JPS629854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical dew point detection device. Generally, the dew point of a gas can be determined by cooling an object in a gas and measuring the temperature of the surface when dew begins to form on the surface. As a device for detecting this dew point, an optical dew point detection device is often used.

Optical dew point detection devices place a light reflector such as a metal mirror whose temperature is controlled by electronic cooling using a thermo module in the gas to be measured, and project light onto the light reflector to detect the target. The dew point of the gas to be measured is measured by measuring the temperature of the light reflector when the moisture in the gas to be measured begins to condense on the surface of the light reflector and the amount of reflected light decreases.

As described above, the optical dew point detection device detects a decrease in the amount of reflected light due to dew condensation, and in order to improve the sensitivity of the device, it is desired that the decrease in the amount of reflected light due to dew condensation be outputted noticeably.

The present invention has been made in view of the above, and uses a transparent object instead of the light reflector of a conventional optical dew point detection device, and projects light onto this transparent object to detect both the light entrance and exit surfaces of the object. The degree of light scattering caused by dew condensation is increased, and as a result, the decreased amount of transmitted light is outputted significantly, thereby improving sensitivity.

Hereinafter, the present invention will be explained in detail in comparison with a conventional device with reference to the accompanying drawings.

FIG. 1 is a system diagram showing an example of a conventional optical dew point detection device. Light reflectors 4 and 5 such as metal mirrors are arranged in a case 1 containing the gas to be measured, and only one light reflector 4 is electronically cooled with a temperature control device 2 such as a thermo module, and a temperature measuring element 3 is cooled. The temperature of the surface of the light reflector 4 is measured. Light from light sources 6 and 7 such as light emitting diodes and lamps is projected onto light reflectors 4 and 5, respectively, and each reflected light is received by photodetectors 8 and 9 such as photodiodes and phototransistors, respectively, and the amount of each received light is calculated. Comparison amplifier 10 compares and amplifies and outputs. When the light reflector 4 is gradually cooled while the gas to be measured is introduced into the case 1, dew condensation occurs on the surface of the light reflector, the amount of reflected light decreases, and the balance between the amount of light received by the photodetectors 8 and 9 is lost. An output is provided to comparison amplifier 10. The temperature of the light reflector 4 at that time is measured by the temperature measuring element 3 and determined as the dew point.

FIG. 2 is a system diagram showing an example of the optical dew point detection device of the present invention. Case 2 containing gas to be measured
Inside 1, there is a rod-shaped transparent object 2 such as quartz or glass.
4 and 25 are inserted and arranged in metal bodies 31 and 32 having good thermal conductivity, such as copper and brass, respectively. One metal body 31 is electronically cooled with a temperature control device 22 such as a thermo module to cool the transparent object 24,
The temperature of the surface is measured by the temperature measuring element 23. Both end surfaces 33, 34 and 35, 36 of the transparent objects 24, 25 are both flat-polished, and light from light sources 26, 27 such as light emitting diodes and lamps is transmitted to the end surfaces 33, 35.
The light transmitted through transparent objects 24 and 25 is received by photodetectors 28 and 29, such as photodiodes and phototransistors, respectively, and the amounts of each received light are compared and amplified by a comparison amplifier 30 and output.

Now, when the transparent object 24 is gradually cooled through the metal body 31 by the temperature control device 22, the end surface 3
Condensation occurs on 3 and 34. The light from the light source 26 is scattered by condensation on the end face 33 on the incident side, and then further scattered by the condensation on the end face 34 on the output side, so that the light transmitted through the transparent object undergoes two scattering phenomena. It turns out. As a result, the amount of light received by the photodetector 28 is reduced by approximately half compared to when a conventional reflector is used, and the output difference of the balanced comparison amplifier 30 becomes larger, allowing dew point detection with higher sensitivity. be able to.

As mentioned above, the present invention detects the decrease in the amount of transmitted light due to the two-time light scattering phenomenon caused by dew condensation on both end faces of a transparent object. Compared to detecting a decrease in the amount of light, the dew point can be detected with higher sensitivity, and the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a conventional optical dew point detection device, and FIG. 2 is a system diagram showing an example of the dew point detection device of the present invention. Codes in the diagram: 1, 21... Case, 4, 5... Light reflector, 2, 22... Temperature adjustment device, 24, 25... Transparent object, 3, 23... Temperature measuring element, 6, 7, 26, 27
...Light source, 8,9,28,29...Photodetector, 31,
32... Metal body, 10, 30... Comparison amplifier, 33,
34, 35, 36... end surface.

Claims (1)

[Claims] 1. A transparent object placed in an enclosed space containing the gas whose dew point is to be measured, a light source that projects light onto the transparent object, and a light source that receives the light transmitted through the transparent object, and as the temperature of the transparent object decreases, the temperature of the object decreases. A dew point detection device comprising a device that detects a decrease in the amount of transmitted light due to dew condensation on the light entrance and exit surfaces.