The quantitative control sewage flow meter consists of two parts: the sensor and the converter. It works according to Farad's law of electromagnetic induction. The quantitative control sewage flow meter is widely used in chemical fiber, food, papermaking, sugar making, mining, water supply and drainage, environmental protection, water conservancy and hydraulic engineering, steel, petroleum, pharmaceutical and other industrial fields to measure the volume flow of various acid and alkali, salt solution, mud, ore pulp, pulp, coal water slurry, corn pulp, fiber pulp, grain pulp, lime milk, sewage, cooling raw water, water supply and drainage, brine, hydrogen peroxide, beer, wort, various beverages, black liquor, green liquor and other conductive liquid media.

The main reasons for the zero drift of the quantitative control sewage flow meter are as follows:

(1) A certain section of the flow measurement tube upstream and downstream is not filled with liquid, but the axial flow velocity flowing through the electrode has a certain amplitude of swing. Although the amplitude of this swing is very small, it can still be observed because the accuracy of the quantitative control sewage flow meter has reached a very high level.

(2) A layer of insulating material is adhered to the surface of the electrode.

(3) The electrical conductivity of the fluid changes significantly.

(4) The millivolt signal sent by the electrode has zero drift during the amplification and conversion process.

(5) Subject to external interference.

The quantitative control sewage flow meter will drift during use. How to eliminate the drift of the quantitative control sewage flow meter?

1. Elimination of differential interference and power frequency interference:

Differential interference and power frequency interference signals often coexist in the signal, and it is often difficult to completely filter out the power frequency interference with the low-pass filter in the signal processing circuit. Our company adopts synchronous sampling and power frequency compensation technology to suppress the power frequency interference caused by the mixing of power frequency interference and power frequency power supply frequency fluctuation in the flow signal potential, and effectively eliminate differential interference. In synchronous sampling technology, the sampling start time lags behind the excitation signal by 1/4 cycle, and the pulse width is an even multiple of the power frequency cycle. While eliminating differential interference, the average value of the power frequency interference in the flow signal potential is equal to zero to eliminate the influence of power frequency interference; the frequency fluctuation compensation of the power frequency power supply is to ensure that the excitation power supply and the sampling pulse are adjusted synchronously in the dynamic fluctuation of the frequency, truly realizing synchronous sampling technology and synchronous excitation technology, synchronous A/D conversion, and reducing the influence of differential interference and power frequency interference.

2. Zero drift elimination:

The so-called zero drift means 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 the circuits of each level of amplification. After multiple levels of amplification, it becomes a larger signal at the output end. Since 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 realize the weak signal collection of large internal resistance to suppress the introduction of common mode signals. After the first-level amplification circuit, a DC blocking capacitor is used to filter out the baseline zero drift to prevent the DC signal from being too large and exceeding the input range of the A/D conversion.

3. Other measures to remove interference:

The orthogonal interference generated by the "transformer effect" of the quantitative control sewage flow meter sensor is eliminated by the "transmitter zeroing method". In terms of software design, digital filtering technology, power-off protection technology, and software instruction redundancy measures are used to effectively improve the reliability of the input microprocessor digital.

The above are several methods we have summarized to remove drift. If you have better methods when using quantitative control sewage flow meters, please share them with us. We are very grateful for your cooperation.