SU1675795A1 - Device for measuring resistance increment - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure small changes in resistance. The aim of the invention is to improve the speed without reducing the measurement accuracy. The device contains reference voltage source 1, current stabilizing element 2, resistive sensor 3, output terminals 4, operational amplifier 5, comparator 6, RS-trigger 8, voltage storage unit 7, element 9, counter 10, digital-analog converter 11 and the clock generator 12. 3 Il.

Description

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The invention relates to a measurement technique and can be used to measure small increments of resistors.

The aim of the invention is to improve the speed of the device without degrading the measurement accuracy.

FIG. 1 shows a functional diagram of the device; in fig. 2 is a voltage change diagram of the non-inverting input of the op amp; in fig. 3 is a voltage change diagram at the output of the device.

The device contains a source of reference voltage 1, a current stabilizing element 2, a resistive sensor 3, an output terminal 4, an operational amplifier 5, a comparator 6, a voltage storage unit 7 including an RS flip-flop 8, an AND 9 element, a counter 10, a digital-to-analog converter 11 and clock generator 12.

The device works as follows.

At the initial moment of time, the output potential of the RS flip-flop 8 and the outputs of the counter 10 are set to low potential, and the output of the converter 11 is the potential of the common bus, therefore the non-inverting input of the operational amplifier 5 and due to deep negative feedback will also be set on its inverting input common bus potential (Fig. 2, interval to - ti). Current

lo ko uo.

where Ko is the transfer coefficient of the current-stabilizing element 2;

Uo is the voltage source 1 of the reference voltage,

creates a voltage drop on the resistive sensor 3 (Fig. 3, the interval to - ti)

UR ° lo Rx °,

where Rx ° is the initial resistance of the resistive sensor 3, which also acts on the first input of the comparator 6, maintaining a logic zero level at its output.

At the moment of time ti, a trigger pulse from the input terminal of the RS-flip-flop 8 sets the - at the entrance to the unit state. In this case, the pulses from the clock generator 12 are fed through the element AND 9 to the input of the counter 10, the output code of which starts to change from zero to a value at which the linear-increasing step voltage at the output of the digital-to-analog converters, thereby

on the inverting input of the operational amplifier 5, will not become equal (Fig. 2, the interval t2 - ti). At the same time, the same law reduces to zero the voltage on

output (terminal 4) of the device (Fig. 3, the interval tz - ti). At the moment when the output voltage is zero at the output of the comparator 6 becomes high, the RS flip-flop 8 is set to the zero state at the output, which blocks the passage of pulses to the input of the counter 10. Thus, at time t2, zero voltage is set at the output terminal 4 and the output of a digital-to-analog converter

11 is a voltage proportional to Rx °. If at time t2 the resistance of the resistive sensor 3 begins to change, a voltage appears at the output 4 of the device (Fig. 3).

 -Arx.

where A Rx is the change in the voltage value of the resistive sensor 3.

Thus, the proposed device allows it to be used for mass measurement of resistor parameters such as temperature coefficient of resistance and temporal stability of resistance at elevated operating temperatures. In addition, the need for an additional power source is eliminated, and the influence of resistance

due to the high output impedance of the current-stabilizing element and the high input impedance of the operational amplifier.

Claims (1)

Invention Formula Device for measuring the increment of the resistance, containing the source the reference voltage, the first output of which is connected to the common bus, the operational amplifier, the output of which is connected to its inverting input and the first terminal for connecting a resistive sensor, the second terminal for connecting a resistive sensor connected to the output of the device and the output of the current stabilizing element, the input which is connected to the second output of the source of the reference voltage 5, characterized in that, in order to increase speed, a comparator and a voltage storage unit connected between the output and non-inverting input of the comparator the amplifier, the first input of the comparator of the connection, and the second input of the comparator is connected thereto to the output of the current-stabilizing element with a common bus. t 7 WV Fie.2