SU1541527A1 - Method of measuring conduction of media - Google Patents

Abstract

The invention relates to the field of electrical measurements, in particular to the measurement of parameters of media by resonant methods. The aim of the invention is to improve the accuracy. The method for measuring electrical conductivity consists in exciting an oscillating circuit, which includes a measuring cell, with type β-function pulses at two natural frequencies ω ₁ and ω _{2 of the} oscillating circuit, cycles, the reaction signals of the circuit are detected and integrated, and the number of excitation cycles N ₁ at the frequency ω ₁ and the number of cycles N ₂ at the frequency ω ₂ are chosen from the condition of equality of the integrals of the corresponding detected response signals of the circuit to the excitation, based on the change in the quality factor of the circuit, determine the conductivity l environment. The goal is achieved by driving pulses at two eigenfrequencies of the circuit with cycles, desektirovaniya and integrating the reaction signals of the circuit and the appropriate choice of the number of cycles of the circuit excitation at two frequencies. 1 il.

Description

The invention relates to electrical measurements, in particular, to measuring the conductivity of media.

The aim of the invention is to improve the accuracy,

The drawing shows a device that implements the proposed method.

The essence of the method is as follows.

In the LC circuit, in which the measuring transducer is included, free damped oscillations are excited by affecting it with a short rectangular pulse, the model of which serves the cf-function.

In an operational form, the reaction contour Us (p) has the form

Z (p) R + Lp + Ig;

«« ZfSi-ityEb-TTpt

 - (n TЈ-G7rs7 ё

Accept

cl

SL

u-j

R

2E

 wX (p)

of

(2)

p + 2 ar + i) 7

During the transition to the temporary region, the voltage on the circuit is

L -S,

-oit

 ,

(3)

Where

s, v

We take into account that already at Q 5 and), differs from .co by 0.5%, rewritten (3) in the form

lf (t) sinu), t. (four)

Further, the voltage on the circuit, having the form (4), is detected and integrated by the analog integrator. Express voltage at integrator output

 T

K „i

their

soy / sinu t / dt (5)

Where

Kipostnna time integrator 20 ra.

To simplify the integration operation, the integrand can be expanded in Fourier series

. . 25

+ T5 24 OTA; t7 + where T is a constant oscillator-35 time

new contour.

Analysis of expression (7). shows that the sum of the terms of the series, starting with the second, in a wide range of Q-factors Q (from units and above) is several orders of magnitude less than the first term of the series. Therefore, the voltage at the output of the integrator can be represented with a high degree of accuracy.

Au

U

Int

 TR; w T

(eight)

because

About YT C 2

U

icht ig Q

(9)

From the expression (8) it can be seen that the signal at the integrator output is proportional to the quality factor of the excited oscillatory circuit.

Conducted a measurement of Q at two frequencies and), and, the desired be0

s

0

five

0

35

40 b is determined from the relation Q, (w ,, 6) / Q7 (tjf, 6).

A device that implements the proposed method contains an excitation unit 1, an oscillating circuit 2, which includes a measuring sensor, a buffer amplifier 3, a controlled amplifier-detector 4, an integrator 5, a comparator 6, a frequency generator 7, a driver 8 of control signals , block AND 9, block OR 10.

The output of the generator 7 reference frequency is connected to the input unit

1, the output of which is connected to the oscillatory circuit 2 connected to the input of the buffer amplifier

3, the output of which is connected to the input of the controlled amplifier-detector 4, the output of which is connected to the input of the integrator 5, the output of which is connected to the first input of the comparator 6, to the second input of which the reference voltage Uon is applied, and the output to the first input of the AND 9 block and the third output of the control signal generator 8, the second input of the AND block 9 is connected to the output of the OR block 10, the first input of which is connected to the output of the clock generator 7, and the first input of the control signal generator 8, and the second input of the first control signal generator 8 laziness and oscillating circuit control inputs

2 and amplifier-detector 4, the second output of the driver 8 of the control signals is connected to the control input of the integrator 5, and a Start signal is applied to its second input.

The device works as follows.

The reference frequency generator 7 generates pulses that trigger the excitation unit 1, and clocks the operation of the control signal generator 8. With the arrival of the signal, the start starts the first cycle of the conversion. Uk damped oscillations from contour 2

The sensor includes a measuring sensor, through a buffer amplifier 3 is fed to a controlled amplifier-detector 4 (at the output of which, depending on the control signal, a detected voltage of positive or negative polarity can be obtained, which is controlled from the driver 8 control signals. Integration

the voltage received is carried out by an analog integrator 5. Exceeding an initoporno level (which may be zero) causes an interrupt of comparator 6, starts the counting of start pulses, when their number reaches 0 and the second conversion cycle begins. The integrator starts working on subtraction, and pulses from the reference frequency generator begin to flow to the device output. This process is continued.

3 About b p

et e and

The method of measuring the conductivity of the media, which consists in exciting an oscillating circuit, which includes a measuring cell, and judging by the change in the quality of the circuit, the conductivity of the medium is judged, characterized in that, in order to improve the accuracy, the circuit is excited by f-type pulses, moreover, the excitation is carried out at two natural frequencies of the oscillatory

Before comparing ipmg to Uen Co-contour s, and oh, the excitation conducts a number of pulses at the output will turn out to be 15 with equal N.

. № $

At the end of the second conversion cycle, the device is reset.

with cycles, the contour response signals are detected and integrated, the number of excitation cycles Nt at the frequency C, and the number of excitation cycles at the frequency are selected from the condition that the integrals of the corresponding detected contour response to excitation are equal.

5th Formulas

6

3 About b p

et e and

The method of measuring the conductivity of the media, which consists in exciting an oscillating circuit, which includes a measuring cell, and judging by the change in the quality of the circuit, the conductivity of the medium is judged, characterized in that, in order to improve the accuracy, the circuit is excited by f-type pulses, moreover, the excitation is carried out at two natural frequencies of the oscillatory

contour s, and oh, arousal conducts contour s, and oh, arousal conducts

with cycles, the contour response signals are detected and integrated, the number of excitation cycles Nt at the frequency C, and the number of excitation cycles at the frequency are selected from the condition that the integrals of the corresponding detected contour response to excitation are equal.

Claims (1)

Claim The method of measuring the conductivity of the media, namely, that they excite the oscillatory circuit, which includes a measuring cell, and by changing the quality factor of the circuit they judge the conductivity of the medium, characterized in that, in order to improve accuracy, the circuit is excited by pulses of the <f-function type, moreover, the excitation is carried out at two natural frequencies of the oscillatory circuit and the excitation is carried out by cycles, the reaction signals of the circuit are detected and integrated, while the number of cycles of excitation of the HZ at a frequency s, and the number of cycles of excitation The phenomena at the frequency o ^ are selected from the condition that the integrals of the corresponding detected signals of the circuit response to excitation are equal.