Electromagnetic Flow Sensor Based On The Hall Effect

Hall effect electromagnetic flow sensor can measure the velocity of flow bymeasuring the charge in the moving fluid vertical magnetic field.And the value ofmeasure is determined by the voltage on the plate which is vertical the direction of thecharge movement and magnetic field, where the direction of the charge movement andmagnetic field is vertical too. Compared with the conventional electromagnetic the flowsensor has no moving parts in its internal, so it has a simple and reliable structure withhigh sensitivity and wide range. But hall voltage signal that gets from the sensor is DCsmall signal and affected by the polarization voltage. Therefore, solving the problem ofdc small signal is the key to this project under the polarization voltage. For this reason,an signal processing circuit is needed to modulate first and then demodulate. It cansolve the problem of hall voltage signal amplification and better eliminate polarizationvoltage impact on measurement. The system circuit uses MCU STC12C5A60S2tomake up of the detection circuit. This SCM uses built-in A/D converter to signalconversion for demodulation. For different conductivity fluid, the relationship betweenhall voltage and flow requires the calculated coefficient K to be compensated afterexperiment. And then display the rate of the corresponding flow through LCD1602calculating.The flow calibration using the electrical conductivity is0.01S/m solution byvolume/method0.200m3/h~0.800m3/h to select seven different velocity of flow.Compared with the calibration value, the actual measurement error of the senor flow is<1%with the flow measurement range of0~0.800m3/h. Again from the electricalconductivity of0.01S/m~20S/m within the scope of selected seven different electricalconductivity of the solution, measure the corresponding hall voltage in the seven groupvelocity under the same condition. The ratio of different conductivity of fluid flow andthe hall voltage will be got from measurement of their corresponding dates through Matlab dating fitting. The measured fluid conductivity required in0.01S/m~20S/min the range, when the electrical conductivity is1S/m, the hall voltage measurement isthe maximum.