JP5643599B2 - Mirror surface cooling type sensor - Google Patents

Description

  The present invention relates to a mirror-cooled sensor that detects condensation or frost formed on a mirror surface that is cooled by using a thermoelectric cooling element in which one surface is a low temperature side and the other surface is a high temperature side.

  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, when a mirror is cooled using a cryogen, a refrigerator, an electronic cooler, etc., a change in the intensity of reflected light on the mirror surface of the cooled mirror is detected, and the intensity of the reflected light is in an equilibrium state A mirror-cooled dew point meter is used to detect the dew point of moisture in the gas to be measured by measuring the temperature of the mirror surface.

  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. 17 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, 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. In this case, the supply current to the thermoelectric cooling element 2 is controlled to be in an equilibrium state where there is no increase / decrease in the condensation occurring on the mirror surface 3-1.

(Scattered light detection method)
FIG. 18 shows a configuration of a sensor unit in a conventional mirror-cooled dew point meter employing 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. In this case, the supply current to the thermoelectric cooling element 2 is controlled to be in an equilibrium state where there is no increase / decrease in the condensation occurring on the mirror surface 3-1.

  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.

JP-A-61-75235 Japanese Patent Publication No. 07-104304

  However, in the conventional mirror-cooled dew point meter described above, the same control that achieves both responsiveness and stability at the dew point and the frost point as control parameters when controlling condensation or frost on the mirror surface to an equilibrium state. The parameter was used. For this reason, there is a problem that when the dew point is detected, the response is slow, and when the frost point is detected, hunting is likely to occur.

  Although it is conceivable that the user adjusts the control parameter according to the dew point and the frost point, the user has to grasp the state on the mirror surface and manually adjust the control parameter, which is very troublesome.

  The present invention has been made to solve such a problem, and the purpose of the present invention is to detect a dew point and a frost point without the user grasping the state on the mirror surface. Thus, an object of the present invention is to provide a mirror-cooled sensor capable of automatically switching to an appropriate control parameter.

In order to achieve such an object, a mirror-cooled sensor according to the present invention includes a mirror surface exposed to a gas to be measured, a thermoelectric cooling element that cools the mirror surface, a temperature detection unit that detects the temperature of the mirror surface, Produced on the mirror surface based on the light projecting means for irradiating the mirror surface with light, the light receiving means for receiving the reflected light of the light irradiated from the light projecting means to the mirror surface, and the amount of reflected light received by the light receiving means And control means for controlling the current supplied to the thermoelectric cooling element so as to achieve an equilibrium state in which there is no increase or decrease in dew condensation or frost formation, and the control means sets the specular temperature region to the first temperature according to the specular state. The current mirror surface temperature detected by the temperature detecting means is divided into two regions, a region and a second temperature region which is a lower temperature region than the first temperature region, and the first temperature region and the second temperature. Specular temperature region to determine which region is Performing a constant section, by mirror temperature region judging means, the current mirror temperature control if it is determined that the first temperature region current supplied to the thermoelectric cooling element using the first control parameter On the other hand, when it is determined that the current mirror surface temperature is in the second temperature range, a control parameter switching unit that controls the current supplied to the thermoelectric cooling element using the second control parameter is provided. Features.

In the present invention, the control parameter switching means supplies to the thermoelectric cooling element using the first control parameter when the specular temperature region determining means determines that the current mirror surface temperature is in the first temperature region. On the other hand, when it is determined that the current mirror surface temperature is in the second temperature range, the current supplied to the thermoelectric cooling element is controlled using the second control parameter.

For example, as an example, when the mirror surface temperature region is divided into two temperature regions, and the current mirror surface temperature is in the first temperature region (for example, when the mirror surface temperature ≧ −5 ° C.), the first control parameter Is used to control the current supplied to the thermoelectric cooling element, and the second control parameter is used when the current mirror surface temperature is in the second temperature range (for example, when the mirror surface temperature <−5 ° C.). Thus, the current supplied to the thermoelectric cooling element is controlled.

  For example, as another example, the first control parameter is determined when it is determined by the frost determination means whether or not the mirror surface is in a state where frost is generated. Is used to control the current supplied to the thermoelectric cooling element. On the other hand, if it is determined that frost formation has occurred, the second control parameter is used to control the current supplied to the thermoelectric cooling element. .

According to the present invention, according to the state of the mirror surface, according to the present invention, the mirror temperature region is divided into two regions, a first temperature region and a second temperature region that is a lower temperature region than the first temperature region. split, and the specular temperature region determining means for determining whether the current mirror temperature is in any of the first temperature region and second temperature region, by mirror temperature region judging means, the current mirror temperature first temperature When the current mirror surface temperature is determined to be in the second temperature region while the current supplied to the thermoelectric cooling element is controlled using the first control parameter when determined to be in the region. Is provided with control parameter switching means for controlling the current supplied to the thermoelectric cooling element using the second control parameter, so that the user can detect the dew point without knowing the state on the mirror surface and frost Appropriate control is automatically applied when detecting points. It is possible to perform the switching to the parameter.

1 is a schematic configuration diagram of a mirror-cooled dew point meter showing an embodiment of a mirror-cooled sensor according to the present invention. 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 the operation | movement at the time of the subcooler starting by the main controller side in this mirror surface cooling-type dew point meter. It is a flowchart which shows the operation | movement of the abnormality monitoring performed regularly by the main controller side in this specular cooling type dew point meter. It is a flowchart which shows the normal / abnormal judgment operation | movement of the state of a mirror surface at the time of dew point measurement ON / OFF switch OFF by the main controller side in this mirror surface cooling-type dew point meter. It is a flowchart which shows the normal / abnormal judgment operation of the mirror surface state on the main controller side when the mirror surface state dew point meter is provided with a mirror surface state confirmation switch. It is a flowchart which shows the modification of the determination operation | movement of normal / abnormal of the state of a mirror surface by the main controller side at the time of providing the confirmation switch of a mirror surface state in this mirror surface type dew point meter. 7 is a flowchart showing an operation on the main controller side when the mirror surface state is normally / abnormally determined in this mirror-cooled dew point meter. 7 is a flowchart showing an operation on the main controller side 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 by the side of the main controller at the time of switching a control parameter based on the relationship between mirror surface temperature and a reference | standard dew point in this mirror surface cooling type dew point meter. In this mirror-cooled dew point meter, when the mirror surface temperature is divided into two temperature regions, the high dew point region and the low dew point region with the reference dew point as the boundary, the change from the high dew point region to the low dew point region and the low dew point region are switched. Figure showing the response of the mirror surface temperature to the change from the dew point region to the high dew point region in comparison with the response when using only the control parameter for the high dew point region and the control parameter for the low dew point region. It is. It is a schematic block diagram of the mirror surface cooling type dew point meter which shows the example which provided the camera which images the state of a mirror surface in this mirror surface cooling type dew point meter. It is a flowchart which shows the operation | movement by the side of the main controller at the time of switching a control parameter based on the image information of the camera which images the state of a mirror surface. It is a figure which shows the example which attached the sensor part to the sampling chamber so that the detection part may be located in the sampling chamber. 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.
FIG. 1 is a schematic configuration diagram of a mirror-cooled dew point meter showing an embodiment of a mirror-cooled sensor according to the present invention. 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 15 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 the present embodiment, 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 from the comparison of the sizes. .

  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 the present embodiment, 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 an auxiliary cooler (subcooler), but the main configuration of the auxiliary cooler (subcooler) 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 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 display unit 24-4, a RAM 24-5, and a ROM 24- 6 is provided. 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 display program as a program unique to the present embodiment.

  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 display unit 24-4 and the CPU 24-1. The display unit 24-4 displays the mirror surface temperature tPpv converted into a digital signal from the first temperature sensor 12.

  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 as a program unique to the present embodiment.

  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.

[Attaching the sensor to the duct]
In this mirror-cooled dew point meter 201, for example, when detecting the dew point of moisture in the gas to be measured flowing in the duct, the first thermoelectric cooling element 2, the mirror surface 11-1, the light-projecting optical fiber 14-1, The sensor unit 201A is attached to the duct so that the detection unit DT including the optical fiber 14-2 on the light receiving side is positioned in the gas to be measured. At this time, the subcooler SC including the second thermoelectric cooling element 18 is positioned outside the duct.

[Sub-cooler low temperature / high temperature / linked switching setting]
In the present embodiment, whether the subcooler SC is operated at “low temperature (for example, fixed at −5 ° C.)” or “high temperature (for example, fixed at 25 ° C.)” or “interlocked (mirror surface temperature + α)”. It is possible to selectively set the operation mode by using the subcooler low temperature / high temperature / interlocking selector switch 30.

[Dew point measurement with the operation mode set to "low temperature"]
Now, in a state where the sensor unit 201A is attached to the duct, 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. 2: YES in step S101), it starts the operation of the cooling fan 20 ( Step S102, signal S5). The operation of the cooling fan 20 may be started when the power switch 27 is turned on.

  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 S103). 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 S107 through step 106, 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 S112, 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 S113, 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. 3A). 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 that has occurred on the mirror surface 11-1 has reached an equilibrium state (dew point temperature) is displayed on the display unit 24-4 as the dew point temperature.

  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. 4 shows a cooling curve of the subcooler SC as a characteristic I, and 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 the present embodiment, by using the subcooler SC, a small element (Peltier with a high cooling speed) having a relatively small cooling capacity can be used as the first thermoelectric cooling element 2. 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, the case where the subcooler low temperature / high temperature / interlocking selector switch 30 is set to “interlocking” and the dew point measurement is started in a state where the sensor unit 201A is attached to the duct 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. 2: YES in step S101), it starts the operation of the cooling fan 20 ( Step S102).

  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 S103). In this case, since the setting state of the sub-cooler low temperature / high temperature / interlocking selector switch 30 is “interlocking”, the mirror surface temperature tPpv from the first temperature sensor 12 is acquired (step S104), and the sub-cooler setting target temperature is obtained. Tsp is set to a mirror surface temperature tPpv + α (step S105).

  Then, the outside air temperature tout from the outside air temperature sensor 23 is taken in (step S109), and the set target temperature Tsp determined in step S105 is compared with the outside air temperature tout (step S110). If the set target temperature Tsp is equal to or lower than the outside air temperature tout (YES in step S110), the subcooler temperature tSpv from the second temperature sensor 21 is taken in (step S112), and the subcooler 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 S113).

  On the other hand, when the set target temperature Tsp is higher than the outside air temperature tout (NO in step S110), the set target temperature Tsp is set as the outside air temperature tout (step S111), that is, the upper limit value of the set target temperature Tsp is set as the outside air temperature. The current supplied to the second thermoelectric cooling element 18 is ON / OFF controlled so that the subcooler temperature tSpv and the set target temperature Tsp coincide with each other (steps S112 and S113).

[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, when the subcooler low temperature / high temperature / linkage selector switch 30 is set to “linkage”, that is, when 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. 2: Steps S106 and S108).

  Then, the subcooler temperature tSpv from the second temperature sensor 21 is taken in (step S112), 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 (step S113). 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 the present embodiment, 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 present embodiment, since the main controller 24 requires high-speed control and high-precision measurement, a high-performance and high-price controller is used, and the sub-controller 25 does not require much control performance and measurement accuracy. 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.

  Further, in the present embodiment, the second A / D converter 24-3 and the display unit 24-4 are provided in the main controller 24, but the second A / D converter 24-3 and the display unit 24 are provided. -4 may be provided separately from the main controller 24. It is also conceivable that the mirror surface temperature tPpv is sent to the host device and displayed on the display unit of the host device.

  In the present embodiment, the control cycle of the supply current from the main controller 24 to the first thermoelectric cooling element 2 is shorter than the control cycle of the supply current from the sub-controller 25 to the second thermoelectric cooling element 18. 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 ON / You may make it be 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.

[Start / stop of the sub-controller via the main controller]
Next, the operation of the main controller 24 when starting / stopping the sub controller 25 via the main controller 24 will be described.

[(1) Input / output check of photoelectric converter]
When the sub cooler control ON / OFF switch 29 is turned on (FIG. 5: YES in step S201), the CPU 24-1 of the main controller 24 performs input / output check of the photoelectric converter 22 (step S202). That is, the level of the signal S4 from the photoelectric converter 22 is checked as an input from the photoelectric converter 22, and the level of the signal S3 from the CPU 24-1 to the photoelectric converter 22 is checked as an output to the photoelectric converter 22. .

  Here, the level of the signal S4 from the photoelectric converter 22 is not in the normal range, the level of the signal S3 to the photoelectric converter 22 is not in the normal range, or the signal S3 (S4) with respect to the level of the signal S4 (S3). If the level is outside the predicted range, it is determined that there is an abnormality (YES in step S203).

  In this example, the input / output check of the photoelectric converter 22 is performed. However, only the input check of the photoelectric converter 22 may be performed, or only the output check of the photoelectric converter 22 may be performed. Also good.

[(2) Checking control output]
If the input / output of the photoelectric converter 22 is normal (NO in step S203), the CPU 24-1 checks the control output (step S204). That is, as the control output from the main controller 24, the level of the signal S1 to the first thermoelectric cooling element 2 is checked. Here, if the level of the signal S1 to the first thermoelectric cooling element 2 is not within the normal range, it is determined that there is an abnormality (YES in step S205).

[(3) Temperature sensor input check]
If the control output from the main controller 24 is normal (NO in step S205), the CPU 24-1 checks the temperature sensor input (step S206). That is, the level of the signal S2 from the first temperature sensor 12 is checked as a temperature sensor input. Here, when the level of the signal S2 from the first temperature sensor 12 is not in the normal range, it is determined that there is an abnormality (YES in step S207).

[(4) Main controller self-check]
If the temperature sensor input is normal (NO in step S207), the CPU 24-1 performs a self-check of the main controller 24 (step S208). That is, for the main controller 24, various predetermined parameters are checked. Here, if there is even one problem, it is determined that there is an abnormality (YES in step S209).

[(5) Check for connection between sub-controller and cooling fan]
If the self-check of the main controller is normal (NO in step S209), the CPU 24-1 checks whether or not there is a connection between the sub controller and the cooling fan (step S210). That is, it is checked whether or not the signal S5 line from the sub-controller 25 to the cooling fan 20 is actually connected.

  In the present embodiment, by design, the signal S5 line from the sub-controller 25 to the cooling fan 20 is accommodated in the relay cable J1 together with the signals S1 to S4, and the signal S6 and S7 lines are accommodated in the relay cable J2. ing. For this reason, if the sub-controller 25 is started without connecting the relay cable J1 to the sensor unit 201, the cooling operation of the second thermoelectric cooling element 18 starts, but the cooling fan 20 does not rotate. Therefore, it is checked whether or not the signal S5 line from the sub-controller 25 to the cooling fan 20 is actually connected, and if it is not connected, it is determined that there is an abnormality (YES in step S211).

  It should be noted that the presence or absence of signal S5 line connection from the sub-controller 25 to the cooling fan 20 is checked from, for example, the pin P1 that is short-circuited with the signal S3 line when the relay cable J1 is connected to the sensor unit 201A. The return signal S9 is determined as a connection check signal in the CPU 24-1.

  If the check of the connection between the sub-controller and the cooling fan is normal (NO in step S211), the CPU 24-1 notifies the sub-controller 25 that the sub-cooler control ON / OFF switch 29 is turned on. To the CPU 25-1 to activate the sub-controller 25 (step S212).

  If the CPU 24-1 determines that any one of steps S203, S205, S207, S209, and S211 is abnormal, the sub controller 25 is not started (step S213), that is, the sub controller 25 is prevented from starting. Then, an alarm is displayed on the display unit 24-4 (step S214).

  Further, when the sub-cooler control ON / OFF switch 29 is turned off during the operation of the sub-controller 25 (YES in step S215), the CPU 24-1 notifies that the sub-cooler control ON / OFF switch 29 is turned off. It is unconditionally sent to the CPU 25-1 of the sub controller 25, and the sub controller 25 is stopped (step S216).

[Abnormality monitoring]
The CPU 24-1 of the main controller 24 performs the above-described “(1) photoelectric converter input / output check”, “(2) control output check”, “(3) temperature” as an abnormality monitor during the operation of the sub-controller 25. The “sensor input check”, “(4) self-check of main controller”, and “(5) check for connection between sub-controller and cooling fan” are repeated periodically. FIG. 6 shows a flowchart in this case. The processing of this flowchart is repeatedly performed by interruption processing.

  In this abnormality monitoring, if any one of the CPUs 24-1 is determined to be abnormal, that is, if any one of steps S302, S304, S306, S308, and S310 is determined to be abnormal, the operation of the sub-controller 25 is changed. After stopping (step S311), an alarm is displayed on the display unit 24-4 (step S312).

  In the flowcharts shown in FIGS. 5 and 6, “(1) photoelectric converter input / output check”, “(2) control output check”, “(3) temperature sensor input check”, (4) "Main controller self-check" and "(5) Check for connection between sub-controller and cooling fan" are checked in order, but the order of checking is free. Any one of the abnormality check items may be performed. Also, the abnormality check items are not limited to these. Further, when the abnormality is recovered, the operation of the sub-controller 25 that has been stopped may be automatically restored.

[Normal / abnormal judgment of mirror surface status using the received light intensity reference range]
When the dew point measurement ON / OFF switch 28 is turned off (FIG. 7: YES in step S401), the CPU 24-1 of the main controller 24 interrupts the control of the supply current to the first thermoelectric cooling element 2, and the dew point is determined. Measurement is stopped (step S402).

  Then, after the elapse of a predetermined time (YES in step S403), a 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 S404). ).

  Then, it is checked whether or not the calculated received light amount Rpv is within a predetermined received light amount reference range (step S405). If the received light amount Rpv is out of the received light amount reference range (NO in step S405). ), An alarm is displayed on the display unit 24-4 (step S406).

  That is, after interrupting the control of the current supplied to the first thermoelectric cooling element 2 (step S402), the CPU 24-1 waits for the elapse of a predetermined time (step S403), thereby causing condensation on the mirror surface 11-1. A light reception amount Rpv of the reflected light from the mirror surface 11-1 at this time is obtained (step S404), and if the light reception amount Rpv is not within the light reception amount reference range that is recognized as normal (step S405) NO), it is determined that an abnormality such as dirt on the mirror surface or deterioration of the detection system has occurred, and an alarm is issued (step S406). In the present embodiment, the abnormal state of the mirror surface includes deterioration of the detection system in addition to the contamination of the mirror surface.

  In this example, the case where the dew point measurement ON / OFF switch 28 is turned off has been described. However, when the mirror surface state confirmation switch is provided independently, and the mirror surface state confirmation switch is turned on, the mirror surface is turned on. Whether the state is normal or abnormal may be determined.

  FIG. 8 shows a flowchart in the case where a mirror state confirmation switch is provided. When a mirror surface state confirmation switch (not shown) is turned on (YES in step S501), the CPU 24-1 of the main controller 24 interrupts the control of the supply current to the first thermoelectric cooling element 2, and the dew point Measurement is paused (step S502).

  Then, after the elapse of a predetermined time (YES in step S503), 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 S504). ).

  If the calculated received light amount Rpv is out of the received light amount reference range (NO in step S505), an alarm is displayed (step S506), and dew point measurement is stopped (step S507).

  When the received light amount Rpv is within the received light amount reference range (YES in step S505), the CPU 24-1 cancels the interruption of the control of the current supplied to the first thermoelectric cooling element 2 and restarts dew point measurement ( Step S508).

  As shown in FIG. 9, when the received light amount Rpv is out of the received light amount reference range (NO in step S505), while displaying an alarm (step S506), dew point measurement may be resumed (step S506). Step S508).

  Further, during the confirmation of the mirror surface state, the operation of the subcooler SC may be stopped. In this example, in order to minimize the check time, the operation of the subcooler SC is continued during the confirmation of the mirror surface state. To do.

  Further, as shown in FIG. 10, as the periodic interrupt processing operation of the CPU 24-1 of the main controller 24, the processing operations in steps S601 to S607 corresponding to steps S502 to S508 shown in FIG. 8 are repeated. Also good. Also in this case, after the alarm is displayed in step S605, the process proceeds to step S607 as indicated by the dotted line in the figure, and dew point measurement may be resumed.

  Further, in the flowcharts shown in FIGS. 7 to 10, after the control of the current supplied to the first thermoelectric cooling element 2 is interrupted, the received light amount Rpv of the reflected light from the mirror surface 11-1 after a predetermined time has elapsed is obtained. However, after the control of the current supplied 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, and the change in the mirror surface temperature tPpv no longer occurs The amount of received light Rpv of the reflected light from the mirror surface 11-1 may be obtained.

  FIG. 11 illustrates a flowchart in this case. This flowchart is a flowchart corresponding to FIG. 10. In step S602-1, the change in the mirror surface temperature tPpv is checked, and in step S 602-2, it is determined when the mirror surface temperature tPpv no longer changes. 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.

[Detection of frost point]
In the embodiment described above, the condensation (dew point) generated on the mirror surface 11-1 is detected, but the frost (frost point) generated on the mirror surface 11-1 can also be detected by the same configuration. 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 can also be detected.

[Switching of control parameters between the high dew point area and the low dew point area]
In the present embodiment, the RAM 24-5 of the main controller 24 stores a first control parameter and a second control parameter, respectively. The first control parameter is predetermined as an appropriate control parameter for the high dew point region, and the second control parameter is predetermined as an appropriate control parameter for the low dew point region. The high dew point region refers to a region where the mirror surface temperature is high with a preset reference dew point as a boundary, and the low dew point region refers to a region where the mirror surface temperature is low with respect to a preset reference dew point. In this case, the reference dew point is preferably set between the dew point and the frost point.

  In this embodiment, the first control parameter and the second control parameter are both PID parameters configured by a proportional gain (P parameter), an integration time (I parameter), and a differentiation time (D parameter). Yes. The proportional gain in the first control parameter is set higher than the proportional gain in the second control parameter, and the integration time in the first control parameter is set shorter than the integration time in the second control parameter.

  Note that the differential time is the same in the first control parameter and the second control parameter. Further, in the first control parameter and the second control parameter, the proportional gain and the integration time in both parameters are set so that the product (P × I) of the proportional gain and the integration time is equal between the two parameters. ing.

  The CPU 24-1 of the main controller 24 checks the relationship between the mirror surface temperature tPpv from the first temperature sensor 12 and the reference dew point (FIG. 12: step S701), and the mirror surface temperature tPpv is equal to or higher than the reference dew point (for example, −5 ° C.). If so (YES in step S701), the control parameter for the high dew point region is selected (step S702), and the supply current to the first thermoelectric cooling element 2 is controlled (step S704).

  On the other hand, if the mirror surface temperature tPpv is below the reference dew point (−5 ° C.) (NO in step S701), the CPU 24-1 of the main controller 24 selects a control parameter for the low dew point region (step S703). Then, the supply current to the first thermoelectric cooling element 2 is controlled (step S704).

  That is, the CPU 24-1 of the main controller 24 divides the temperature region of the mirror surface 11-1 into two temperature regions with a boundary of −5 ° C. set as the reference dew point, and the mirror surface temperature tPpv is equal to or higher than the reference dew point −5 ° C. If it is in the region (first temperature region), the control of the supply current to the first thermoelectric cooling element 2 is performed using the control parameter (first control parameter) for the high dew point region. Further, if the mirror surface temperature tPpv is in a region (second temperature region) lower than the reference dew point −5 ° C., the first thermoelectric cooling element is used by using the control parameter for the low dew point region (second control parameter). The supply current to 2 is controlled.

  FIG. 13 (a) shows the response of the mirror surface temperature to the change from the high dew point region to the low dew point region and the change from the low dew point region to the high dew point region when the control parameter is switched at the reference dew point of −5 ° C. Showing gender. In the figure, a characteristic A indicated by a solid line is an ideal response, and a characteristic B indicated by a dotted line is a response when the control parameter is switched at a reference dew point of −5 ° C. When the mirror surface state changes from dew condensation to frost at the point t1 shown in the figure, the mirror surface temperature also changes to follow this. When the mirror surface state changes from the frost point to the dew point at the point t2 in the figure, the mirror surface temperature also changes from the dew point to the frost point so as to follow this.

  FIG. 13B shows the case where only the control parameter for the high dew point region is used, and FIG. 13C shows the case where only the control parameter for the low dew point region is used. If only the control parameters for the high dew point area are used, the mirror surface temperature will be hunted when the mirror surface state changes from dew condensation to frost, that is, when the dew point temperature moves to the low dew point area. The response is slow. On the other hand, if only the control parameters for the low dew point area are used, the mirror surface temperature will be hunting and stable when the mirror surface state changes from frost to dew condensation, that is, when the dew point temperature moves to the high dew point area. The response is poor and the response is slow. On the other hand, by switching and using the control parameter for the high dew point region and the control parameter for the low dew point region, as shown in FIG. 13A, stability is good even when the mirror surface state is dew condensation, Responsiveness also becomes faster.

  In this example, the control parameter is switched with a reference dew point of −5 ° C. as a boundary. However, the reference dew point as a boundary is not necessarily limited to −5 ° C. The reference dew point that divides the specular temperature region into the high dew point region (first temperature region) and the low dew point region (second temperature region) may be provided with hysteresis depending on the direction of change in the specular temperature. . For example, when the mirror surface temperature is changing in the decreasing direction, −5 ° C. is set as the boundary temperature for switching the control parameter using the reference dew point, and when the mirror surface temperature is changing in the increasing direction, −3 Use ℃ as the standard dew point and the boundary temperature for switching control parameters.

  Further, as shown in FIG. 14, a camera 33 that captures the state of the mirror surface 11-1 is provided, and image information captured by the camera 33 is sent to the CPU 24-1 of the main controller 24. You may make it discriminate | determine whether the state of the mirror surface 11-1 is the state in which the frost has arisen (FIG. 15: step S801).

  In this case, the state in which frost is formed includes a state in which frost starts to be generated. If the frost is not generated (“state other than frost” in step S801), the main controller 24 The CPU 24-1 determines that the current mirror surface temperature is in the first temperature range, selects a dew point detection control parameter (first control parameter) (step S802), and the first thermoelectric cooling element 2 The supply current is controlled (step S804).

  On the other hand, if frost is formed ("frost state" in step S801), the CPU 24-1 of the main controller 24 determines that the current mirror surface temperature is in the second temperature range. Then, the control parameter (second control parameter) for detecting the frost point is selected (step S803), and the supply current to the first thermoelectric cooling element 2 is controlled (step S804).

  That is, the CPU 24-1 of the main controller 24 determines whether or not the state of the mirror surface 11-1 is a state where frost is formed from the image information captured by the camera 33, and determines that the state is free of frost. In this case, it is assumed that the mirror surface temperature is in the first temperature region, and the control of the supply current to the first thermoelectric cooling element 2 is performed using the dew point detection control parameter (first control parameter). When it is determined that frost formation has occurred, it is assumed that the mirror surface temperature is in the second temperature range, and the control parameter for detecting frost point (second control parameter) is used to The supply current to the thermoelectric cooling element 2 is controlled. Accordingly, it is possible to automatically switch to an appropriate control parameter depending on whether the user detects the dew point or the frost point without grasping the state on the mirror surface.

  In the embodiment described above, the dew point measurement ON / OFF switch 28 and the subcooler control ON / OFF switch 29 are provided separately, but the dew point measurement ON / OFF switch 28 and the subcooler control ON / OFF switch 29 are provided separately. May be configured by one 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.

  In the above-described embodiment, the first thermoelectric cooling element 2 is a single-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.

  In the above-described embodiment, the sensor unit 201A is attached to the duct. However, as shown in FIG. 16, the sampling chamber is positioned so that the detection unit DT is positioned in the sampling chamber 31 into which the gas to be measured is drawn. The sensor unit 201 </ b> A may be attached to 31 via the heat insulating material 32.

  In the embodiment described above, the second thermoelectric cooling element 18 is provided. However, the second thermoelectric cooling element 18 is not necessarily provided, and only the first thermoelectric cooling element 2 is provided. It does not matter.

  The mirror surface cooling type sensor of the present invention can be used as a mirror surface cooling type sensor using a thermoelectric cooling element (Peltier element) for a dew point meter for detecting condensation or frost generated on the mirror surface of the mirror.

  DESCRIPTION OF SYMBOLS 201 ... Mirror surface cooling type dew point meter, 201A ... Sensor part, 201B ... Control part, 2 ... 1st 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 ... 1st 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 ... first A / D converter, 24-3 ... second A / D converter, 24-4 ... display unit, 24-5 ... RAM, 24- 6 ... ROM, 25 ... sub-controller, 25-1 ... CPU, 25-2 ... first A / D converter, 25-3 ... second A / D converter, 25-4 ... RAM, 25-5 ... ROM, 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, J1, J2 ... relay cable, P1 ... Pin, 31 ... Sampling chamber, 32 ... Heat insulation, 33 ... Camera.

Claims (6)

A mirror surface exposed to the gas to be measured;
A thermoelectric cooling element for cooling the mirror surface;
Temperature detecting means 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 so as to be in an equilibrium state where there is no increase or decrease in condensation or frost generated on the mirror surface based on the amount of reflected light received by the light receiving means,
The control means includes
According to the state of the mirror surface, the region of the mirror surface temperature is divided into a first temperature region and a second temperature region that is a lower temperature region than the first temperature region, and the temperature detecting means detects and the current mirror temperature that is mirror-temperature region determination means for determining one of whether there the first temperature region and second temperature region,
When the current mirror surface temperature is determined to be in the first temperature region by the mirror surface temperature region determining means, the current supplied to the thermoelectric cooling element is controlled using the first control parameter, Control parameter switching means for controlling the current supplied to the thermoelectric cooling element using the second control parameter when it is determined that the current mirror surface temperature is in the second temperature region. Mirror surface cooling type sensor. The mirror-cooled sensor according to claim 1,
The specular temperature region determining means includes
A region having a high mirror surface temperature with a reference dew point set in advance as the first temperature region, and a region having a low mirror surface temperature with the reference dew point set in advance as the second temperature region, A mirror-cooled sensor that determines whether the current mirror surface temperature is in a first temperature region or a second temperature region. The mirror-cooled sensor according to claim 1,
Comprising frost determination means for determining whether or not the state of the mirror surface is a state where frost is generated;
The specular temperature region determining means includes
When the frost determination means determines that frost is not generated, the current mirror surface temperature is determined to be in the first temperature range, while the frost determination means is frost formed. If it is determined that the current mirror surface temperature is in the second temperature range, the mirror surface cooling type sensor. In the mirror surface cooling type sensor as described in any one of Claims 1-3,
The first control parameter and the second control parameter both include a proportional gain,
The mirror-cooled sensor, wherein the proportional gain of the first control parameter is higher than the proportional gain of the second control parameter. In the mirror surface cooling type sensor as described in any one of Claims 1-3,
Both the first control parameter and the second control parameter include an integration time;
The integration cooling time of the first control parameter is shorter than the integration time of the second control parameter. The mirror-cooled sensor according to claim 2,
The specular cooling type sensor, wherein a reference dew point that divides the specular temperature region into the first temperature region and the second temperature region is provided with a hysteresis depending on a change direction of the specular temperature.

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