CN203811213U - Signal adjustment circuit of electromagnetic flowmeter - Google Patents

Abstract

The utility model provides a signal regulating circuit for an electromagnetic flowmeter. The development and application history of the electromagnetic flowmeter is the development history of an anti-interference technology of the electromagnetic flowmeter. Particularly for the processing of micro flow rate measuring signals, the noise interference is greater, and the flow rate signals are very weak, so the modulation circuit cannot perfectly eliminate the influence of higher harmonics and additive noise on the signals. The signal regulating circuit consists of an electromagnetic sensor (1), wherein the electromagnetic sensor is connected with a high-performance operation amplifier (2) and a phase-locked loop (6) through electrode output signals, the high-performance operation amplifier is connected with a multiplicative D/A (digital to analog converter) (3), the phase-locked loop is connected with a frequency divider (7), the frequency divider is connected with an ROM (read only memory) (8), the ROM is connected with the multiplicative D/A, and the multiplicative D/A is connected with a low-pass filter. The utility model relates to the signal regulating circuit for the electromagnetic flowmeter based on a digital and analog mixed correlation measurement method.

Description

Signal adjustment circuit of electromagnetic flowmeter

Technical field:

The utility model relates to a signal conditioning circuit of an electromagnetic flowmeter based on a digital-analog mixed correlation measurement method, that is, to a signal conditioning technology of an electromagnetic flowmeter applied to weak flow detection.

Background technique:

The history of the development and application of electromagnetic flowmeters is the development history of its anti-interference technology, especially in the processing of micro-flow measurement signals. Due to the large noise interference and the very weak flow signal, in the known electromagnetic flowmeters, The conditioning of the flow signal generally uses a peak sample-and-hold circuit. This conditioning circuit cannot well eliminate the influence of high-order harmonics and additive noise on the signal, resulting in low signal-to-noise ratio, poor resolution, and difficulty in obtaining the lower limit of flow measurement. Extended question.

Utility model content:

The purpose of the utility model is to provide a signal adjustment circuit of an electromagnetic flowmeter.

The purpose of this utility model is achieved in that:

A signal adjustment circuit of an electromagnetic flowmeter, which consists of: an electromagnetic sensor, the electromagnetic sensor connects the output signal to a high-performance operational amplifier and a phase-locked loop through electrodes, and the high-performance operational amplifier and a multiplication D/ A connection, the phase-locked loop is connected to the frequency divider, the frequency divider is connected to the ROM memory, the ROM memory is connected to the multiplication type D/A, and the multiplication type D/A connected to a low-pass filter.

The signal adjustment circuit of the electromagnetic flowmeter, the voltage connector between the electrodes of the electromagnetic sensor is connected to the reference voltage input terminal of the multiplication type D/A through the operational amplifier, and the electromagnetic sensor The voltage terminals between the electrodes are connected to the input terminals of the phase-locked loop.

In the signal adjustment circuit of the electromagnetic flowmeter, the output end of the phase-locked loop is connected to the clock end of the frequency divider, the output end of the frequency divider is connected to the address input end of the ROM, and the ROM The data port is connected to the data input port of the D/A.

In the signal adjustment circuit of the electromagnetic flowmeter, the output end of the D/A converter is connected with a low-pass filter.

Beneficial effect:

1. This utility model adopts an algorithm based on the digital-analog mixed correlation measurement method to perform optimal filtering on the signal. The conditioned signal is added to the reference voltage terminal of the multiplication D/A converter through the signal amplifier, and is synchronized with the same frequency stored in the ROM. The digital signal is multiplied in the D/A converter, and the low-pass filter is used to achieve the integral and average operation to obtain the output signal with the optimal signal-to-noise ratio. This kind of circuit has the function of adjusting the ground with the optimal signal-to-noise ratio, can effectively suppress noise, improve resolution, and expand the lower limit of measurement of the electromagnetic flowmeter.

The utility model adopts a digital-analog hybrid optimal matching filter method, which can realize the output of the maximum signal-to-noise ratio of the measured voltage signal, realize accurate measurement of the weak flow signal, and improve the performance index of the electromagnetic flowmeter.

The utility model adopts a signal synchronization circuit composed of a phase-locked loop circuit and a counter to realize the same-frequency synchronization of digital and analog signals.

The utility model simplifies the realization of the circuit by adopting the low-pass filter instead of the integral to calculate the average.

The utility model can separate the conditioning output signal with the best signal-to-noise ratio in the noise environment, improve the resolution, and expand the lower limit of flow measurement.

Description of drawings:

Accompanying drawing 1 is the structural diagram of signal conditioning circuit of digital-analog hybrid optimal filtering method of the present utility model.

Accompanying drawing 2 is amplifier circuit.

Accompanying drawing 3 is the signal synchronous circuit that phase-locked loop and frequency divider form.

Accompanying drawing 4 is a digital signal generation circuit.

Accompanying drawing 5 is an analog digital multiplier circuit.

Accompanying drawing 6 is a low-pass filter circuit.

Detailed ways:

Example 1:

A signal adjustment circuit for an electromagnetic flowmeter, the electromagnetic sensor electrode output signal u(t) 1, the electromagnetic sensor electrode output signal u(t) is connected to a high-performance operational amplifier 2 and a phase-locked loop 6, and the high-performance The operational amplifier is connected to the multiplying D/A3, the phase-locked loop is connected to the frequency divider 7, the frequency divider is connected to the ROM memory 8, and the ROM memory is connected to the multiplying D/A , the multiplying D/A and low-pass filter are connected 4. The utility model relates to an electromagnetic flowmeter signal conditioning circuit based on a digital-analog hybrid correlation measurement method.

Example 2:

According to the signal adjustment circuit of the electromagnetic flowmeter described in Embodiment 1, the voltage u(t) between the electrodes of the electromagnetic sensor is added to the reference voltage input terminal of the multiplication D/A through the operational amplifier, At the same time, the voltage u(t) between the electrodes of the electromagnetic sensor is added to the input terminal of the phase-locked loop, and the output signal u(t) of the electrodes of the electromagnetic sensor is realized as a digital-to-analog signal through the phase-locked loop Synchronize with the same frequency.

Example 3:

According to the signal adjustment circuit of the electromagnetic flowmeter described in embodiment 1 or 2, the output terminal of the phase-locked loop is added to the clock terminal of the frequency divider as a clock control signal, and the output of the frequency divider As the ROM address input that stores the digital signal u'(t) of the same frequency and type as u(t), the data port of the ROM is connected to the data input port of the D/A, thus realizing the input signal u(t) and u' (t) Same-frequency synchronous multiplication.

Example 4:

According to the signal adjustment circuit of the electromagnetic flowmeter described in embodiment 1 or 2 or 3, the output signal of the D/A converter is passed through a low-pass filter, and the second-order filter with a low corner frequency is equivalent to an integrator to realize The DC output signal u0 5 is obtained by integrating and averaging, and the digital-analog hybrid optimal filter conditioning of the signal between the electrodes of the electromagnetic sensor is completed.

Example 5:

The utility model adopts low-frequency rectangular wave current excitation, first stores the digital quantity corresponding to the square wave signal of the low-frequency excitation current in one cycle in ROM, and then outputs the sensor electrode square wave output signal u(t) proportional to the flow rate through The high-performance operational amplifier is amplified to 0-5v and added to the reference voltage terminal of the multiplying D/A converter; at the same time, u(t) is then added to the input terminal of the phase-locked loop, and its output is used as the clock input of the frequency multiplication circuit , the output of the frequency multiplication circuit is used as the address signal of the ROM and the data output port of the ROM is connected to the digital input port of the D/A converter to realize digital-analog mixed multiplication, and finally the analog output of the D/A converter is passed through the cut-off frequency The low-pass filter of 0.5Hz uses the low-pass filter to complete the integration and averaging operation, so as to obtain the maximum signal-to-noise ratio direct current output proportional to the flow rate.

Claims (3)

1. the signal adjustment circuit of an electromagnetic flowmeter, its composition comprises: electromagnetic sensor, it is characterized in that: described electromagnetic sensor is connected to high performance operational amplifier and phaselocked loop by electrode handle output signal, described high performance operational amplifier is connected with multiplication type D/A, described phaselocked loop is connected with frequency divider, described frequency divider is connected with ROM storer, and described ROM storer is connected with described multiplication type D/A, and described multiplication type D/A is connected with low-pass filter.

2. the signal adjustment circuit of electromagnetic flowmeter according to claim 1, it is characterized in that: the interelectrode voltage jointer of described electromagnetic sensor is connected to the reference voltage input terminal of described multiplication type D/A through described operational amplifier, interelectrode described electromagnetic sensor voltage terminal is connected to the input end of described phaselocked loop simultaneously.

3. the signal adjustment circuit of electromagnetic flowmeter according to claim 1 and 2, it is characterized in that: the output terminal of described phaselocked loop is connected to the clock end of described frequency divider, described frequency divider output terminal is connected to the address input end of ROM, and the FPDP of described ROM is received the data-in port of described multiplication type D/A.