Several methods for adjusting sensitivity of vortex flowmeter

1. Adjustment of amplifier gain

In general, there is no need to adjust the gain of the vortex flowmeter amplifier unless the sensor is replaced. Adjust the amplifier gain through the AMP potentiometer on amplifier board A, and monitor the amplified eddy current waveform on the oscilloscope. At low flow rates, the peak value of the eddy current waveform is approximately 100mVP-P.

2. Adjustment of trigger level

The increase in trigger level (sensitivity of pulse occurrence) will reduce the sensitivity of flow rate. When there is no liquid flow in the pipeline, abnormal pulse occurrence caused by pipeline vibration and pulsating flow noise can be addressed by increasing the trigger level.

The TRG potentiometer on the amplifier board of the vortex flowmeter can adjust the trigger level, and the peak value of the amplified vortex waveform can be converted into a pulse whenever it exceeds the predetermined trigger level. Therefore, by increasing the trigger level, the flow sensitivity will decrease.

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

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

3. Zero point adjustment

The correct wiring of the vortex flowmeter is to input a signal with zero amplitude to the vortex flowmeter through a low-frequency signal generator, adjust the zero point adjustment potentiometer, and the display value of the digital multimeter should be 4mA.

4. Full range adjustment

If the full-scale frequency of the instrument is not known, the instrument can be calibrated by calculating the full-scale frequency B through * * flow rate,

Correct wiring: The vortex flowmeter uses a signal generator to output a signal to the charge amplifier, increases the input signal amplitude, converts the output square wave, and changes the output frequency of the signal generator until the value displayed on the frequency meter is the full-scale frequency calculated according to the above formula. At this point, keep the fixed frequency constant and adjust the range potentiometer until the reading on the digital multimeter reaches 20mA.