SU1624351A1 - Device for resistance checking and measurement - Google Patents

Abstract

The invention relates to a measurement technique and is intended to monitor and measure resistances. The purpose of the invention is to enhance the functionality and increase speed. A low voltage level in the resistance control mode closes the keys 3 and 4. At the output of the digital-to-analog converter 10, a voltage appears proportional to the voltage coming from the output of the adjustable source 14 of the reference voltage. On the reversible counter 1

Description

The invention relates to a measuring technique and is intended for controp and measurement of active resistances in automated control systems.

The aim of the invention is to enhance the functionality and improve performance.

FIG. 1 shows a functional diagram of a device for monitoring and and resistor resistance; FIG. 2 — a variant of replenishment of a regulated source of voltage.

A device for monitoring and measuring resistance includes reversing. the counter 1 with the output bus 2 and g (; its input of the prerecording of the number bx (f), which is the code of the permissible value of the monitored resistance Ign1) is the setpoint code, the third trigger g versus counter 1 is the third internal memory of the device. Counter 1 has a fourth input, input C - the third input of the device intended to control the recording of the number Nxf) The first and second counting inputs of h and - counter 1, corresponding to forward and reverse counting, are connected to the outputs of keys 3 and A The first inputs of keys 3 and 4 are connected with device input The second inputs of the keys 3 and 4 are connected respectively to the output of the first comparator 5 and the output of the inverter 6. The output of the comparator 5 is also the second output of the device for monitoring and measuring resistances, the first and second inputs of the comparator 5 are connected respectively to the outputs of the amplifiers 7 and 8. The output of the counter 1 is connected to the first output of the device for monitoring and measuring resistances and the first (digital) input of the DAC 9. The amplifier 8 is connected to the output of the DAC 10, the first input of which is connected to the second input of the device Outputs of the DAC 9. 10 are connected with the second and first inputs of the adder 11. the output of which is connected to the first

the input of the comparator 12, the second input of which is connected to the second output of the divider 13, the output of the comparator 12 is connected to the input of the adjustable source 14 of the reference

nzpo marriage. Source 14 may be either in the form of an integrator 15, or (FIG. 2) in the form of a DAC 16, the output of which is the “input of source 14. This input is connected to the input of the reversing counter 17, the inputs

the forward and reverse counting of which are connected respectively to the outputs of the keys 18 and 19 of the first time whose inputs are connected to a pulse signal, and the second inputs of which are connected respectively to the inverter 20 output and output. It controls the source 14 14 is connected to the second inputs (reference voltage reference voltage) of the D / A converters 9 and 10.

And: power supply (U) measuring

the circuit with one pole is connected to the common bus, the other (positive) to the first output of the splitter 13 and the first terminal for connecting the test resistance 21 (Rx),

representing the input of amplifier 7, the RTG terminal for connecting which is SEDINED (E with the first terminal of the limiting resistor 22 (R0), the second terminal of the resistor 22 is connected to the input of the operational amplifier 23 and the common point of two series-connected limiting diodes 24 and 25. connected to the positive power supply bus (Uni) opamp

B23, RNOD of G4 diode 24 is connected to the negative gate of the power supply (Un2) of the operational / silicon 23. The resistor 26 (Ro) in the reverse link of the operational amplifier 23 has a resistance equal to that of the limiting resistor 22. The third divider 13 is connected to common bus. Deplit 13 contains RtnRa resistors.

The device for monitoring and measuring the resistance works as follows.

In the control mode, a low voltage level is applied to the first input (input 1) of the device, which closes the keys 3 and 4. The second input (input 2) of the device is given the code No. corresponding to the resistance Ro of resistor 22 in the feedback circuit of opamp 23.

Since the resistor Ro can have a constant value for a large range of monitored resistances R. Then, N0 is also a constant number. In this case, the bits of the first input of the DAC 10. corresponding to the KSDR No. connect to the common bus, the bits corresponding to 1, to level 1. At the output of the D / A converter 10, the voltage U0 appears

the output of the comparator 12, the voltage UK becomes positive, therefore, at the output of the integrator 15, the voltage U0n begins to decrease linearly. Therefore, it will decrease - this follows from (3) - the voltage Uz, until the voltages Ux are not equalized. Therefore ie Uz. from (3) and (4)

ten

U

R2 and No -I-Nxd (. RTTR2 e

15

NEADU; -z (if) and substituting it in (1), we get

Do

Nc

Uc

ABOUT)

where m is the number of bits of the DAC;

Don is the voltage supplied to the second (reference voltage supply) input (input I) of the DAC 10 from the output of source 14.

At the third input (input 3) of the counter 1, the code of the allowed value of the monitored resistance Rx is set. After that, a write pulse is applied to the fourth input (input 4) of the device (second input C of counter 1). At the output of counter 1, an Nx code is set, which acts on the input of the DAC 9.

At the output of the D / A converter 9, the voltage Ux3 is set.

n Nx (3.i

Uxau on

from

(2)

At the output of the adder 11 there is a voltage U,

Uc

UE U0 + Uv3 - (No f Nxd). (3)

r GP

The voltage Us is supplied to the first input of the comparator 12, the second input of the comparator 12 receives the voltage from the second output of the divider 13

U L U -

R2

Rl + R2

(four)

At the inputs of the comparator 12, voltage is maintained with high accuracy and Uj. using negative feedback through source 14, D / A 9 and 10, and adder 11.

So, if for some reason, Us decreases, and hence id. then on

I - I (C

Uo and ™ -. (about;

2 The voltage Ux at the output of the operational amplifier 23 is determined by the form.

Ux and ..-

RC + RX

00

At the output of the amplifier 8, there is an AC voltage.

. (eight)

If we take into account that the code N0 accurately reflects R0, then the case of R / - NX is not the input of the cooperator 5. This means that the voltage at the second output of the device is 0, with

Rx NX3. Uebixi 0, with Rx Nx3, and output2 0. (9)

From the analysis of (7) and (9) it follows that the control error does not depend on the change in the supply voltage of the measuring circuit, the device allows setting the permissible values of the controlled resistance directly in the resistance codes, n the measuring circuit of the proposed device, all effective current, i.e. the current carrying information about the monitored value is used for further amplification.

The introduction of the limiting resistor 22 (Ro) in conjunction with the diodes 24, 25 protects the input circuit of the operational amplifier 23 when large U is used, and due to the defect Rx 0, but the choice

equal values of 22 (R0) in the limiting circuit and in the feedback circuit allows one to obtain such a transfer function at which it is possible to set the setpoint in units of a controlled quantity, i.e. / nsynuyu dependence of the setting of the controlled value.

Consider the operation of the device for monitoring and measuring the resistance in the measurement mode. For this mode, the first input (input 1) of the device is connected to the bus of the source of pulses that follow continuously.

The second input (input 2) of the device is connected, as in the monitoring mode, the third and fourth inputs (inputs 3 and 4 of the device) are not used. At the first output (output 1) of the device, remove the Nx code of the measured resistance (Rx).

In the measurement mode, the device for monitoring and measuring the resistance operates as a dual-circuit tracking system. The equilibration of the pertz contour occurs on the comparator 12 in the same way as in the control mode.

Balancing of the second circuit occurs at comparator 5 by changing the contents of counter 1. If at some point Ux Uc. then the output of the comparator 5 will be 1, the output of the inverter 6 O. The key 4 is closed, the key 3 is open, the pulses are passed to the second (+) (direct) counting input, the contents of counter 1 are increased. The voltage Uxd at the output of the DAC 9 increases, ug increases, UK2 - the voltage at the output of the comparator 12 becomes positive. The voltage Don at the output of source 14 decreases, Uo decreases at the output of DAC 10, Uc increases at the output of amplifier 8, and the device for monitoring and measuring resistances approaches equilibrium when Ux Uc.

If at some point Ux Uc turns out, then key 3 is closed by signal O from the output of comparator 5, key 4 is opened, counter 1 counts in the opposite direction, ehz and Uj decrease, UKZ becomes negative, Uon increases, Uo increases, Uc decreases . A device for monitoring and measuring resistance approaches equilibrium.

Balancing of both contours occurs in parallel in time.

Let us show that there is an equilibrium state for the device for monitoring and measuring the resistances and for a certain constant RX connected to the measuring circuit. At the same time, RX N.

Due to negative feedback, both circuits come to equilibrium, when

Ux-Uc, ui ee. (Yu)

(7) and (8) are also valid for the measurement mode.

For the measurement mode in formulas (2), (3), (5), (6), (9) instead of Ndx, which was unchanged at the output of counter 1 and at the input of the DAC 9, the current content of counter 1 should be substituted.

At the moment when Ux Uc, in view of (7) and (9), we have

U

Re

Ro + R,

 U

Nc

No + nx

R

whence rx nx -.

N °

If Ro is N0, then Rx NX. Thus, the measurement mode after equilibration at the output 1 of the device for monitoring and measuring the resistances is the code Nx, which reflects the measured resistance Rx.

The operation of the device for monitoring and measuring the resistance is described for the case when the source 14 of the reference voltage is designed as an integrator 15. In the case of a source based on the DAC (Fig. 2), the operation proceeds as follows. The signal IR2 from the output of the comparator 12 is low O or high 1. The second inputs of the keys 18 and 19 are always connected to

pulse source bus. On the first zho

The keys of the 1S and 19 keys always receive mutually inverse signals, so one key transmits pulses, and the other produces a constant level 1.

If Uz Ud, then Uic2 1, and impulses

via key 18 is fed to the input of the direct count of the reversible counter 17, from which the signal goes to the input of the DAC 16, from the output of the latter, the signal Uon is fed to the output of the source 14 of the reference voltage, and Uon increases, as in the case of the use of the integrator.

If Unu, then Uic2 O, the key 19 is open, the countdown is in progress, U0n decreases.

The transmission coefficients of the divider 13 and the operational amplifier 23 are chosen in such a way that their product is equal to one.

Combining the monitoring and measuring functions in one device allows extending the functionality and speeding up, since a time gain will be achieved in comparison with the known devices, in which the tested resistances are measured, and then, according to the measurement results, the decision is made in norm or not. norm

Claims (1)

Claims An apparatus for monitoring and measuring resistances, comprising a series-connected reversible counter and a first digital-to-analog converter, a first comparator, a first amplifier, first and second keys, and outputs of the first vi of the second keys are connected respectively to the first and second counting inputs of the reversible counter the first output of the device, characterized in that, with the aim of expanding the functionality and speeding up, A second digital-to-analog converter and a second amplifier, a series-connected adder, a second comparator and an adjustable voltage source, an inverter and a divider, the first terminal of which is connected to the positive power supply busbar and the first terminal for connecting the test object, the second terminal for connecting connected to the input of the first amplifier, the output of which The first comparator is connected to the input of the inverter, the second input of the first comparator is connected to the input of the second amplifier, the first input of the device is connected to the first inputs of the first and second keys, the second input of the first switch is connected to the output of the first comparator and the output of the device, the second input of the software device KPYUCHRN to the first input of the second L ifpo: n9logovogo converter, the third and fourth inputs of the device are connected to the third and fourth inputs, respectively, of the roar of the rsiv counter, the output of the adjustable voltage source is connected to the second inputs of the first and second digital-to-phono converter; the output of the second digital-analog converter is connected to the first input of the adder, the second input of which is connected to the output of the first digital-analog converter, to the second output of the divider, whose iGenade is degenerated to the common bus. ig. 2