RU2583872C1 - Hygrometer - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: invention relates to analytical instrument making and can be used in making hygrometers employing coulometric cell for measurement of volume fraction of moisture (MVF). Humidity indicator includes unit for generating gas stream and coulometric cell. In order to increase service life of hygrometer analysed gas can be supplied both from working part, and from side of coulometric cell control part.

EFFECT: longer service life of hygrometer.

1 cl, 1 dwg

Description

The invention relates to the field of analytical instrumentation and can be used in the device of hygrometers using a coulometric cell to measure the volume fraction of moisture (EFA).

A known method of incorporating a coulometric cell (patent No. 2498285, class G01N 27/07) used in coulometric hygrometers, consisting of two parts: working and control, located in the inner channel of the glass case.

A known hygrometer (patent No. 2413935, class G01N 27/07) containing a sensor including a flow forming unit with a gas flow stabilizer, coulometric cell, consisting of two parts: working and control, located one after another in a glass case, the ratio of the lengths of the control and working at least 1/3.

The entire inner surface in the glass case is covered with a thin layer of partially hydrated phosphorus pentoxide, actively absorbing moisture from the passing analyzed gas.

и определяемой по формуле 1:The moisture contained in the analyzed gas is supplied to the working part, then to the control part, is absorbed by the sorbent film and undergoes electrolysis under the influence of a voltage from a direct current source applied to the electrodes of the coulometric cell. The total moisture electrolysis current of the working and control parts of the coulometric cell at a constant gas flow rate is proportional to the volume fraction of moisture contained in the analyzed gas $$\left({\text{B}}_{{\text{H}}_{\text{2}}\text{O}}\right)$$

and determined by the formula 1:

- объемная доля влаги в анализируемом газе;Where $${\text{B}}_{{\text{H}}_{\text{2}}\text{O}}$$

- volume fraction of moisture in the analyzed gas;

- электрохимический эквивалент воды; $${\text{E}}_{{\text{H}}_{\text{2}}\text{O}}$$

- electrochemical equivalent of water;

Q is the gas flow rate;

I ₀ is the total moisture electrolysis current of the working and control parts of the coulometric cell.

The disadvantage of this hygrometer is that the service life of the coulometric cell depends on the concentration of the EFA in the analyzed gas. The electrolysis density in the first turns of the cell will be much higher than in the whole cell, which leads to heating of the initial section of the cell and the appearance of jumpers between the electrodes.

The goal of increasing the life of coulometric cell is achieved in that depending on the content of the EFA sample gas may be supplied both from the working part of coulometric cell in the measurement of small concentrations of EFA ^-1 to 100 million, and by the control portion when measuring a concentration of 100 million ^-1 .

In FIG. 1 shows a schematic diagram of a hygrometer device with a gas flow forming unit and a coulometric cell.

The hygrometer forming unit includes: 1 inlet fitting for supplying the analyzed gas of less than 100 ppm ^-1 ODV, 2 pneumatic resistance, 3 upstream pressure stabilizer, 4 pneumatic resistance, 5 coulometric cell, 6 analyzed gas outlet fitting (bypass ), 7 an electric gas flow meter, 8 combined unit, 9 pressure regulator in the line "to yourself", 10 pneumatic resistance, 11 fitting for the supply of the analyzed gas with an EFA content of more than 100 million ^-1 .

, а затем на контрольную часть $$l_{\stackrel{⌢}{e}}$$

кулонометрической ячейки, в это время напряжение, подаваемое с блока комбинированного 8 на электроды кулонометрической ячейки, одинаковое, и они работают в одном режиме полного поглощения ОДВ, далее анализируемый газ поступает на электронный измеритель расхода газа 7, который определяет своей полярностью выходного сигнала, подаваемого в блок комбинированный, направление движения анализируемого газа, далее анализируемый газ через сопротивление пневматическое 10 поступает на штуцер 11.When measuring the EFA to 100 million ^-1 analyzed gas under pressure is supplied to nozzle 1 hygrometer, air passes through the resistance 2 and split into two streams - the bypass flow and flow through coulometric cell. At the point of separation of the flows, the pressure is maintained constant with the help of a gas pressure stabilizer in the line "to yourself" 3. The dosed gas flow passes through the pneumatic resistance 4, enters the working part $$l_{\partial }$$

and then to the control part $$l_{\stackrel{⌢}{e}}$$

coulometric cell, at this time the voltage supplied from the combined 8 unit to the electrodes of the coulometric cell is the same, and they operate in the same mode of complete absorption of the EFA, then the analyzed gas is fed to the electronic gas flow meter 7, which determines by its polarity the output signal supplied to combined block, the direction of movement of the analyzed gas, then the analyzed gas through the pneumatic resistance 10 is supplied to the fitting 11.

When applying the analyzed gas to the nozzle 1 of the hygrometer, the pressure stabilizer in the line "to yourself" 9 is closed, because pressure at the inlet of the stabilizer is close to atmospheric.

When measured over 100 million EFA ^-1 analyzed pressurized gas supplied to the nozzle 11 hygrometer, air passes through the resistance 10 and is split into two streams - the bypass flow through and the coulometric cell. At the point of separation of the flows, the pressure is maintained constant using the pressure stabilizer in the line "to yourself" 9. The metered flow enters the electronic gas flow meter 7, which changes its polarity of the output signal supplied to the combined unit 8. By changing the polarity of the signal of the electronic gas flow meter in the combined unit, the voltage applied to the electrodes of the coulometric cell will change, with more voltage being applied to the working part and less voltage being applied to the control part. The current increment in the working and control parts of the coulometric cell is determined by the formula 2:

where ΔI is the increment of the current coulometric cell in the area Δx;

U is the voltage applied to the working and control parts of the cell;

q is the coefficient characterizing the geometry of the cell;

σ is the specific conductivity.

In the control part, moisture absorption will be reduced, and in the working part, moisture absorption will be increased. As a result of this, the condition of almost complete absorption of moisture by the coulometric cell will be fulfilled. Due to the fact that the absorption in the control part of the coulometric cell decreases, and, accordingly, the electrolysis current decreases. Therefore, the control part of the coulometric cell will be smaller than the heater, and jumpers between the electrodes will not form, then the analyzed gas through pneumatic resistances 4 and 2 goes to the nozzle 1. When the analyzed gas is fed to the nozzle 11 of the hygrometer, the pressure regulator in the “to itself” line 3 is closed because pressure at the inlet of the stabilizer is close to atmospheric.

Claims (1)

A hygrometer comprising a gas flow forming unit with a coulometric cell, characterized in that, in order to increase the life of the hygrometer, the analyzed gas can be supplied both from the side of the working part and from the control part of the coulometric cell.