JP4005581B2 - Mirror surface dew point meter - Google Patents

Description

The present invention relates to a mirror-cooled dew point meter that detects the dew point by cooling the mirror surface of the mirror and measuring the temperature of the mirror when moisture is generated on the mirror surface of the mirror .

  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, in Non-Patent Document 1, a mirror is cooled using a cryogen, a refrigerator, an electronic cooler, or the like, a change in the intensity of reflected light on the mirror surface of the cooled mirror is detected, and the temperature of the mirror surface at this time is detected. A mirror-cooled dew point meter that detects the dew point of the moisture in the gas to be measured is described.

  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. 9 shows a main part of a conventional mirror-cooled dew point meter adopting a regular reflection light detection method. The specular cooling dew point meter 101 includes a chamber 1 into which a gas to be measured is introduced and a thermoelectric cooling element (Peltier element) 2 provided inside the chamber 1. Bolts 4 are attached to the cooling surface 2-1 of the thermoelectric cooling element 2 via copper blocks 3, and radiating fins 5 are attached to the heating surface 2-2 of the thermoelectric cooling element 2. An upper surface 4-1 of the bolt 4 attached to the copper block 3 is a mirror surface. A winding type resistance temperature detector (temperature detection element) 6 is embedded in a side portion of the copper block 3 (see FIG. 13). Further, on the upper portion of the chamber 1, a light emitting element 7 that irradiates light obliquely to the upper surface (mirror surface) 4-1 of the bolt 4, and light emitted from the light emitting element 7 to the mirror surface 4-1. A light receiving element 8 for receiving the specularly reflected light is provided. A heat insulating material 40 is provided around the thermoelectric cooling element 2.

  In this mirror-cooled dew point meter 101, the mirror surface 4-1 in the chamber 1 is exposed to the gas to be measured that flows into the chamber 1. If there is no condensation on the mirror surface 4-1, almost all of the light emitted from the light emitting element 7 is regularly reflected and received by the light receiving element 8. Therefore, when there is no condensation on the mirror surface 4-1, the intensity of the reflected light received by the light receiving element 8 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 gas to be measured condenses on the mirror surface 4-1, and the water molecules Part of the light emitted from the light emitting element 7 is absorbed or diffusely reflected. Thereby, the intensity of the reflected light (regular reflected light) received by the light receiving element 8 is reduced. By detecting the change in the specularly reflected light on the mirror surface 4-1, it is possible to know the change in the state on the mirror surface 4-1, that is, that moisture (water droplets) has adhered to the mirror surface 4-1. Further, by indirectly measuring the temperature of the mirror surface 4-1 at this time with the temperature detecting element 6, it is possible to know the dew point of moisture in the gas to be measured.

(Scattered light detection method)
FIG. 10 shows a main part of a conventional mirror-cooled dew point meter adopting the scattered light detection method. This mirror-cooled dew point meter 102 has substantially the same configuration as the mirror-cooled dew point meter 101 employing the specular reflection light detection method, but the mounting position of the light receiving element 8 is different. In this mirror-cooled dew point meter 102, the light receiving element 8 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 7 to the mirror surface 4-1. Yes.

  In this mirror-cooled dew point meter 102, the mirror surface 4-1 is exposed to the gas to be measured that flows into the chamber 1. If there is no condensation on the mirror surface 4-1, almost all of the light emitted from the light emitting element 7 is regularly reflected, and the amount of light received by the light receiving element 8 is extremely small. Therefore, when no condensation occurs on the mirror surface 4-1, the intensity of the reflected light received by the light receiving element 8 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 gas to be measured condenses on the mirror surface 4-1, and the water molecules Part of the light emitted from the light emitting element 7 is absorbed or diffusely reflected. Thereby, the intensity of the irregularly reflected light (scattered light) received by the light receiving element 8 increases. By detecting the change in the scattered light on the mirror surface 4-1, it is possible to know a change in the state on the mirror surface 4-1, that is, that moisture (water droplets) has adhered to the mirror surface 4-1. Further, by indirectly measuring the temperature of the mirror surface 4-1 at this time with the temperature detecting element 6, it is possible to know the dew point of moisture in the gas to be measured.

In addition, in the dew point meter mentioned above, it demonstrated by the example which detects the dew condensation (water | moisture content) which arises on the mirror surface 4-1, However, It is also possible to detect the frost (water | moisture content) which arises on the mirror surface 4-1 with the same structure. is there.
11 and FIG. 12, that is, the thermoelectric cooling element 2 and the temperature detecting element 6 are eliminated, only the mirror 9 is provided in the chamber 1, and the opening is provided on the upper surface of the chamber 1. Then, it can be used as an on-mirror state detection device (weather meter) that detects moisture adhering to the mirror surface 9-1 at the beginning of rain or snow. In the weather gauges 103 and 104, when rain or snow is drawn into the chamber 1 and adheres to the mirror surface 9-1 of the mirror 9, the adhesion is detected based on the intensity of reflected light received by the light receiving element 8. The

JP-A-61-75235 Japanese Examined Patent Publication No. 7-104304 Industrial Measurement Handbook, Showa 51.9.30, Asakura Shoten, P297.

  However, in the conventional mirror-cooled dew point meters 101 and 102 and the weather meters 103 and 104 described above, the chamber 1 is provided to prevent malfunction (shielding) due to ambient light, and the increase in size cannot be avoided. In particular, the mirror-cooled dew point meters 101 and 102 require a suction pump, a suction tube, an exhaust tube, a flow meter and the like for drawing the gas to be measured into the chamber 1, and have a large number of parts and poor assembly. There was a problem. In addition, the sensor portion is large, heavy, and inconvenient to carry.

The present invention has been made to solve such problems, and its object is to provide a mirror-cooled dew point meter with a small number of parts, a small size, good assembly, and convenient to carry. There is to do.

In order to achieve such an object, the mirror-cooled dew point meter of the present invention includes a mirror whose mirror surface is exposed to the gas to be measured, means for cooling the mirror, and pulse light is irradiated to the mirror surface at a predetermined cycle. On the mirror surface of the mirror cooled by the cooling means on the basis of the reflected light received by the light receiving means, the light receiving means for receiving the reflected light of the pulsed light emitted from the light emitting means to the mirror surface Difference between an upper limit value and a lower limit value for each pulse of reflected light received by the light receiving means in a mirror-cooled dew point meter having means for detecting moisture generated in the mirror and a temperature detecting element for detecting the temperature of the mirror And a means for detecting moisture generated on the mirror surface of the mirror cooled by the cooling means, and a chamber portion for blocking ambient light is not provided.
According to this invention, pulse light is emitted from the light emitting means to the mirror surface of the mirror at a predetermined period, and the reflected light from the mirror surface of the irradiated pulse light (regular reflection light in the case of the regular reflection light detection method), In the case of the scattered light detection method, scattered light) is received by the light receiving means, and based on the difference between the upper limit value and the lower limit value for each pulse of the reflected light (reflected pulse light) received by the light receiving means, the cooling means Moisture (for example, condensation or frost) generated on the mirror surface of the cooled mirror is detected. In this case, disturbance light included in the reflected light is removed by taking the difference between the upper limit value and the lower limit value of one pulse of the reflected light. Moreover, the chamber part for interrupting disturbance light becomes unnecessary.

According to the present invention, the light emitting means irradiates the mirror surface of the mirror with a predetermined cycle, the reflected light of the irradiated pulsed light from the mirror surface is received by the light receiving means, and the light receiving means receives the reflected light. Since the moisture generated on the mirror surface is detected based on the difference between the upper limit value and the lower limit value for each pulse of light (reflected pulsed light), disturbance light contained in the reflected light is removed without using a chamber. Thus, the number of parts can be reduced, the size can be reduced, the assemblability can be improved, and the carrying can be facilitated.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Embodiment 1: Mirror surface dew point meter (scattered light detection method)]
FIG. 1 is a schematic configuration diagram of a mirror-cooled dew point meter showing an embodiment of a mirror-cooled dew point meter according to the present invention. The mirror-cooled dew point meter 201 has a sensor unit 201A and a control unit 201B.

  In the sensor unit 201 </ b> A, the mirror 10 is attached to the cooling surface 2-1 of the thermoelectric cooling element (Peltier element) 2. The mirror 10 is a silicon chip, for example, and the surface 10-1 is a mirror surface. Further, a thin film resistance temperature detector (temperature detection element) 11 made of, for example, platinum is formed on the joint surface between the mirror 10 and the cooling surface 2-1 of the thermoelectric cooling element 2. Further, a cylindrical heat sink 18 is joined to the heating surface 2-2 of the thermoelectric cooling element 2, and a stainless steel tube 17 whose upper end is bent in a J shape along the heat sink 18 is provided.

  As the tube 17, a tube 16 containing optical fibers in various forms as shown in FIG. 2 can be used. In FIG. 2A, a light emitting side optical fiber 16-1 and a light receiving side optical fiber 16-2 are coaxially provided in a tube 16. In FIG. 2B, a light emitting side (or light receiving side) optical fiber 16-1 and a light receiving side (or light emitting side) optical fiber 16-21 to 16-24 are coaxially provided in a tube 16. In FIG. 2C, the left half of the tube 16 is the light-emitting side optical fiber 16a, and the right half is the light-receiving side optical fiber 16b. In FIG. 2D, the light emitting side optical fiber 16 c and the light receiving side optical fiber 16 d are mixed in the tube 16. In FIG. 2E, the central portion in the tube 16 is a light emitting side (or light receiving side) optical fiber 16e, and the periphery of the optical fiber 16e is a light receiving side (or light emitting side) optical fiber 16f.

  In the mirror-cooled dew point meter 201 shown in FIG. 1, the tube 16 of the type shown in FIG. 2A is used as the tube 17, and the light-emitting side optical fiber 17-1 and the light-receiving side of the tube 16 are contained therein. The optical fiber 17-2 is accommodated. The tip portions (light emitting portion and light receiving portion) of the light emitting side optical fiber 17-1 and the light receiving side optical fiber 17-2 which are curved in a J-shape are directed to the mirror surface 10-1 of the mirror 10, and this mirror surface 10 -1 with a predetermined inclination angle. As a result, the irradiation direction (optical axis) of the light from the optical fiber 17-1 and the light receiving direction (optical axis) of the light from the optical fiber 17-2 are made parallel, and the same inclination angle is set adjacently. The

  The control unit 201B is provided with a dew point temperature display unit 12, a dew condensation detection unit 13, a Peltier output control unit 14, and a signal conversion unit 15. The dew point temperature display unit 12 displays the temperature of the mirror 10 detected by the temperature detection element 11. The dew condensation detection unit 13 irradiates the mirror surface 10-1 of the mirror 10 with pulse light obliquely at a predetermined period from the tip of the optical fiber 17-1, and receives light reflected through the optical fiber 17-2. The difference between the upper limit value and the lower limit value of the pulsed light (scattered light) is obtained as the intensity of the reflected pulsed light, and a signal S 1 corresponding to the intensity of the reflected pulsed light is sent to the Peltier output control unit 14. The Peltier output control unit 14 receives the signal S1 from the dew condensation detection unit 13, compares the intensity of the reflected pulse light with a predetermined threshold value, and if the intensity of the reflected pulse light has not reached the threshold value. The control signal S2 for increasing the current to the thermoelectric cooling element 2 according to the value of the signal S1, and when the intensity of the reflected pulse light exceeds the threshold value, the current to the thermoelectric cooling element 2 is set to the value of the signal S1. The control signal S <b> 2 that decreases in response to the signal is output to the signal converter 15. The signal conversion unit 15 supplies the thermoelectric cooling element 2 with a current S3 indicated by the control signal S2 from the Peltier output control unit 14.

  In this mirror-cooled dew point meter 201, the sensor unit 201A is placed in the gas to be measured. Further, the dew condensation detector 13 irradiates the mirror surface 10-1 of the mirror 10 with pulsed light obliquely at a predetermined cycle from the tip of the optical fiber 17-1 (see FIG. 3A). If the mirror surface 10-1 is exposed to the gas to be measured and no condensation occurs on the mirror surface 10-1, almost all of the pulsed light irradiated from the tip of the optical fiber 17-1 is regularly reflected. The amount of reflected pulsed light (scattered light) from the mirror surface 10-1 received through the optical fiber 17-2 is extremely small. Accordingly, when no condensation occurs on the mirror surface 10-1, the intensity of the reflected pulse light received through the optical fiber 17-2 is small.

  In the dew condensation detection unit 13, the difference between the upper limit value and the lower limit value of the reflected pulse light received through the optical fiber 17-2 is obtained as the intensity of the reflected pulse light, and the signal S1 corresponding to the intensity of the reflected pulse light is obtained from the Peltier. This is sent to the output control unit 14. In this case, since the intensity of the reflected pulse light is almost zero and has not reached the threshold value, the Peltier output control unit 14 sends a control signal S2 for increasing the current to the thermoelectric cooling element 2 to the signal conversion unit 15. Thereby, the current S3 from the signal converter 15 to the thermoelectric cooling element 2 increases, and the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is lowered.

  When the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is lowered, that is, the temperature of the mirror 10, the water vapor contained in the gas to be measured is condensed on the mirror surface 10-1 of the mirror 10, and the water molecules are optical fiber. Part of the pulsed light irradiated from the tip portion of 17-1 is absorbed or irregularly reflected. Thereby, the intensity | strength of the reflected pulsed light (scattered light) from the mirror surface 10-1 light-received via the optical fiber 17-2 increases.

  The dew condensation detection unit 13 obtains the difference between the upper limit value and the lower limit value of each pulse of the received reflected pulse light, and uses this difference as the intensity of the reflected pulse light. That is, as shown in FIG. 3B, a difference ΔL between the upper limit value Lmax and the lower limit value Lmin of one pulse of the reflected pulse light is obtained, and this ΔL is used as the intensity of the reflected pulse light. By the process in the dew condensation detection unit 13, the disturbance light ΔX included in the reflected pulse light is removed, and malfunction due to the disturbance light is prevented. A processing method for preventing malfunction by disturbance light using pulsed light in the dew condensation detection unit 13 is referred to as a pulse modulation method. With this process, the mirror cooled dew point meter 201 can eliminate the chamber from the sensor unit 201A.

  Here, when the intensity of the reflected pulse light received through the optical fiber 17-2 exceeds the threshold value, the Peltier output control unit 14 transmits the control signal S2 for reducing the current to the thermoelectric cooling element 2 to the signal conversion unit 15. Send to. Thereby, the fall of the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is suppressed, and generation | occurrence | production of dew condensation is suppressed. By controlling the condensation, the intensity of the reflected pulse light received via the optical fiber 17-2 is reduced, and when the intensity falls below the threshold, the control signal S2 increases the current from the Peltier output control unit 14 to the thermoelectric cooling element 2. Is sent to the signal converter 15. By repeating this operation, the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is adjusted so that the intensity of the reflected pulse light received through the optical fiber 17-2 is approximately equal to the threshold value. The adjusted temperature, that is, the temperature at which the dew condensation that has occurred on the mirror surface 10-1 has reached an equilibrium state (dew point temperature) is displayed on the dew point temperature display unit 12 as the dew point temperature.

  In this mirror-cooled dew point meter 201, the attachment portions of the light-emitting side optical fiber 17-1 and the light-receiving side optical fiber 17-2 are gathered in one place, which contributes to the downsizing of the detection unit 201A. Further, since the light-emitting side optical fiber 17-1 and the light-receiving side optical fiber 17-2 are accommodated in the tube 17, the space between the light-emitting side optical fiber 17-1 and the light-receiving side optical fiber 17-2. There is no need for positioning at this point, and the workability during assembly is improved.

  Further, in this mirror-cooled dew point meter 201, the chamber is eliminated from the sensor unit 201A, and the suction pump, the suction tube, the exhaust tube, the flow meter, and the like can be omitted. Further downsizing of 201A is achieved, the assembling property is improved, and the cost is also reduced. Further, since it is not necessary to attach a suction pump, a suction tube, an exhaust tube, a flow meter, etc., installation in a measurement atmosphere is facilitated. The sensor unit 201A is not accompanied by a suction pump, a suction tube, an exhaust tube, a flow meter, or the like, and has two configurations of the sensor unit 201A and the control unit 201B.

  FIG. 4 shows the configuration of a mirror-cooled dew point meter 201 in which the control unit 201B is accommodated in the control box 21. In the control box 21, the power supply to the accommodated control unit 201B is a battery. By placing the control box 21 and the sensor unit 201A in one set and going to the site, the sensor unit 201A is installed in a measurement atmosphere. You can start measuring immediately. In this example, the control box 21 and the sensor unit 201A are separate, but the sensor unit 201A may be provided in the control box 21 and integrated.

  In the mirror-cooled dew point meter 201 shown in FIG. 1, the tube 17 containing the light-emitting side optical fiber 17-1 and the light-receiving side optical fiber 17-2 is used in the sensor unit 201A. As shown in the sensor unit 201A ′, a light emitting diode 19 may be provided instead of the light-emitting side optical fiber 17-1, and a photocoupler 20 may be provided instead of the light-receiving side optical fiber 17-2.

[Embodiment 2: Mirror Surface Cooling Dew Point Meter (Specular Reflection Light Detection Method)]
FIG. 6 is a schematic configuration diagram of a mirror-cooled dew point meter showing another embodiment of the moisture detection device according to the present invention. In the mirror-cooled dew point meter 202, the light-emitting side optical fiber 17-1 and the light-receiving side optical fiber 17-2 are not coaxial, but are provided symmetrically on the left and right sides of the mirror 10. The tips of the light-emitting side optical fiber 17-1 and the light-receiving side optical fiber 17-2, which are curved in a J-shape, are directed to the mirror surface 10-1 of the mirror 10 and symmetrical with respect to the mirror surface 10-1. Is inclined at a predetermined inclination angle.

  In this mirror-cooled dew point meter 202, the sensor unit 202A is placed in the gas to be measured. In addition, the dew condensation detection unit 13 irradiates the mirror surface 10-1 of the mirror 10 with pulsed light obliquely at a predetermined cycle from the tip of the optical fiber 17-1. If the mirror surface 10-1 is exposed to the gas to be measured and no condensation occurs on the mirror surface 10-1, almost all of the pulsed light irradiated from the tip of the optical fiber 17-1 is regularly reflected. Light is received through the optical fiber 17-2. Therefore, when no condensation occurs on the mirror surface 10-1, the intensity of the reflected pulse light received through the optical fiber 17-2 is high.

  In the dew condensation detector 13, the difference between the upper limit value and the lower limit value of the reflected pulse light received through the optical fiber 17-2 is obtained as the intensity of the reflected pulse light, and a signal S1 corresponding to the intensity of the reflected pulse light is obtained. The data is sent to the Peltier output control unit 14. In this case, since the intensity of the reflected pulse light is large and exceeds the threshold value, the Peltier output control unit 14 sends a control signal S2 for increasing the current to the thermoelectric cooling element 2 to the signal conversion unit 15. Thereby, the current S3 from the signal converter 15 to the thermoelectric cooling element 2 increases, and the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is lowered.

  When the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is lowered, that is, the temperature of the mirror 10, the water vapor contained in the gas to be measured is condensed on the mirror surface 10-1 of the mirror 10, and the water molecules are optical fiber. Part of the pulsed light irradiated from the tip portion of 17-1 is absorbed or irregularly reflected. Thereby, the intensity | strength of the reflected pulsed light (regular reflected light) from the mirror surface 10-1 light-received via the optical fiber 17-2 reduces.

  Here, when the intensity of the reflected pulsed light received through the optical fiber 17-2 falls below the threshold value, the Peltier output control unit 14 sends the control signal S2 for reducing the current to the thermoelectric cooling element 2 to the signal conversion unit 15. Send to. Thereby, the fall of the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is suppressed, and generation | occurrence | production of dew condensation is suppressed. By suppressing the dew condensation, the intensity of the reflected pulse light received through the optical fiber 17-2 increases. When the intensity exceeds the threshold, the control signal S2 increases the current from the Peltier output control unit 14 to the thermoelectric cooling element 2. Is sent to the signal converter 15. By repeating this operation, the temperature of the cooling surface 2-1 of the thermoelectric cooling element 2 is adjusted so that the intensity of the reflected pulse light received through the optical fiber 17-2 is approximately equal to the threshold value. The adjusted temperature, that is, the temperature at which the dew condensation that has occurred on the mirror surface 10-1 has reached an equilibrium state (dew point temperature) is displayed on the dew point temperature display unit 12 as the dew point temperature.

Also in this mirror-cooled dew point meter 202, the malfunction is prevented by disturbance light in the dew condensation detection unit 13 by the pulse modulation method, so that the chamber can be eliminated from the sensor unit 202A.
In the first and second embodiments described above, the condensation (moisture) generated on the mirror surface 10-1 is detected. However, the frost (moisture) generated on the mirror surface 10-1 can also be detected by the same configuration. Is possible.
In the first and second embodiments described above, the thermoelectric cooling element (Peltier element) 2 is used as the cooling means for cooling the mirror 10, but a helium refrigerator or the like may be used.

[ Reference Example 1 : Weather meter (scattered light detection method)]
FIG. 7 is a schematic configuration diagram of a weather meter showing a reference example of a mirror-cooled dew point meter according to the present invention. The weather gauge 203 includes a sensor unit 203A and a rain detection unit 203B. The sensor unit 203A has a configuration in which only the mirror 10 is provided, and a tube 17 whose upper end is curved in a J-shape is provided in the same manner as in the first embodiment.

  In this weather gauge 203, the rain detection unit 203B irradiates the mirror surface 10-1 of the mirror 10 with pulse light obliquely at a predetermined cycle from the tip of the optical fiber 17-1, and the optical fiber 17-2. The difference between the upper limit value and the lower limit value of the reflected pulse light (scattered light) received through the light source is obtained as the intensity of the reflected pulse light, and the intensity of the reflected pulse light is compared with a predetermined threshold value. When the light intensity exceeds the threshold, it is determined that it has started to rain (rain has been attached to the mirror surface 10-1).

[ Reference Example 2 : Weather meter (regular reflection light method)]
FIG. 8 is a schematic configuration diagram of a weather meter showing another reference example of the mirror-cooled dew point meter according to the present invention. The weather gauge 204 includes a sensor unit 204A and a rain detection unit 204B. The sensor unit 204A has a configuration in which only the mirror 10 is provided, and in the same manner as in the second embodiment, the issue-side optical fiber 17-1 and the light-receiving side optical fiber 17-2 whose upper ends are curved in a J-shape. Are provided symmetrically with the mirror 10 in between.

  In this weather gauge 204, the rain detection unit 204B irradiates the mirror surface 10-1 of the mirror 10 with pulse light obliquely at a predetermined cycle from the tip of the optical fiber 17-1, and the optical fiber 17-2. The difference between the upper limit value and the lower limit value of the reflected pulsed light (regular reflected light) received through the light is obtained as the intensity of the reflected pulsed light, the intensity of the reflected pulsed light is compared with a predetermined threshold value, and the reflected light is reflected. When the intensity of the pulsed light falls below the threshold, it is determined that it has started to rain (rain has been attached to the mirror surface 10-1).

In the reference examples 1 and 2 described above, rain attached to the mirror surface 10-1 can be detected. However, it is also possible to detect snow attached to the mirror surface 10-1 with the same configuration. In addition, with the same configuration, it is possible to detect not only rain and snow but also dust and the like.

It is a schematic block diagram (Embodiment 1) which shows one Embodiment of the mirror surface cooling-type dew point meter which concerns on this invention. It is a figure which illustrates the structure which provides the optical fiber of a light emission side, and the optical fiber of a light reception side coaxially in one tube. It is a figure which shows the pulsed light irradiated with respect to a mirror surface, and the reflected pulsed light received from a mirror surface. It is a figure which shows the structure of the mirror surface dew point meter which accommodated the control part in the control box. It is a figure which shows the modification of the sensor part of the mirror surface cooling-type dew point meter of Embodiment 1. FIG. It is a schematic block diagram (Embodiment 2) which shows other embodiment of the mirror surface cooling type dew point meter which concerns on this invention. It is a schematic block diagram (Embodiment 3) of the weather meter which shows one reference example of the mirror surface cooling-type dew point meter which concerns on this invention. It is a schematic block diagram (Embodiment 4) of the weather meter which shows the other reference example of the mirror surface cooling dew point meter which concerns on this invention. It is a figure which shows the principal part of 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 principal part of the conventional mirror surface cooling-type dew point meter which employ | adopted the scattered light detection system. It is a figure which shows the principal part of the conventional weather meter which employ | adopted the regular reflection light detection system. It is a figure which shows the principal part of the conventional weather meter which employ | adopted the scattered light detection system. It is a perspective view which shows the attachment structure of the mirror and temperature detection element in the conventional mirror surface cooling dew point meter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Thermoelectric cooling element (Peltier element), 2-1 ... Cooling surface, 2-2 ... Heating surface, 10 ... Mirror, 10-1 ... Mirror surface, 11 ... Temperature detection element (thin film resistance thermometer), 12 ... Dew point Temperature display unit, 13 ... dew condensation detection unit, 14 ... Peltier output control unit, 15 ... signal conversion unit, 17 ... tube, 17-1 ... light-emitting side optical fiber, 17-2 ... light-receiving side optical fiber, 18 ... heat sink , 19 ... Light emitting diode, 20 ... Photocoupler, 21 ... Control box, 40 ... Insulation, 201, 202 ... Mirror surface dew point meter, 201A, 202A, 202A '... Sensor unit, 201B, 202B ... Control unit, 203, 204 ... Weather meter, 203A, 204A ... Sensor unit, 203B, 204B ... Rain detection unit.

Claims (1)

A mirror whose mirror surface is exposed to the gas to be measured;
Cooling means for cooling the mirror;
A light emitting means for irradiating the mirror surface with pulsed light at a predetermined period;
A light receiving means for receiving the reflected light of the pulsed light emitted from the light emitting means to the mirror surface;
Means for detecting moisture generated on the mirror surface of the mirror cooled by the cooling means based on the reflected light received by the light receiving means;
In the mirror-cooled dew point meter provided with a temperature detecting element for detecting the temperature of the mirror,
Means for detecting moisture generated on the mirror surface of the mirror cooled by the cooling means based on a difference between an upper limit value and a lower limit value for each pulse of reflected light received by the light receiving means;
A mirror-cooled dew point meter, characterized in that it does not include a chamber portion that blocks ambient light.

Images