SU885807A1 - Electromagnetic flowmeter - Google Patents

Description

(54) ELECTROMAGNETIC FLOW METER

one

The invention relates to the measurement of the consumption of electrically conductive liquids by an electromagnetic method.

Electromagnetic flowmeters are known that contain a fluid flow sensor / compensation unit of a useful component of a sensor signal, an error amplifier, a synchronous detector, a voltage source and a galvanometer operating in the transformer converter mode 1.

However, the performance of these flow meters is low, which is explained by the need to use an inertial filter at the output of the synchronous detector to eliminate pulsations produced by the uncompensated quadrature component of the sensor output signal that reaches half the amplitude of the useful component. In addition, flowmeters have limited accuracy, which is explained by the low gain factor — the error amplifier. This factor cannot be chosen large because there is always an uncompensated quadrature signal at the input of the amplifier, and there is a danger that the amplifier will saturate it.

signal. Well-known flow meters also have a low level of confidence due to the presence in their composition of a moving frame of a galvanometer that is sensitive to vibrations and other mechanical effects.

The purpose of the invention is to improve the measurement accuracy and speed of the flow meter.

ten

This goal is achieved by the fact that an electromagnetic flowmeter containing a flow sensor, a compensation unit of the useful component of the sensor signal, the error amplifier

15 and a reference voltage source, the first input of the compensation unit of the useful component of the sensor signal is connected to the output of the flow sensor, additionally equipped with two phase pulse formers and a phase pulse comparison circuit, the output of the flow sensor connected to the first inputs of both phase pulse formers, to the second

25 to the input of the first shaper, the source of the reference voltage is connected to the second input of the second shaper of the phase pulses — the output of the compensation unit of the useful signal

JO of the sensor, the outputs of both formers of phase pulses are connected to the inputs of the phase pulse comparison circuit, the output of which is connected via the error amplifier to the second input of the compensation block of the useful 17 (its sensor signal.

Fig, a functional diagram of the electromagnetic flow meter; in fig. 2 - timing flow meter operation.

The device comprises a flow sensor 1, a first 2 and a second 3 phase pulse formers, a compensation component block 4 of the useful signal of the sensor signal, a phase pulse comparison circuit 5, and an error amplifier b.

The output of the flow sensor 1 is connected to the first inputs of phase formers 2 and 3, and to the first input of compensation unit 4 of the useful component of the sensor signal, the output of which is connected to the second input of the phase imaging unit 3 phase pulses. The second input of the phase generator 2 phase pulses is connected to the reference voltage source Up-,, and the outputs of the phase pulse drivers 2 and 3 are connected to the inputs of the phase pulse comparison circuit 5, the output of which is connected to the input of the error amplifier 6. The output of amplifier 6 is connected to the second input of the compensation unit 4 of the useful component of the sensor signal. Misalignment amplifier b is performed by filtering.

The flow meter works as follows.

The output signal of sensor 1, which contains a pixel signal and quadrature interference (Fig.2a), is fed to the first inputs of the formers 2 and 3 phase pulses, which at the time of crossing the zero signal of the sensor simultaneously form the leading edges of two phase -1pulses {fig.2b and 2d ) The reference voltage signal is fed to the second input of the former 2 phase impulses, at the time of crossing the reference voltage, the trailing edge of the first phase pulse is formed (Fig. 2c). The reference signal (Fig. 2b) is shifted by 90 relative to the useful component of the signal from sensor 1. The duration of the first phase pulse is tj, where is the phase shift between the output signal of sensor 1 and the reference signal;

a (jj 23Г, where f is the frequency of the supply voltage.

The signal of sensor 1 is compared in block 4 of the compensation of the useful component of the sensor signal, which is a voltage comparator with the output voltage of the error amplifier. At the instant of equality of the instantaneous value of the input voltage and voltage from the output of the error amplifier B at the output of block 4, a voltage drop occurs, which is fed to the second input of the driver 3 phase pulses and. forms the trailing edge of the second phase pulse. Depending on the level of the direct voltage at the output of the error amplifier 6, the trailing edge of this phase pulse moves. The duration of the second phase pulse is determined from the ratio 6bix 8i (... Sinujt

Sheni

Ip

and,

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qrosin UBX

 Uj

Phase pulses (Figs. 2c, d) from the outputs of blocks 2 and 3 are fed to the inputs of the phase pulse comparison circuit 5, which separates the difference phase pulse (Fig. 2d), the latter is amplified and smoothed by the error amplifier b and creates an output voltage of steady state Both phase pulses 5 are equal in duration with an accuracy determined by the static error, which, with a large gain, can be reduced to zero, i.e.

qrcsin

ABOUT.

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Thus, the output of the flow meter is determined only by the useful component of the flow signal,

The use of the proposed flow meter improves the accuracy of flow measurement.

Claims (1)

1. Katys G.P. Systems of automatic control of speed and expense fields. M., Science, 1965, p. 365-366 (prototype).