SU819746A2 - Resistance to frequency time signal converter - Google Patents

Description

one

The invention relates to electrical measuring technology and can be used in frequency-digital measuring devices operating from resistive sensors, such as potentiometric sensors, strain gauges and resistance thermometers.

The closest technical solution to the invention is a transducer of resistance to a time-frequency signal according to the main auth. No. 470919, containing an operational amplifier with a differentiating QS negative-feedback circuit (integrator), a comparator unit, a two-position current switch, two different polarity measuring current regulators, and a sample resistor l. However, in the case when the initial value of the transformed impedance is not zero, it is impossible in principle to obtain an initial output frequency equal to zero.

The aim of the invention is to extend the functionality of the generator of the generator by obtaining the initial output frequency equal to zero, with the initial value of the transformed resistance equal to zero.

This is achieved by the fact that in the impedance converter there is a frequency-time signal containing an operational amplifier with a negative feedback differentiating RC circuit, the output of which is connected to one of the inputs of the reference unit, two

0 opposite current regulator with two-point current switch, exemplary resistor, output of two-position current switch connected to the second input of the comparator unit and to the divider from the reference resistor

5 and a convertible resistor, with the middle point of the divider connected to the non-inverting input of the operational amplifier, the output of the block

0 Comparison of the connection to the control input of a two-position current switch, phase inverter introduced, compensating resistor, two compensating stabilizers

5 current, an additional two-point current switch, the inverter's input of the inverter is connected to the output of the comparator unit, and the output to the control (INPUT -additional two-position key of which two inputs are connected to the outputs of two equal-polarized compensation current stabilizers, and the output to the first output of the compensating resistor and to the output of the transforming resistor, the second output of the compensating resistor is connected to the housing (ground).

The drawing shows the functional diagram of the Converter.

The converter contains an operational amplifier 1, a differentiated RC feedback negative feedback 2, a comparison unit 3.

Two-point current switch 4, different polarity measuring current stabilizers 5 and b, exemplary resistor 7, convertible resistor 8, additional two-position current switch 9, different polarity compensation current compensators 10 and 11, compensating resistor 12, phase inverter 13.

The converter operates as follows. A two-position current switch 4, controlled by a multi-polar voltage from the output of the comparator unit 3, alternately connects one of the measuring current stabilizers 5 and 6 to the divider of resistors 7, 8 and 12. An additional on-off current switch 9, controlled by the alternating voltage from the output of the phase inverter 13, alternately connects one of the compensation current regulators 10 and 11 to the compensating resistor 12. Since the voltage at the output of the comparison unit 3 and at the output of the phase inverter 13 is at any time time opposite in sign, the measuring current flowing through the compensating resistor 12, at any time directed towards the compensation current flowing through the same resistor 12. This leads to y that the voltage due to the flow of the compensation current through the compensating resistor 12 is subtracted from the voltage due to the flow of the measuring current through the transformed resistor 8 and KOM-I reaming resistor 12. The difference between these voltages is fed to the input of the operational amplifier 1 and further work the converter does not differ from the operation of the converter according to the autor. No. 470919. If the voltage due to the flow of the measuring current through the resistors 8 and 12 is equal to the voltage due to the flow of the compensation current through the resistor 12, then the voltage at the input of the operational amplifier 1 is zero and there is no oscillation at the output of the converter (i.e. output frequency is zero).

Since the period of voltage oscillations at the output of the converter

contains two equal in duration and amplitude, but opposite in magnitude of the voltage half-period, and knowing that the switchings of the direction of integration occurring through each aoluperiod are made with equal voltages at the inputs of the unit of comparison 3, you can write

| olVRKb RKl 2 aolRx R V3 R

2 Зо1Кх “о к1-3 к, Н)

where o is the time constant of opamp 1 with a differential feedback circuit of negative feedback 2}

R is the value of the measuring current of the stabilizer 5 and 6;

, RX is the value of the transformed resistor .8}

RK - compensating value

resistor 12}

3 - the value of the compensation current stabilizers 10 and

eleven; .

-y the length of the semi-period of the output oscillation of the converter;

Rg is the value of the reference resistor 7.

Hence the period of the output oscillation of the converter

4 o: ioR

T

3otRx + R "V3" u "

and the output frequency of the converter

: iolRx + RRVDKR K

i

4 tloRo

out

From the formula (3) it can be seen that the output frequency depends linearly on the resistor 8 being converted. Denoting the З / ЗОЕ ratio, (. 1) and entering it into the output frequency formula, we get

i

Bbix-.lRx Rtt-eRK) W

This shows that

ABOUT

with ER RX + RK,

zyh

from which it can be concluded that to obtain the initial output frequency: converter transducer equal to y, with the initial value of the transformed resistor 8. not equal to zero, it is necessary to choose the value of the compensating resistor 12 from the condition

Claims (1)

where RXH is the initial value of the transformable resistor 8. The use of this converter in the set of remote digital parameter measurement equipment, such as temperature, has greatly simplified the reading digital device, since in this case it is not necessary to subtract the initial frequency corresponding to it. In addition, shifting the output frequency range of the inverter to the lower one, starting from zero, allows a significant increase in the pulse duration, which, in turn, significantly increases the distance between the converter and the readout device without increasing measurement errors, since Distributed capacitance and inductance of the line affects at lower frequencies and for longer durations of pulses is much shorter. Claims of the Invention: Resistance Converter to a Time-Frequency Signal according to auth.St. No. 470919, characterized in that, in order to expand the functionality of the converter, a phase inverter, a compensating resistor, two different polarity compensation current regulators, an additional two-position current switch, are introduced, the phase inverter input is connected to the output of the reference unit, and the output is connected to the control input additional two-position current switch, two inputs of which are connected to the outputs of two different polarity compensation current regulators, and the output - to the first output of the compensating resistor and to the output of the transformed resistor, the second output of the compensating resistor is connected to the housing (ground). , Sources of information taken into account during the examination 1. USSR author's certificate No. 470919, cl. N. OZ K 13/20, 1971 (prototype).