SU987377A1 - Two-channel strain gauge device - Google Patents

Description

The invention relates to a measuring technique, namely, devices for measuring deformation and forces.

A strain gauge device is known that contains two cable bridges, each of which is connected to the input of a switch connected in series with an amplifier, a phase-sensitive demodulator, a low-frequency filter, an analog-to-digital converter and a flj regenerator

The disadvantage of a strain gauge device is low sensitivity due to magnitudes; errors introduced by the switch.

The closest to the technical essence of the invention is a two-channel strain gauge device containing two measurement channels, of which consists of a series-connected load bridge and quadrature component filter, amplifier) to whose inputs the outputs of the quadrature filter are connected, the outputs of the amplifier are connected to the two phase-sensitive demodules tori, each of which is consistently connected to a low-frequency filter

and the recorder, a carrier voltage generator, the outputs of which are connected to the inputs of the load bridge and the quadrature filter component of the first channel and the input of one of the phase-sensitive demodulators, the phase shifter whose input is connected to one of the inputs of the carrier voltage generator, and the outputs 10 with inputs a strainer, an input of the quadrature filter component of the second channel and the input of another Phase-Sensitive Demodulator C2.

A disadvantage of this device is the low measurement accuracy due to the non-identity of the amplitude-frequency and phase-frequency parameters of the nodes and elements included in the two-channel strain gauge device.

20

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

This goal is achieved by the fact that a two-channel strain gauge device containing two channels of 25 nyureni, each of which consists of a series-connected tevoekyust and quadrature component filter, an amplifier, to the inputs of which are connected the outputs of quadrature component filters

but the connected phase-sensitive demodulator, low-frequency filter and recorder, the output of the plug-in amplifier to the phase-sensitive demodulator input, the carrier voltage generator, the output of which is connected to the input of the first bridge and the quadrature component of the first channel, the phase shifter whose input is connected to one of the generator outputs of the carrier voltage, and the output with the inputs of the strain gauge and quadrature filter of the second channel, is equipped with an analog-digital converter, the input of which is connected to low pass filter output and switch, first. the input of which is connected to the output of the carrier voltage generator; the second input is connected to the output of the phase shifter, the control input is connected to the control output of the recorder, and the output is to the reference input of the phase-sensitive demodulator.

The drawing shows a block diagram of the proposed device.

The two-channel strain gauge device contains in the first channel serially connected strain gauge 1, filter 2 of the field component, amplifier 3, phase-sensitive demodulator 4 with a filter of 5 low frequency, analog-digital converter B. (ADC) and recorder 7. The second channel of measurements contains Consistently connected strain gauge 8, low-frequency filter and amplifier 3. The output of the recorder 7 is connected to the control input of the switch 10, the first input of which is connected to the output of the generator 11 of the carrier voltage, second input connected to the output fazovray1atel 12 and the output of the switch 10 is connected to a reference input of a phase-sensitive demodulator 4. The output 11 is coupled to the carrier frequency tenzomostom 1, a filter 2 of the quadrature component of the phase shifter and the input of phase shifter 12. The output:. 12 is connected to a tensome bridge 8 and a filter of a 9 square leading component.

The device works as follows.

The supply voltage of the strain gauge 1 and the reference voltage of the filter 2 quadrature component is shifted in phase by 90 relative to the voltage supply of the strain gauge B and the reference voltage of the filter 9 quadrature component. For this, the voltage of the generator 11 of the carrier frequency, which is the power source of the strain gauges 1 and 8 and the source of the reference voltage of the filters 2 and 9 of the quadrature component and the phase-sensitive demodulator 4, is shifted in phase

a phase shifter 12, and then supplied to a strain bridge 8 and a filter 9 of a square component. As a result, modulated oscillations are formed at the inputs of the fi rms 2 and 9 of the quadrature component, in which, for example, the yields of the carrier frequencies are shifted by 90.

From the outputs of the filters 2 and 9 of the quadrature component, signals are fed to the input of amplifier 3 and after 0 amplification they go to the signal

the input of the phase-sensitive unit 4, the reference input of which is supplied by the reference voltage from the output of the switch 10. Thus, the reference input of the phase-sensitive demodud type 4 is alternately supplied to alternating voltage, respectively, with voltage of the strain gauge 1 and eight.

0 in the interval when the phase-sensitive demodulator 4 from the output of the switch 10 is supplied with a voltage in phase with the supply voltage of the tension bridge 1, at the output of the demodulator 4

25, a signal is generated that is proportional to the magnitude of the output voltage of the strain bridge 1. In the interval when demodulator 4 is output from the switch 10; an in-phase voltage is supplied with the voltage of the power supply of the tension bridge 8, the output of the demodulator 4 produces a signal proportional to the output voltage of the tension bridge 8. The duration of these intervals

5 is determined by the duration of the low-frequency signal periods at the outputs of the tension bridge 1 and 8. From the output of the phase-sensitive demodulator 4, the signal is fed to the 5th frequency filter input, and from its output to the ADC input b.

The DCA 6 converts the analog signal to a digital code proportional to the amplitude value of the input signal, which is fed to the input of the recorder 7. The recorder 7 displays the measurement result and controls the operation of the switch 10, allowing it to switch after the previous measurement is completed.

Thus, the invention provides an increase in the measurement accuracy by reducing the instrumental errors associated with the non-identity of the amplitude-frequency and phase-frequency characteristics of the nodes, and the elements entering the device.

Claims (2)

1. Works tX conference on automatic control and methods of electrical measurements. Novosibirsk Science, 1970, 169. 2. USSR author's certificate  2,68680, class G 01 B 7/16, 1967 (prototype).