SU901827A1 - Electromagnetic flowmeter with frequency output - Google Patents

Description

one

The invention relates to a measurement technique and is intended to measure the flow rate of a liquid by an electromagnetic method with analog-to-digital conversion of the flow rate of a liquid.

A electromagnetic flowmeter with a compensation circuit for converting a date-to-frequency signal is known, which contains a sensor, an excitation coil, a magnetic field, an amplifier, and two identical conversion channels, each of which has phase detectors, voltage converters — frequency and frequency — on, 5 bridging with appropriate filters 1.

However, the design of such a flow meter is complicated. The magnetic field is excited in it by an industrial frequency, therefore, a large full power is required for the excitation. At an industrial frequency, there is a rather significant transformer interference, for suppressing which an additional channel is used.

A electromagnetic flow meter with a frequency output is known, whose excitation frequency is equal to the output frequency, which contains a sensor, a sensor signal amplifier, a series-connected control circuit, a triangular current generator, and a magnetic field excitation coil of the sensor magnetic field, and first and second comparison circuits, whose outputs are connected to the input of the circuit management With a low excitation frequency, the total power and transformer disturbance t2 are significantly reduced.

A disadvantage of the known flow meter is the low measurement speed. Due to fluctuations of the instantaneous flow rate and unstable electrode potentials, each period of the flow meter output signal is determined with a certain error. However, since the errors are purely random and uncorrelated among themselves, the total relative error in determining the frequency according to the formula f s, where Tg is the reference time interval, N is the number of pulses that occurred at the output of the flow meter during this interval, will be VN times less. Since the most advantageous both from an energy and metrological point of view is the range of excitation frequencies below the power frequency, a sufficiently large exemplary period of time Td is necessary to obtain information about the flow rate with a given accuracy. The purpose of the invention is to increase the flow rate of the flow measurement at a given accuracy. This goal is achieved by the fact that an electromagnetic flow meter with a frequency output containing a sensor, a sensor signal amplifier, a serially connected control circuit, a triangular-shaped current generator, the excitation coil of the Max-field of the sensor, and the first and second comparison circuits whose outputs are connected An input is added to the input of the circuit, the comparison circuit and a pulse accumulator, the inputs of the first and input comparison circuits are connected to the output of the sensor signal amplifier, the input of the second comparison circuit is connected generator current triangular shape, and O all rows comparing circuits are connected to an adder pulses. The flow chart is shown in the drawing. The flow meter consists of a sensor 1 to the electrodes of which the amplifier 2 of the sensor signal is connected. The magnetic field in the sensor 1 is created by a magnetic field excitation coil 3 connected to the output of the current generator k, of a triangular shape, the input of which is connected to the control circuit 5. The inputs of the latter are connected to the outputs of the first comparison circuit 6 and the second comparison circuit 7, the input of which is connected to the generator 3 of the triangular current. The output of the flow meter is an adder of 8 pulses, to the input of which the outputs of all circuits 6.7, 9-2, .. are connected - a 9-n comparison. The inputs of the circuits 4 6, 9-1, 9-2, ..., 9-p, the comparison is connected to the output of the amplifier 2 sigHia sensor. The device works as follows. At the moment of switching on, the current at the output of the triangular current generator starts to grow linearly. At the same time, the induction of the magnetic field in sensor 1 also increases linearly, the useful signal on its electrodes and the signal at the output of amplifier 2 of the sensor signal. At the moment when the signal at the amplifier output reaches the value of Un, where EO is the threshold of operation of the first comparison circuit 6, the latter triggers, affecting the control circuit 5, which in turn switches the direction of current change at the generator output t of the triangular form. The current begins to decrease linearly until its value becomes zero. At this moment, the second comparison circuit 7 operates and acts on the control circuit 5, which again switches the generator k. The frequency of a triangular current is proportional to the fluid flow where Q is the flow, B is the speed of a magnetic field, proportional to the rate of a triangular current, C - constant. The triggering thresholds of the circuits, 9 -2 ..., 9P comparisons are chosen equal to about 7 °, 2. .. n-number of comparison circuit 9. In each period, all comparison circuits 9 are triggered two times: as the signal at the output of amplifier 2 increases from O to EO and when this signal decreases from E to 0. If the fluid flow during one period T is constant, then the time interval between operations the corresponding comparison circuits will be Y, where n is the number of comparison circuits 9 in the flowmeter circuit. At the output of the adder 8 pulses, the pulses appearing at the outputs of all comparison circuits will appear, so the repetition frequency of the pulses at the output of the latter will be 2 and | 1c, where fu is the hour

Claims (1)

Claim An electromagnetic flowmeter with a frequency output, comprising a sensor, an amplifier of the sensor signal, a control circuit connected in series, a triangular mince current generator, a magnetic field excitation coil, and a first and second circuit. Comparisons, the outputs of which 5 are connected to the control circuit a) that in order to increase the quick action, η comparison circuits and an adder of pulses are additionally introduced into it, and the inputs of the first and n input comparison circuits are connected to the output of the sensor signal amplifier, the input is second The comparison circuit is connected to a current generator 15 of a triangular Forsch, and the outputs of the comparison circuits are connected to the pulse adder.