JP2003194756A - Mirror-surface condensing dew-point instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mirror-surface condensing dew-point instrument that can accurately measure the dew point of a gas having a high dew point. <P>SOLUTION: This mirror-surface condensing dew-point instrument has a reflecting mirror positioned in a housing forming the flow passage of a measuring gas. In this instrument, the influence of a gas to be measured upon a reference light measuring system and a reflected light measuring system is eliminated by arranging the systems on the outside of the housing. The reference light measuring system is composed of a first light source section and a first light receiving section which receives straight advancing light from the light source section. The reflected light measuring system is composed of a second light source section which sends light to the reflecting mirror, and a second light receiving section which receives the reflected light from the reflecting mirror. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror-cooled dew point meter capable of accurately measuring the dew point of a gas having a high dew point (condensation temperature). [0002] Gas humidity measuring devices include a psychrometer,
Lithium chloride dew point meters, capacitance type humidity sensors, mirror surface cooled dew point meters, and the like are known. Among these humidity measuring instruments, a mirror-cooled dew point meter, which is a primary detection method for directly measuring the dew point of a gas, has high measurement accuracy and high reliability. In a known mirror-cooled dew point meter, the temperature is controlled by temperature control means such as a Peltier element or a reference light measuring system including a light source element and a light receiving element in a housing forming a gas flow path to be measured. It has a structure in which a main component is a measuring light measuring system including a reflecting mirror and a light source element and a light receiving element arranged close to the reflecting mirror. This type of dew point meter uses a light measuring system for the reference light measurement system because if the surface temperature of the reflecting mirror falls below the dew point (or frost point) of the gas to be measured, the optical reflectance of the reflecting mirror surface decreases due to condensation. This is based on the principle that the dew point is determined by comparing the amount of light received by the element and the amount of light received by the light receiving element of the measuring light measurement system. However, the known mirror-cooled dew point meter is limited by the endurance temperature of a light source element (for example, a light emitting diode) and a light receiving element (for example, a phototransistor) arranged close to a reflecting mirror. The upper limit of the possible dew point is around 100 ° C. That is, in principle, the mirror-cooled dew point meter requires that the temperature of the mirror surface portion and its vicinity be matched with the dew point temperature of the gas to be measured. Therefore, when the dew point temperature of the gas to be measured is higher than the usable temperatures of the light source element and the light receiving element, the dew point measurement of the gas cannot be performed. Accordingly, an object of the present invention is to provide a mirror-cooled dew point meter capable of accurately measuring the dew point of a gas having a high dew point. Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the outside of a housing forming a gas flow path to be measured of a mirror-cooled dew point meter has been studied. It has been found that the object can be achieved by installing a light source element and a light receiving element in a normal temperature / normal pressure environment. That is, the present invention provides the following mirror-cooled dew point meter. 1. In a mirror-cooled dew point meter in which a reflecting mirror is arranged in a housing forming a measurement gas flow path, a first light source unit and a reference light measurement system including a first light receiving unit that receives straight light from the light source unit, By arranging, outside the housing, a second light source unit for transmitting light to the reflecting mirror and a reflected light measuring system including a second light receiving unit for receiving reflected light from the reflecting mirror, the gas to be measured for the two light measuring systems A mirror-cooled dew point meter characterized by eliminating the effects of Hereinafter, the present invention will be described in more detail with reference to a schematic sectional view schematically showing an embodiment of the present invention. As shown in FIG. 1, in a mirror-cooled dew point meter (hereinafter simply referred to as "dew point meter") according to the present invention, a flow path of a gas to be measured is formed in a housing as in a known dew point meter. The mirror surface of the reflecting mirror is arranged at a position where it is in direct contact with the gas. [0010] The control light is emitted from a first light source unit or a light source element (for example, a light emitting diode) provided outside the housing.
After going straight through the optical path for measurement in the housing via the optical fiber as a probe, the light reaches the first light receiving portion or the light receiving element arranged outside the housing again via the optical fiber. The measuring light is incident on the mirror surface of the reflecting mirror via the optical fiber from the second light source unit or the light source element (for example, light emitting diode) provided outside the housing, is reflected by the mirror surface, and is again reflected on the optical fiber. Through the second light receiving portion and the light receiving element disposed outside the housing. The reflecting mirror has a heat pump, and the temperature is controlled by a heat pump control circuit as described later. When the gas to be measured introduced into the gas flow path in the housing comes into contact with the reflecting mirror and dew or frost is formed on the mirror surface, the amount of reflected light reaching the second light receiving portion decreases. . Therefore, in the comparison / arithmetic circuit incorporated in the heat pump control circuit, the light amount at the first light receiving unit is compared with the light amount at the second light receiving unit, and based on the calculation result,
The temperature of the mirror surface is adjusted by controlling the cooling capacity of the heat pump so that the amount of dew or frost on the mirror surface is constant. The temperature data of the mirror surface is processed by a temperature measurement circuit through a temperature measuring element, and the temperature is displayed. In this way, the mirror surface temperature when the amount of dew or frost is constant becomes the dew point or frost point. Although FIG. 1 shows a device in which a converging lens is attached to the tip of the optical fiber in the housing to improve optical coupling, good results can be obtained without using a converging lens. Can be omitted when is obtained. It is also possible to attach the optical fiber tip or the condenser lens to the housing wall without extending it into the housing. According to the present invention, since the light source element and the light receiving element are installed in a normal temperature / normal pressure environment, the upper limit of the dew point of the gas to be measured is limited to the usable temperature of these optical elements. You are not restricted. Therefore, the dew point of 300 ° C. or more can be measured in consideration of the heat resistant temperature of the optical fiber probe and the heat pump.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view schematically showing an embodiment of the present invention.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kazuaki Yasuda             1-8-3 Midorioka, Ikeda-shi, Osaka Independent line             AIST Kansai Center F term (reference) 2G040 AA04 AB03 BA23 BB04 CA12                       CA23 DA01 EA01 HA05

Claims (1)

Claims: 1. A mirror-cooled dew point meter in which a reflecting mirror is arranged in a housing forming a gas flow path to be measured, a first light source unit and a second light source receiving straight light from the light source unit. A reference light measuring system including one light receiving unit and a reflected light measuring system including a second light source unit for transmitting light to the reflecting mirror and a second light receiving unit receiving reflected light from the reflecting mirror are disposed outside the housing. The mirror-cooled dew point meter eliminates the influence of the gas to be measured on the two optical measurement systems.