RU63930U1 - PRESSURE PRESSURE PRESSURE SENSOR - Google Patents

Abstract

The proposed utility model relates to measurement technique. The purpose of the utility model is to create a partial pressure sensor for measuring water vapor in the range from 0 to 13.3 Pa. The sensor is based on the electrolytic measurement method. The essence of this method is the absorption of water vapor molecules falling from atmospheric air to the working surface of the sensor. The working surface of the sensor consists of a cylindrical glass tube, two platinum electrodes made in the form of helicoidal non-contacting spirals, the gap between which is filled with a sorbent film of phosphoric anhydride. Under the influence of a DC voltage applied to the electrodes, electrolytic decomposition of water vapor into hydrogen and oxygen occurs. New to the partial pressure sensor for water vapor is that the mass transfer of water vapor molecules from atmospheric air to the external surface of the working part of the sensor, and the electrolysis current is determined by the partial pressure of water vapor, temperature and geometric dimensions of the working part of the sensor. The proposed sensor is illustrated in the drawing. Technical specifications are confirmed by two tables.

Description

The utility model relates to measuring technique and can be used to measure the partial pressure of water vapor in the range from 0 to 13.3 Pa in atmospheric air at pressures from 1.33 · 10 ^-1 to 1.07 · 10 ⁵ Pa.

Known humidity sensors of the resistive type (RF patent No. 2109778 6 C 08 L 79/08), sorption-frequency type (technical conditions 5K0.155.010 TU) and sorption-capacitive type (http://www.miczofor.ru/public/tezis_iva9 .htm)

Resistive and sorption-frequency sensors have a low sensitivity and are used when measuring relative air humidity in the range from 0 to 100%.

Sorption-capacitive type sensors measure ultra-low concentrations of water vapor in the range from -100 ° St. to -60 ° St. R., but operate in a flowing medium of the analyzed gas.

Closest to the claimed sensor is a coulometric cell (a.s. As the sorbent film, for example, a film of partially hydrated phosphorus anhydride P ₂ O _{5 is used} . To the electrodes, through the terminals on the outer surface of the housing, a DC voltage is applied.

The analyzed gas is passed through the internal channel of the housing from the side of the working part. Two processes continuously occur in the cell: the almost complete absorption of moisture by a film of a hygroscopic substance with the formation of phosphoric acid and the electrolysis of water for oxygen and hydrogen with the regeneration of phosphoric anhydride.

P ₂ O ₅ + H ₂ O → 2HPO ₃

2НРО ₃ → Н ₂ + 1 / 2O ₂ + Р ₂ O ₅

At a constant gas flow rate according to the Faraday law, the electrolysis current is proportional to the volume fraction of moisture contained in the analyzed gas.

The sensor using a coulometric cell allows you to measure ultra-low moisture concentrations, but the analyzed gas must flow into the internal channel of the coulometric cell with a constant flow rate.

The essence of the utility model is that the partial pressure sensor for water vapor, consisting of a cylindrical glass tube, on the outer surface of which there are two helicoidal non-contacting spirals, and the spaces between them are filled with a sorbent film, differs from the prototype in that the mass transfer of water vapor molecules from atmospheric air is carried out on the external surface of the working part of the sensor, and the electrolysis current is determined by the partial pressure of water vapor, temperature and geometric dimensions ramie working sensor parts.

where I is the electrolysis current, A;

is the arithmetic average speed of water vapor molecules, ;

R is the molar (universal) gas constant, ;

T is the surface temperature of the working part of the sensor, K;

M is the molar mass of water vapor, ;

- partial pressure of water vapor in atmospheric air, Pa;

D is the cylinder diameter of the tube of the working part of the sensor, m;

L is the length of the working part of the sensor, m;

e is the electron charge, C;

n is the number of electrochemically decomposed molecules of water vapor per unit time, ;

N is the mass of water vapor molecules falling on the active surface of the working part of the sensor per unit time, ;

m is the relative molecular weight of one electrochemically decomposed water vapor molecule.

The figure shows a drawing of a partial pressure sensor for water vapor, which is based on the electrolytic method of measurement, the essence of which is the absorption of water vapor molecules falling from

atmospheric air to the working surface of the sensor. It consists of a cylindrical glass tube 1, two platinum electrodes 2, made in the form of helicoidal non-contacting spirals, the gap between which is filled with a sorbent film of phosphoric anhydride. Under the influence of a DC voltage applied to the electrodes, electrolytic decomposition of water vapor into hydrogen and oxygen occurs. Inside the tube is a heater 3, which, together with a temperature sensor on the thermistor 4 and a resistance thermometer 5, thermostat the sensor at positive temperatures. The conclusions of all the sensor elements are sealed on contacts 6, pressed into a fluoroplastic sleeve of complex shape 7, which fixes the glass tube relative to the housing 8 using screws 9 and a step washer 10.

To confirm the industrial applicability of the utility model of the partial pressure sensor for water vapor, the following tests were carried out:

1. Definition of the basic reduced error (table 1)

2. The determination of the time constant (table. 2)

The tests carried out confirm the possibility of measuring the partial pressure of water vapor in the range from 0 to 13.3 Pa with a basic reduced error of ± 10%.

Tables

Table 1 Sensor Number Range of measurements, Pa Partial pressure of water vapor, Pa The main reduced error,% Valid Measured one 4.6 · 10 ^-2 4,51 2 0 ... 1.3310 ^-1 4 · 10 ^-2 5.0510 ^-2 7.89 3 5.3 · 10 ^-2 9.78 one 3.1 · 10 ^-1 5.26 2 0 ... 1.33 2.4 · 10 ^-1 3.4 · 10 ^-1 7.52 3 3.1 · 10 ^-1 7.52 one 4.2 6.02 2 0 ... 13.3 3.4 3,7 2.26 3 4.2 6.02 table 2 Sensor Number Range of measurements, Pa Time constant, s With increasing partial pressure of water vapor With a decrease in the partial pressure of water vapor one 0 ... 1.3310 ^-1 2,5 1,0

Claims (1)

Partial pressure sensor for water vapor, consisting of a cylindrical glass tube, characterized in that on the outer surface there are two platinum electrodes in the form of helicoidal non-contacting spirals, the gaps between them are filled with a sorbent film of phosphoric anhydride, and the partial pressure of water vapor at a stable positive temperature and selected geometric dimensions is determined by the magnitude of the electrolysis current of water vapor molecules falling on the working surface of the sensor.