RU1784901C - Moisture thermoelectric gauge - Google Patents

Abstract

Usage: measuring equipment, instrumentation. The thermoelectric humidity sensor contains a semiconductor sensing element in the form of contact branches forming dry and wet, in contact with the porous wettable material, thermometers connected to the measuring device. The sensitive element is made of a needle-shaped tellurium single crystal, to the tip of which a porous wettable material is pressed in the form of a paper strip, and the contact branches are formed by welding to the sensitive element of the gold microwire. 2 ill.

Description

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WITH

The invention relates to a measurement technique, namely, psychrometric thermoelectric sensors measuring relative humidity.

Psychometric humidity sensors are known containing dry and wet thermometers, the measured temperature difference between which is proportional to the relative humidity of the air. As thermometers use thermocouples, thermistors (including semiconductor). A wet thermometer is coated with a porous material fed with water in a continuous or in a dosed mode.

. Psychometric thermoelectric humidity sensors are known that contain a semiconductor sensitive element, made, for example, in the form of micromodules, the contact branches of which form dry and wet thermometers, which are connected to a measuring circuit or a recording device. On the surface of the wet junctions of the micromodule there is a tray of heat-conducting material with a wettable plate placed in it.

Their disadvantage is a relatively large inertia - 12 - 35 s, with the number of semiconductor branches 64, the size of the sensor 4.9 4.9 2.6 mm3.

An object of the invention is to increase speed.

To achieve this, a thermoelectric humidity sensor comprising a semiconductor sensing element, to which are connected contact branches forming dry and wet thermometers connected to the measuring device, and a porous wettable material in contact with

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ABOUT

With a wet thermometer according to the invention, the sensing element is made of needle-shaped tellurium single crystal, the tip of which is in contact with the porous wettable material.

Figure 1 shows a diagram of a thermoelectric humidity sensor; figure 2 - its calibration characteristic.

Sensor Contains a sensing element t, contact branches 2, holder 3, lamels 4; connecting wires 5, measuring device 6, porous wettable material 7, humidifier 8.

The invention is as follows. To the sensitive element 1, which is a needle single crystal Te with a free carrier concentration of 1017 cm 3, grown by the method of chemical transport reactions, with an average size of 5.0-0.20-0.25 mm3, tip diameter: 0.0.1 mm, created contact branches 2 by welding a gold microwire with a diameter of 0.01-0.03 mm. On the dielectric holder 3, lamellas 4 are installed, to which the ends of the contact branches are connected 2. To the lamellas 3 are also connected wires 5 connecting the sensing element 1 with the measuring device 6, which was used as a digital voltmeter 87-21 A. On rust 3 a porous wettable material 7 is also installed in the form of a strip of filter paper pressed against the tip of the sensing element 1. The strip 7 is wetted either with a humidifier 8, which is an installed water can, or a specialist nym drip spout.

The sensor was calibrated in a temperature and humidity test chamber Plaflnous PR-3E from Tabaf, in which a relative humidity of 20–100% and a temperature of 20–85 ° C were set. Figure 2 shows the dependence of the output signal of the sensor on the relative humidity

air f at temperatures of 20, 40 and 60 ° С, to which curves 9, 10, 11 correspond. Thermometers are used for this, or a part of the sensor element 1 operating in the thermistor mode is used. Then, according to the readings of digital voltmeter b, the relative humidity of the air is determined using the graph of Fig. 2 with appropriate interpolation. For the convenience of work, it is possible to construct psychrometric tables, or use an analytical dependence of the form:

f - f20 ° c + crAt%

where a is the average temperature coefficient, for a temperature range of 20-40 ° C9 is 0.33% / ° C, f20 ° c is relative humidity at 20 ° C, At is the temperature deviation from 20 ° C. In this case, only one calibration curve 9 of FIG. 2 is used.

Claims (1)

The sensor can be used for measurements in small volumes; its inertia does not exceed 1 s. For measurements in dusty environments, the sensor element is protected with a thin layer of varnish. SUMMARY OF THE INVENTION A thermoelectric humidity sensor comprising a semiconductor sensing element, to which are connected contact branches forming a dry and wet thermometer connected to a measuring device, and a porous wettable material in contact with a wet thermometer, characterized in that, in order to increase speed , the sensing element is made of a needle-shaped tellurium single crystal whose tip is in contact with a porous wettable material. Srig. 1