CN104266692A - Dual excitation electromagnetic flowmeter - Google Patents

Abstract

The invention discloses a double-excitation electromagnetic flowmeter, which comprises: the excitation device of the invention provides excitation current for the excitation coil in two different excitation periods, and selectively converts the two excitation periods, so that initial flow signals of two excitation frequencies can be obtained, measurement errors caused by induction noise can be effectively eliminated, zero point adjustment for stopping fluid flow is not required, the measurement precision is improved, and the reliability is high.

Description

Dual excitation electromagnetic flowmeter

technical field

The invention relates to a double excitation electromagnetic flowmeter.

Background technique

The weight function of the electromagnetic flowmeter is a fictitious physical quantity. Its physical meaning is: when the electromagnetic flowmeter is working, it measures the contribution of the induced electromotive force generated by each point in the pipe space to the output voltage between the electrodes. Scientists have made a clear definition of the numerical value of the weight function of a certain point in the pipe space measured by the electromagnetic flowmeter, that is, when the unit current flows through two electrodes to form a current loop, the current density of the point. Therefore, there are also many literatures that call the weight function virtual current, and the measurement system of the electromagnetic flowmeter is used to calculate the flow through this current. However, the current electromagnetic flowmeters all use a fixed period of excitation cycle, so each time The flow data obtained are all based on the excitation cycle, and the reliability of the measurement is not high.

Contents of the invention

In order to overcome the deficiencies of the prior art, the invention provides a double excitation electromagnetic flowmeter.

The technical solution adopted by the present invention to solve its technical problems is:

Dual excitation electromagnetic flowmeter, including: 

Exciting coils arranged on the upper and lower sides of the measuring tube, the exciting coils provide a magnetic field to the inside of the measuring tube;

an excitation device, the excitation device is connected with the excitation coil, and provides excitation current to the excitation coil with two different excitation cycles;

An electrode, which is arranged on the left and right sides of the measuring pipe, is used to detect the current generated by cutting the magnetic field line by the flow in the measuring pipe;

a signal processing circuit, the signal processing circuit is connected to the electrodes and is used to process the current signals detected by the electrodes;

an A/D converter connected to a signal processing circuit for converting an analog signal into a digital signal;

a microprocessor connected to an A/D converter for extrapolating flow from said electromotive force generated during said excitation cycle when an electromotive force is generated between said electrodes in each of said excitation cycles signal, the microprocessor is also connected with the excitation device to switch between different excitation cycles.

The microprocessor performs an extrapolation operation based on a linear function of the excitation period.

The signal processing circuit includes an amplifier circuit and a filter circuit, and the signal is output after passing through the amplifier circuit and the filter circuit in sequence.

It also includes a display connected to the microprocessor.

The microprocessor is preferably the MSP430 single-chip microcomputer of Hong Kong TI company or the 80C552 single-chip microcomputer of Netherlands PHILIPS company.

The beneficial effect of the present invention is that: the excitation device of the present invention supplies the excitation current to the excitation coil with two different excitation periods, and selectively switches the two excitation periods, so that the initial flow signals of two excitation frequencies can be obtained, The measurement error caused by the induction noise can be effectively eliminated, the measurement accuracy is improved, and the reliability is high.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a schematic diagram of the structure of the present invention.

Detailed ways

Referring to Fig. 1, Fig. 1 is a structural principle diagram of a specific embodiment of the present invention, as shown in the figure, 1 double excitation electromagnetic flowmeter, comprising:

The excitation coil 2 arranged on the upper and lower sides of the measuring tube, the exciting coil 2 provides a magnetic field to the inside of the measuring tube;

an excitation device, the excitation device is connected with the excitation coil, and provides excitation current to the excitation coil with two different excitation cycles;

Electrode 1, the electrode 1 is arranged on the left and right sides of the measuring pipe fitting, and is used to detect the current generated by cutting the magnetic force line of the flow in the measuring pipe fitting;

A signal processing circuit, the signal processing circuit is connected to the electrode 1, and is used to process the current signal detected by the electrode 1;

an A/D converter connected to a signal processing circuit for converting an analog signal into a digital signal;

a microprocessor connected to an A/D converter for extrapolating flow from said electromotive force generated during said excitation cycle when an electromotive force is generated between said electrodes in each of said excitation cycles signal, the microprocessor is also connected with the excitation device to switch between different excitation cycles.

The excitation device of the present invention provides the excitation current to the excitation coil 2 with two different excitation periods, and selectively switches the two excitation periods, so that the initial flow signals of two excitation frequencies can be obtained, which can effectively eliminate the The measurement error caused by noise is eliminated, and the measurement accuracy is improved, and the reliability is high.

Further, the signal processing circuit includes an amplifier circuit and a filter circuit, and the signal is output after passing through the amplifier circuit and the filter circuit in sequence, that is, the filter circuit filters the output of the signal amplifier circuit to reduce the influence of interference noise and obtain the fundamental wave of the flow velocity signal, And make the power of various interference noises decrease as the bandwidth decreases, improve the signal-to-noise ratio, and improve the measurement accuracy of the electromagnetic flowmeter.

As preferably, the microprocessor is preferably MSP430 single-chip microcomputer of Hong Kong TI company or 80C552 single-chip microcomputer of Netherlands PHILIPS company, and the said microprocessor is also connected with a display to display the flow measurement result.

Preferably, the microprocessor performs extrapolation according to a linear function of the excitation period.

The preferred implementation of the present invention has been described in detail above. Of course, the present invention can also adopt different forms from the above-mentioned embodiments. Those skilled in the art can make equivalent transformations or corresponding equivalents without violating the spirit of the present invention. Any changes should fall within the protection scope of the present invention.

Claims (5)

1. Double excitation electromagnetic flowmeter, characterized in that: including: Exciting coils (2) arranged on the upper and lower sides of the measuring tube, the exciting coils (2) provide a magnetic field to the inside of the measuring tube; an excitation device, the excitation device is connected with the excitation coil, and provides excitation current to the excitation coil with two different excitation cycles; An electrode (1), the electrode (1) is arranged on the left and right sides of the measuring pipe fitting, and is used to detect the current generated by cutting the magnetic field line by the flow in the measuring pipe fitting; A signal processing circuit, the signal processing circuit is connected to the electrode (1), and is used to process the current signal detected by the electrode (1); an A/D converter connected to a signal processing circuit for converting an analog signal into a digital signal; a microprocessor connected to an A/D converter for extrapolating flow from said electromotive force generated during said excitation cycle when an electromotive force is generated between said electrodes in each of said excitation cycles signal, the microprocessor is also connected with the excitation device to switch between different excitation cycles. 2. The dual-excitation electromagnetic flowmeter according to claim 1, characterized in that: the microprocessor performs extrapolation according to the linear function of the excitation period. 3. The dual-excitation electromagnetic flowmeter according to claim 1, wherein the signal processing circuit includes an amplifier circuit and a filter circuit, and the signal is output after passing through the amplifier circuit and the filter circuit in sequence. 4. The dual-excitation electromagnetic flowmeter according to claim 1, further comprising a display connected to the microprocessor. 5. The double excitation electromagnetic flowmeter according to claim 1, characterized in that: said microprocessor is preferably MSP430 single-chip microcomputer of Hong Kong TI company or 80C552 single-chip microcomputer of Netherlands PHILIPS company.