SU1656437A1 - Device for measuring ohmic resistances of contact conductometric cells - Google Patents

Abstract

The invention relates to electrical analysis and can be applied to control technological solutions used in the chemical industry. The purpose of the invention is to improve the measurement accuracy of the active component of the resistance of a contact conductometer cell. Improvement of accuracy is achieved due to coverage of the integrators with negative feedback and processing of the measurement result in two steps. The invention relates to electrochemical analysis and can be used to automatically control process solutions in the chemical industry. The purpose of the invention is to improve the measurement accuracy. The drawing shows the functional diagram of the device. The device contains a trigger 1, an inverter 2, two two-input logic circuits AND 3 and 4, a pulse shaper 5, the generation contains a trigger 1, an inverter 2. two two-input logic circuits AND 3, 4. a shaper 5 square-wave pulses, an alternating voltage generator 6 , contact conductometric cell 7. variable active resistance 8. constant active resistance 9, keys 10 and 11, two integrators 12 and 19 pulse shaper of a given duration 17, storage unit 18 About the active component resistance The tact conductometric cell is judged by the value of a variable resistor connected in series with it, the value of which is determined from the condition of equality of the integral values of the voltage drop across this resistance and the cell formed, successively during the first and second half periods of the voltage which is connected in series with a conductometric cell, variable active resistance and alternating voltage generator 1 or torus alternator 6. The second voltage contact conductometric cell 7, the variable resistance 8, a constant resistance 9, the keys 10 and 11, a first integrator 12 comprising scaling resistors 13, 14, 15 (Rn, Ri4. Ris) and an integrating capacitor 16 (Cie) pulse shaper 17, a storage unit 18, a second integrator 19 with a scaling resistor 20 (R2o) and an integrating capacitance 21 (C2i). as well as measuring unit 22. About sl iЈ and

Description

The device works as follows.

From the generator 6 harmonic oscillations receive a sinusoidal alternating voltage of 1L average sound, frequencies

Ur Um sinwr, where Dm is the voltage amplitude;

o 2l f angular frequency voltage;

f is the voltage frequency;

T is the period of oscillation;

t - time

Through the circuit consisting of a series-connected alternating voltage generator 6, a constant active resistance 9, an alternating active resistance 8 and a contact conductometric cell 7 with the electrolyte solution under test, a current flows

Umsln (tur + V).

I

IRi + R2 + Z I I where Ri is the resistance of a constant active resistor 9;

R2 is the resistance of the variable active resistor 8;

2I is the cell impedance with the electrolyte solution under study;

ty is the phase angle between the voltage and current of this circuit.

The voltage drop at a constant active resistance of 9 is equal to

URi-lRi, R mR2R; Za, sln ().

The voltage drop across the variable active resistance is 8

UR2 IR2TWT I7rs.n (Wr).

The voltage drop on the contact conductometric cell 7 with the electrolyte solution under study is equal to

c, t 7Urn

Uz -IZ IRi + R2 + Z, l X

x sin (honeycomb),

where (f is the phase angle between the current through the cell and the voltage drop across it.

At the output of the pulse shaper 5, a periodic rectangular voltage is formed, the phase of which coincides with the voltage drop phase at a constant active resistance 9, and in one half period of the voltage drop at this resistance at the output of the pulse shaper 5 a signal equal to logical 1 is formed, and in the other half period of this voltage drop - a logical signal

0. These are periodic voltages supplied to the counting input of the trigger 1. which divides the frequency of the voltage input to its counting input by 2. In this case, the direct

trigger output 1 there is a periodic rectangular voltage whose half-period duration is equal to the period of the voltage received at its input

When the forward output of the trigger 1 through 0 is a voltage equal to the logic 1 and the output of the pulse generator 5 also has a signal from the logical 1, the output of the logic circuit 4 has a signal 1 which opens

5 key 11. At the same time, the first inverting input of the first integrator receives a voltage drop from the variable active resistor 8. The integration limits are determined by the duration of one half of the voltage drop across the constant active resistance 9 when the key is open 11. The output voltage of the first integrator at the time of closing the key 11 is equal to

5U n-ljHHT.i

   x

RnCi6, /, I Ri + R2 + Z “I

x sin (pcs

0

five

0

five

0

five

 -21

V y) d t t UmR2

Rl3Ci6 I Ri + R2 + Z “I

At the end of each half-period of the voltage drop with a constant active resistance 9 of the pulse shaper 17, an output short-term impulse of a predetermined duration is obtained, which is fed to the control input of the storage cell 18. And the content of my first integrator 12 at the end of the first half-period of the voltage drop is constant The active resistance 9 is recorded in block 18.

In the other half-period of the voltage drop across the active constant resistance 9 at the direct output, about the trigger 1 there is also a logical 1 signal, and at the output of the pulse driver 5 a logical 0 signal appears. Since the output of the pulse shaper 5 is connected to the first input of the logical And 3 through the inverter 2, and its other input receives a signal from the direct output of flip-flop 1, the output of the logic circuit And 3 in the second half-period of the voltage drop across the active resistance 9 appears a logical signal 1, which opens the key 10. When this The first inverting input of the first integrator 12 is connected to the conductometric cell 7, therefore during the other half period

the voltage drop across the active resistance 9, while the switch 10 is open, the voltage is integrated across the conductometric cell. At the same time, the second inverting input of the first integratooa 12 receives a signal from the output of the storage unit 18, and the third inverting input receives the voltage from the second integrator 19. As a result of integrating these three voltages, the first integrator 12 is the voltage at the output of the second half period of the voltage at its output.

U nlHHT 1 1

i. L - U :, 7

 Ig Um -

  n i

x sin ((i) T + t / -9) d tor, 2 JT -; /,

Um

 - JU | n 1

K; 4 Yb d - /

x d о t - -k-V- x Ri5 Ci6

ъ - X

From C21

2I - gr

X id (Fri} d (FROM

- p Under the condition

one

Rl4 Cie 1

get

X

one

COS F 5pr-X

 Ricia

x

--4R2 Z, cosp).

I Ri + R2 4- Za I

At the end of the second cycle, the pulse shaper 17 of a given dpness generates again the signal to the control input of the storage unit 18 and the contents of the first integrator is stored by this unit. In this case, the output voltage of the unit 18 is controlled by the measuring unit 22. By changing the value of the variable resistance 8, the amplitude of this voltage is equal to zero. This happens if the ratio

Ri3 Cie ..2 Um

X

I Ri + R2 + ZBI

(R2 - 2Y cos /) 0

or R2 is ZflCosy 0.

Since Z "cos f Rq, then the equality of 10 voltage from block 18 will be in the event that the relation R2 R"

From this equation, it can be seen that if the cell resistance is measured in terms of the resistance value of the variable resistor 8, the measurement result, if the conditions discussed above are met, will be free from the effect of the reactive component. 20

Claims (1)

Invention Formula Device for measuring the active component of the contact resistance 25 a conductometric cell containing a measuring unit, an alternating voltage generator, the first output of which is connected to the first terminal for connecting the conductometric cell and the information input of the first switch, the second output of the alternating voltage generator through series-connected constant and variable active resistance connected to the second terminal to connect 35 of the conductometric cell and the common bus, the second outputs of the constant and variable active resistances are connected to the information input of the second key and the first input of the first driver with 40 pulses, the outputs of the first and second keys are connected to the first input of the first integrator, the control inputs of the first and second keys are connected to the outputs, respectively, of the first and second elements I, the first input of the first element I is NOT connected to the first input of the second element I through the element, the output of the first pulse generator and in Trigger house direct output of which is connected with the second 50 inputs of the first and second elements I. In this case, the second input of the first pulse generator is connected to the second output of the alternating voltage generator, characterized in that, in order to increase 55 of the measurement accuracy, a memory block, a second integrator and a second pulse shaper are inputted into it, the input of which is connected to the output of the first pulse shaper, and the output is connected to the control input of the memory block, the information input of which is connected to the output of the first integrator, the output of the storage unit is connected to the input of the second integrator, the output of which is connected to the second input of the first integrator, while the measuring unit is connected between the output of the storage unit and the third input of the first integrator. t: j