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Several methods for adjusting the sensitivity of vortex flowmeter

When there is no liquid flow in the pipe, the noise generated by the vibration of the pipeline causes the receiver to count abnormally. At this time, the sensitivity of the meter should be adjusted.

1, amplifier gain adjustment
In general, it is not necessary to adjust the gain of the vortex flowmeter amplifier unless after the sensor is replaced. The amplifier gain is adjusted by an AMP potentiometer on amplifier board A, and the amplified eddy current waveform is monitored on an oscilloscope. At the minimum flow rate, the peak value of the eddy current waveform is approximately 100 mVP-P.

2, the trigger level adjustment
An increase in the trigger level (sensitivity of the pulse generation) reduces the sensitivity of the flow. When there is no liquid flowing in the pipe, due to the vibration of the pipeline, noise occurs in the pulsating flow, and abnormal pulse generation can be effectively processed by increasing the trigger level.

The trigger level can be adjusted by a TRG potentiometer on the vortex flowmeter amplifier board, and the peak of the amplified eddy current waveform can be converted into a pulse whenever it exceeds a predetermined trigger level. Therefore, the flow sensitivity is reduced by increasing the trigger level.

When the trigger level 80mVP-P is changed to 350mVP-P, the sensitivity of the result will be 80/350=1/4.4 (sensitivity ratio) times.

When the sensitivity is changed, the resulting minimum flow (measurable low limit flow) is approximately 1/(the square of the sensitivity is multiplied by the standard minimum flow).

3, zero adjustment
The vortex flowmeter is correctly wired. The low-frequency signal generator is used to input a signal with a zero amplitude to the vortex flowmeter. The zero-point adjustment potentiometer is adjusted. The display value of the digital multimeter should be 4 mA.

4, full scale adjustment
If you do not know the full-scale frequency of the meter, you can use the maximum flow rate to calculate the full-scale frequency B to adjust the meter. The relationship is: fmax=KQQmax

For correct wiring, the vortex flowmeter uses a signal generator to output a signal to the charge amplifier, increase the amplitude of the input signal, convert the output square wave, and change the output frequency of the signal generator until the value displayed on the frequency meter is calculated according to the above formula. The full-scale frequency is up. At this time, the fixed frequency does not change, and the range potentiometer is adjusted, and the value of the digital multimeter is 20 mA.

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