SU550524A1 - Device for measuring physical quantities - Google Patents

Description

one

The invention relates to the field of instrumentation engineering, in particular, to the construction of devices for measuring physical quantities.

A device for measuring physical quantities is known, comprising a sensor comprising a primary and two secondary windings, a constant voltage source, a stabilized Zener diode, a blocking separator, and a measurement channel 1.

This device is sufficiently widely used to measure, for example, movements. However, it has a number of drawbacks: low accuracy due to the presence of a high level of external harmonic components of the output voltage of the blocking generator, as well as the impossibility of powering the sensor of the device from the AC network.

It is also known a device for measuring physical quantities, which contains a droplet of measurement and a sensor connected to it, powered by alternating current 2. This device is the closest in technical essence to the invention, however, it does not solve the problem of compensating the sensor error from the instability of the parameters supplying it network.

In order to improve the measurement accuracy, the proposed device is supplied with a source of alternating and reference voltages, null-or2.

An analog switch and a rectifier, the measurement channel with its output is connected to one of the inputs of the analog switch, to another input of which sources of alternating and reference voltages are connected via a null organ, and the output of the analog switch is connected to the rectifier.

The drawing shows a block diagram of the device.

The device contains a sensor 1 powered by alternating current, a channel 2 of measurement, a source 3 of an alternating voltage, a source 4 of a supporting voltage, a null organ 5, an analog switch 6, a rectifier 7.

The device works as follows.

When a measured value is applied to a sensor, an alternating current signal is generated at its output, the amplitude of which is proportional to the measured physical quantity and

the parameters (voltage, frequency) of the supply network. This signal is transformed in the measurement channel into proportional DC voltage and is fed to one of the inputs of the analog switch, which generates rectangular DC pulses at the output with a duty cycle depending on the value of the deviation of the power supply parameters from the nominal, converted into rectifiers DC voltage proportional to the measured physical quantity. At the same time, the voltage proportional to the current parameters of the supply network from the source 3 is applied to one of the inputs of the null organ, and the other input of the zero organ from the source 4 of the reference voltage receives a direct current voltage proportional to the nominal parameters of the power supply network. The nullorgan compares these voltages and outputs a signal that is fed to another input of the analog key, opening or closing it. The frequency of opening the key 6 is constant, and the time of opening it is determined by the value of the parameters of the power supply network.

With the nominal network parameters, the duty cycle of the pulses generated by the key 6 is constant and equal to the nominal value. When the network parameter changes (for example, an increase in the frequency or frequency), the voltage of sensor 1 increases and the voltage of source 3 increases, while the opening time of the key decreases inversely with the increase in voltage of the alternating voltage source. The magnitude of the voltage produced by the signal at the time of opening the key is kept constant, i.e. it does not depend on changes in the parameters of the power supply network.

The same constant value is the product of the voltage of the signal at the time of opening the key when the voltage or frequency of the power supply decreases. The open-close frequency of the key is chosen higher than the frequency of the measured signal by more than two orders of magnitude, which ensures accurate reproduction of the character of the signal of the measured value.

The effectiveness of this device is determined by its ability to eliminate the effect of changing voltage parameters on the accuracy of the measuring device when powered by the sensor both from the network and from another unstabilized source of alternating voltage. The accuracy that has been achieved in this device without increasing its cost is one or two classes higher than similar devices.

Claims (2)

1. The copyright certificate number 366341, M. Kl.2 G 01 B 7/02, 1971 (equivalent). 2.B. I. Blazhkevich et al., “Digital devices of combined balancing, pp. 18-19, 1973 (prototype).