SU1434347A1 - Method of measuring gas concentration - Google Patents

Abstract

The invention relates to a gas analysis technique, in particular, to devices of a conductometric compensation type, and can be used in the metallurgical, chemical and other areas of the national economy. The purpose of the invention is to increase the measurement performance while improving metrological characteristics. In this autocompensation bridge meter with a working and compensating sensitive element, the resistance of the working sensitive element is preliminarily measured, a constant shunt resistance is established, based on the measured value, the variable component is found, based on the compensation of the temperature error and the upper limit of measurement, and starting from the found resistance values of the working sensitive element, the variable and constant components of the resistance {a (shunt, o thinned out incremental resistance value. 3 yl. (A

Description

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The invention relates to gas analytical methods used in industry for controlling contents. zhany various gases of the production atmosphere and for automation - i technological processes.

The aim of the invention is to increase the measurement performance.

FIG. 1 shows a diagram of the device implementing the method; in fig. 2 ,, 3 - monograms of q / p mode from the arguments R ,,, R, .e R

U

s

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The method is implemented as follows.

Before supplying the test gas, the resistance of the working sensing element is measured. A constant shunt resistance is selected, which is chosen equal to the measured resistance value

An additional 6 and a variable 8 resistance are included in the counter, i.e. when the shaft of the reversing motor 9 is rotated, for example, to the left (right), the resistance of the variable part 8 of the shunt increases (decreases), and the incremental resistance 6 decreases (increases),

The circuit is configured so that in the absence of a signal at the output of the bridge circuit, the additional resistance 6 is completely output, t, e. equal to zero, and the variable part of the shunt 8 is fully entered. In this case, Kdo, 0, and from the equilibrium condition of the bridge, it follows that the voltage in the measuring diagonal of the bridge is absent

0

RI

R

Ru

R w

Rh

RM

to sh

..

(ABOUT

sh

ground pin

Ru,

R ... According to a predetermined calibration dependence (Fig. 2), the value of the variable component of the shunt resistance is found, corresponding to the compensation of the temperature error at the upper limit of the measurement, defined by its parameter q / p (q is the thermal softening, p is the power of converters 30). The value of the additional resistance is determined from the previously obtained nomogram, based on the found resistance values of the sensing element R and the constant component of the shunt resistance (Fig. 3). Then the analyzed gas is supplied and the measurement is made in the autocompensation mode by changing the incremental resistance and shunt resistance. The gas concentration is determined from changes in the value of the additional resistance and the resistance of the shunt.

FIG. 1 is a schematic diagram of a device implementing the method.

40

45

The device contains working 1 and compensating 2 sensitive elements included in the shoulders of the bridge containing 50 holding resistance 3, zero corrector 4, voltage source 5, alternating resistance 6, shunting resistance consisting of constant resistance 7 and alternating 8.55 reversible motor 9, amplifier 10, shunting resistance 11 of the compensation sensing element.

50

0

five

where RH and R | i is the resistance of measuring and compensating sensitive elements;

R, is shunt resistance. When the temperature of the measuring converter rises during gas measurement, its resistance increases, which leads to a decrease in the unbalance signal of the bridge, and the engine 9 at the output of the amplifier 10 begins to reduce the resistance of the variable part of the shunt 8 to such an ARy value that the resistance of the measuring converter 1 and, accordingly, his temperature remained the same. Since the equivalent resistance of the parallel-connected measuring transducer 1 and the resistances of the shunt 7 and 8 is less than the initial value, in order to maintain the current value, the supply of both transducers must be added to the additional resistance

R

Ext

to remain equal to RU

5jL.LA5tf

RM + & R

+ R

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(2)

Obviously, the measure of the conversion of the measured value in this case is the position of the revers- ing shaft. sive engine 9 or the value of additional resistance (Kd) 6 and the variable part of the shunt (uRy),

Claims (1)

Invention Formula The method of determining the gas concentration using an autocompensation bridge containing a working and compensating sensitive elements with an added resistance and shunt resistance in the working sensitive element circuit, which consists in that the initial values of the additional resistance and shunt resistance are set before the measurement, the measurement is made in the autocompensation mode by changing the additional resistance and resistance of the shunt and by changing their values dissolved concentration, characterized in that, with Fiá.1 In order to improve the measurement performance, the resistance of the working sensing element is preliminarily measured, the constant resistance of the shunt is set equal to the found resistance value of the sensitive element, the predetermined calibration dependence determines the value of the variable shunt resistance component corresponding to the compensation of the temperature error at the upper limit of measurement, and determine the initial setting value of the additional resistance, based on the the values of the resistance of the working sensing element, the variable and constant components of the resistance of the shunt. lksh / rh About 12 Kffoff // fff 008 OOif Z S Fut.J Ksh / Ki 3 0.20, j / p 2