Ways to adjust the sensitivity of vortex flowmeter

When the vortex flowmeter has no liquid activity in the pipeline, the receiver counts abnormally because of the noise generated by the pipeline oscillation. At this time, the sensitivity of the external surface should be adjusted.

1.Adjustment of amplifier gain

Under normal circumstances, there is no need to adjust the gain of the vortex flowmeter amplifier unless the sensor is replaced. The amplifier gain is adjusted by the AMP potentiometer on the amplifier board A, and the enlarged eddy current waveform is monitored on the oscilloscope. At the minimum flow rate, the peak value of the eddy current waveform is about 100mVP-P.

2. Adjustment of trigger level

The addition of trigger level (sensitivity of pulse generation) will reduce the sensitivity of flow. When there is no liquid activity in the pipeline, abnormal pulses are formed due to pipeline oscillation and pulsating activity presenting noise, which can be effectively processed by adding a trigger level.

The trigger level can be adjusted by the TRG potentiometer on the amplifier board of the vortex flowmeter. Whenever the peak value of the expanded vortex waveform exceeds the predetermined trigger level, it can be transformed into a pulse. Therefore, because the trigger level is added, the flow sensitivity is reduced.

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

When the sensitivity is changed, the result's minimum flow rate (measurable lower limit flow rate) is approximately 1/(the square root of the sensitivity multiplied by the standard minimum flow rate).

3. Zero point adjustment

Correct wiring of the vortex flowmeter, input a zero fluctuation signal to the vortex flowmeter through the low-frequency signal generator, adjust the zero point to adjust the potentiometer, the display value of the digital multimeter should be 4mA.

4. Adjustment of full scale

If you don’t know the full-scale frequency of the appearance, you can use the maximum flow rate to calculate the full-scale frequency B to adjust the appearance. The relationship is: fmax=KQQmax

Correct wiring, the vortex flowmeter uses the signal generator to output the signal to the charge amplifier, increase the input signal amplitude, transform the output square wave, and change the output frequency of the signal generator until the value displayed on the frequency meter is according to the above formula The calculated full-scale frequency stops. At this time, the fixed frequency remains unchanged, and the range potentiometer is adjusted, and the digital multimeter stops when the display value is 20mA.