How to solve the drift of electromagnetic flowmeter
Release time:
2021-08-06
How to solve the drift of electromagnetic flowmeter
In the process of using electromagnetic flowmeter, sometimes the electromagnetic flowmeter will drift. In this case, how should we solve it? Next, Kaifeng open flow instrument Co., Ltd., the manufacturer of electromagnetic flowmeter, will introduce the solutions, which are mainly divided into three types:
1. Elimination of differential interference and power frequency interference
Differential interference and power frequency interference often exist in the signal at the same time. It is difficult to filter out the power frequency interference completely by low-pass filtering in the signal processing circuit. Synchronous sampling and power frequency compensation technology need to be adopted to suppress power frequency interference mixed with power frequency interference and power frequency fluctuation in flow signal potential, and effectively eliminate differential interference. Synchronous sampling technology, the sampling start time lags behind the excitation signal by 1 / 4 cycle, and the pulse width is even times of the power frequency cycle, so as to eliminate the differential interference and make the average value of power frequency interference in the potential of flow signal equal to zero, so as to eliminate the influence of power frequency interference; The frequency fluctuation compensation of power frequency power supply is to ensure that the excitation power supply and sampling pulse can be adjusted synchronously in the dynamic fluctuation of frequency, truly realize the synchronous sampling technology and synchronous excitation technology and synchronous A / D conversion, and reduce the influence of differential interference and power frequency interference.
2. Zero drift elimination
The so-called zero drift is that when the input signal of the sensor is zero, the output of the amplifier is not zero. The signal of zero drift will be transmitted between amplified circuits at all levels. After multistage amplification, it will become a large signal at the output end. Because the useful signal output by the sensor is weak, the zero drift may drown the useful signal and make the circuit unable to work normally. Therefore, in order to suppress the zero drift, the differential circuit input of three operational amplifiers is used to collect the weak signal with large internal resistance, so as to suppress the introduction of common mode signal. After the primary amplification circuit, the DC isolation capacitor is used to filter the baseline zero drift and prevent the DC signal from exceeding the input range of a / D conversion.
3. Other measures to remove interference
For the orthogonal interference caused by the "transformer effect" of the electromagnetic flowmeter sensor, the "transmitter zeroing method" is used to eliminate it. In terms of software design, digital filtering technology, power failure protection technology and software instruction redundancy measures can effectively improve the reliability of digital input microprocessor.
The above information is provided by Kaifeng open flow instrument Co., Ltd., a manufacturer of electromagnetic flowmeter. For more information about electromagnetic flowmeter, please continue to pay attention to our website!
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