SU1522119A1 - Digital meter of resistnace - Google Patents

Abstract

This invention relates to a measurement technique and can be used to measure resistances or their relationships. The purpose of the invention is to improve accuracy. The meter contains sensor 1, voltage source 2, amplifiers 3 and 4, analog-to-digital converter 8. Introduction of capacitors 5 and 6 and switch 7 to the meter eliminated the result of the measurement error caused by the zero offset of amplifiers 3 and 4. 2 or .

Description

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This invention relates to a measurement technique and can be used to measure resistances and their ratios.

The purpose of the invention is to improve the measurement accuracy.

FIG. 1 shows a block diagram of a digital resistance meter; in fig. 2 - time diagrams of signals explaining its operation.

The device contains a sensor 1, a source of reference voltage 2, the first 3 and second 4 amplifiers, the first 5 and second 6 capacitors, switch 7 and the analog-to-digital converter (AIJJ1) 8.

Sensor 1 consists of measured 9 and reference 10 resistances. The outputs of source 2 are connected to the inputs of sensor 1, the outputs of which are connected to the inputs of amplifiers 3 and 4, the output of amplifier 3 is connected via capacitor 5 with a normally lockable output of switch 7 and the signal input of ADC 8, the output of amplifier 4 is connected through capacitor 6 with a normal pa3OMKHyTbiivi output the switch 7 and with the reference input AShch1 V, the clock output 8 is connected to the control inputs of the source 2 and the switch 7, the middle contact of which is connected to the common bus.

The meter works as follows.

The source 2 produces at its output an alternating rectangular voltage (Fig. 2a), synchronous with the output voltage of the A / D converter 8 (Fig. 2b) and having an amplitude U. This voltage is converted by sensor 1 and amplifiers 3 and 4 3 into two rectangular voltages (phi1. 2c, d), the amplitudes of which

are equal:

RO

,to

. + Rn

(12)

where RX is the resistance of the measured

a resistor;

RO is the resistance of the reference resistor;

 - gains of amplifiers 3 and 4, respectively. The alternating voltage from the output of amplifier 3, the passage through capacitor 5, is converted into negative pulses by amplitude. 2U (Fig. 2e), and the voltage from the output of amplifier 4, the passage through capacitor 6, is converted into positive pulses with an amplitude of 2U2 (Fig. 2e). A1Shch 8, which can be built on the principle of double integration, produces at its digital output a code proportional to the ratio 2U to

0

five

0

0

five

0

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Since the inputs to the ADC 8 are supplied with voltage, which corresponds in magnitude to the magnitude of the voltages at the outputs of amplifiers 3 and 4, there are no errors in the code caused by the offset. zero voltage of these amplifiers.

Claims (1)

Invention Formula A digital resistance meter containing a source of a reference voltage, or a resistance sensor connected in series with an analog-to-digital converter, the first and second differential amplifiers, whose inputs are connected to the outputs of the resistance sensor, characterized in that, in order to improve the measurement accuracy, A switch and two capacitors are inserted, the middle contact of the switch is connected to the common bus, the normally closed contact of the switch is connected to the first output of the first capacitor and the signal With an analog-digital converter input, a normally open contact of the switch is connected to the first output of the second capacitor and a reference input of the analog-digital converter, the synchronizing output of which is connected to the control inputs of the reference voltage source and switch, the second terminals of the first and second capacitors are connected to the outputs the first and second differential amplifiers, respectively. ig.2