JPH0618954U - Gas concentration measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose of measuring the gas concentration using infrared rays is to stabilize the behavior of the output of the infrared detection element even when the outside air temperature fluctuates. [Structure] The outer periphery of an infrared sensor having an infrared detection element is covered with a heat insulating material. With this coating, even if the outside air temperature fluctuates, the output of the infrared detection element does not fluctuate, and the behavior of the output is stable.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a gas concentration measuring device using a pyroelectric infrared sensor.

[0002]

[Prior art]

 As is well known, this type of gas concentration measuring device is composed of a gas cell that stores the gas to be measured, an infrared radiation source installed at one end of the gas cell, and a pyroelectric infrared sensor installed at the other end. It is mainly composed of and. Infrared rays from the infrared radiation source pass through the gas cell and irradiate the pyroelectric infrared detection element that constitutes the infrared sensor, and the gas concentration is measured from the output from this infrared detection element. I am trying.

By the way, this infrared detecting element is usually mounted only on the surface of the printed circuit board inside the infrared sensor. However, since this infrared detection element has temperature characteristics, it is easily affected by changes in the outside air temperature at the installation location of this type of gas concentration measuring device, and therefore the sensor output changes due to changes in the outside air temperature. , Measurement error may occur.

[0004]

[Problems to be solved by the device]

 An object of the present invention is to improve measurement accuracy by suppressing the behavior of the sensor output due to changes in the outside air temperature.

[0005]

[Means for Solving the Problems]

 The present invention is a gas concentration measuring device that transmits infrared rays to a gas to be measured, and measures the concentration of the gas from the change in the amount of infrared rays transmitted by the gas's unique absorption infrared wavelength. An infrared radiation source is installed at one end of the cell, and the infrared light that has passed through the gas is incident on the other end of the cell, and an infrared sensor equipped with an infrared detection element that detects the amount of the infrared light transmitted is installed. The outer periphery of the infrared sensor is coated with a heat insulating material.

[0006]

[Action]

 By covering the outer circumference of the infrared sensor with a heat insulating material, the infrared detecting element is less susceptible to fluctuations in the ambient temperature. Therefore, the behavior of the sensor output due to changes in the outside air temperature is suppressed and becomes smaller. This will improve the measurement accuracy.

[0007]

【Example】

 An embodiment of this invention will be described with reference to FIG. Reference numeral 1 is a cell in which a gas to be measured is stored, 2 is an inlet thereof, 3 is an outlet, 4 is an infrared radiation source, 5 and 6 are filters which transmit only infrared rays having an absorption wavelength peculiar to the gas to be measured. Indicated by 7 and 7 are infrared sensors, which are composed of an infrared ray detecting element 8, a chopper 9 for making the infrared rays incident on the infrared ray detecting element 8 intermittent light, and a motor 10 for rotating the chopper 9.

These configurations are not particularly different from the conventional ones, and the infrared rays from the infrared radiation source 4 pass through the gas in the cell 1 and are made into intermittent light by the chopper 9, and the infrared ray detecting element 8 is used. Is incident on. Infrared rays of a specific wavelength absorbed by the gas to be measured are absorbed by the gas, but the amount of absorption changes depending on the concentration of the gas. Therefore, the concentration of the gas can be measured from the sensor output according to the infrared ray amount of the specific wavelength detected by the infrared ray detecting element 8.

According to the present invention, the outer circumference of the infrared sensor 7 is covered with a heat insulating material 11 such as styrofoam or asbestos. With such a configuration, even if the outside air temperature fluctuates, the heat insulating material 11 makes the infrared detection element 8 of the infrared sensor 7 less susceptible to the temperature change. Therefore, the behavior of the sensor output from now on becomes stable.

FIG. 2 shows the variation of the sensor output with respect to time according to the present invention, and FIG. 3 shows the variation of the sensor output in the case of the conventional configuration in which the heat insulating material 11 is not used. Comparing both figures, it is found that the unstable behavior of the sensor output is reduced when the heat insulating material 11 is provided according to the present invention.

As shown in FIG. 1, a heat insulating material 12 is interposed between the infrared radiation source 4 and the cell 1 so that heat from the infrared radiation source 4 is not conducted to the infrared sensor 7 through the cell 1. It is good to do so.

[0012]

[Effect of device]

 As described above in detail, according to the present invention, in measuring the gas concentration using infrared rays, the outer circumference of the infrared sensor equipped with the infrared detecting element on which the infrared rays transmitted through the gas to be measured are incident is insulated. Since it is covered with a material, the behavior of the sensor output does not become unstable due to the influence of fluctuations in the outside air temperature even when an infrared ray detection element with temperature characteristics is used. It has the effect that the concentration can be measured accurately.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a sensor output according to the present invention with respect to time.

FIG. 3 is a characteristic diagram of a sensor output with respect to time according to a conventional configuration.

[Explanation of symbols]

 1 cell 4 infrared radiation source 5 infrared light source 7 infrared sensor 8 infrared detection element 11 heat insulating material

Claims (1)

[Scope of utility model registration request] 1. An infrared ray is transmitted through a gas to be measured,
In a gas concentration measuring device for measuring the concentration of the gas from the change in the amount of infrared transmission of the absorption infrared wavelength peculiar to the gas, an infrared radiation source is provided at one end of the cell containing the gas, and the other end is also provided. Infrared rays that have passed through the gas are incident on the section, and an infrared sensor equipped with an infrared detection element that detects the amount of transmitted infrared rays is installed, and the outer periphery of the infrared sensor is covered with a heat insulating material to measure the gas concentration. apparatus.