humidity of the gas under measurement on a principle different from that of the specular cooling dew point meter,
The humidity measurement value obtained by converting the dew point temperature measured by the specular cooling dew point meter is the first humidity measurement value, the humidity measurement value measured by the humidity sensor is the second humidity measurement value, A humidity measurement system that selects one of the first and second humidity measurement values as an effective humidity measurement value and outputs the selected humidity measurement value as an official humidity measurement value of the gas to be measured,
Reliability determination means for determining the reliability of the first humidity measurement value;
When the reliability of the first humidity measurement value is affirmed by the reliability determination unit, the first humidity measurement value is selected as an effective humidity measurement value to obtain a normal humidity measurement value at normal time. When the reliability of the first humidity measurement value is denied by the reliability determination means, the second humidity measurement value is selected as an effective humidity measurement value to be an official humidity measurement value at the time of abnormality. A humidity measurement system comprising: a humidity measurement value selection means. In the humidity measurement system according to claim 1,
The reliability determination means includes
The humidity measurement system characterized by determining the reliability of the first humidity measurement value based on the difference between the first humidity measurement value and the second humidity measurement value. In the dew point temperature measurement system according to claim 1,
The reliability determination means includes
Humidity characterized by periodically interrupting dew point temperature measurement control of the specular cooling dew point meter and determining the reliability of the first humidity measurement value based on the amount of reflected light received by the light receiving means. Measuring system. In the humidity measurement system according to claim 3,
The reliability determination means includes
When determining the reliability of the first humidity measurement value by periodically interrupting the dew point temperature measurement control of the mirror-cooled dew point meter,
After the interruption of the control of the current supplied to the thermoelectric cooling element by the dew point temperature measurement control, the amount of the reflected light is determined in advance based on the amount of the reflected light received by the light receiving means after a predetermined time has elapsed since the interruption. A humidity measurement system, wherein the reliability of the first humidity measurement value is denied when the received light amount is out of the reference range. In the humidity measurement system according to claim 3,
The reliability determination means includes
When determining the reliability of the first humidity measurement value by periodically interrupting the dew point temperature measurement control of the mirror-cooled dew point meter,
After interruption of control of the current supplied to the thermoelectric cooling element by the dew point temperature measurement control, the reflected light is based on the amount of reflected light received by the light receiving means when it is determined that the temperature of the mirror surface no longer changes. The humidity measurement system, wherein the reliability of the first humidity measurement value is denied when the amount of light deviates from a predetermined light reception amount reference range. In the humidity measurement system according to claim 3,
The reliability determination means includes
When determining the reliability of the first humidity measurement value by periodically interrupting the dew point temperature measurement control of the mirror-cooled dew point meter,
The amount of reflected light received by the light receiving means when it is determined that there is no change in the amount of reflected light received by the light receiving means after interruption of control of the current supplied to the thermoelectric cooling element by the dew point temperature measurement control The humidity measurement system is characterized in that the reliability of the first humidity measurement value is denied when the amount of reflected light deviates from a predetermined received light amount reference range. In the humidity measurement system described in any one of Claims 1-6,
The control means of the specular cooling dew point meter is:
Automatic cleaning that would be attached to the mirror surface , usually a gas, contained in the gas to be measured, becomes a solid at a temperature lower than the dew point temperature, and removes condensed substances that contaminate the mirror surface by evaporation or sublimation Means for performing the control,
The mirror-cooled dew point meter is
The dew point temperature measurement control is always executed, and when the reliability of the first humidity measurement value is denied by the reliability determination unit, the dew point temperature measurement control is stopped and the process proceeds to the automatic cleaning control. Humidity measurement system characterized by In the humidity measurement system according to claim 7,
The mirror-cooled dew point meter is
As the automatic cleaning control,
In order to remove the condensed substances that would be attached to the mirror surface , usually contained in the gas under measurement, become solid at a temperature lower than the dew point temperature, and condense the mirror surface by evaporation or sublimation , A humidity measurement system, wherein a current supplied to the thermoelectric cooling element is controlled so as to increase a temperature of the mirror surface. In the humidity measurement system according to claim 7,
The mirror-cooled dew point meter is
At least a chamber for accommodating the mirror surface, the thermoelectric cooling element, the temperature sensor, the light projecting means, and the light receiving means;
As the automatic cleaning control,
In order to remove the condensed substances that would be attached to the mirror surface , usually contained in the gas under measurement, become solid at a temperature lower than the dew point temperature, and condense the mirror surface by evaporation or sublimation , A humidity measurement system, wherein the pressure in the chamber is reduced.

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