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The vortex flow meter is a relatively precise flow measurement instrument. Its working principle is the process of converting Karman vortex street signals into flow data, from the measurement sensor to the flow amplifier. During use, it sometimes happens that the vortex flow meter is powered, but no flow rate is displayed on the LCD screen, while a flow rate value is shown on the remote transmission signal. When such a fault occurs, we need to conduct inspections from the following aspects. 1. After the instrument is powered on, the valve does not open, yet a signal is being generated. ① The signal output from the sensor of the vortex flow meter is blocked, or external electromagnetic interference is present in the grounding of the flow meter ； ②During installation, there is electromagnetic interference generated by large mechanical and electrical equipment or high-frequency devices around the instrument ； ③The pipeline in which the vortex flow meter is installed experiences severe vibrations ； ④The sensitivity of the sensor to receive signals is too high ； To address these faults, appropriate measures should be taken, including enhancing the shielding and grounding against external interference, strengthening the pipes to eliminate vibrations, and adjusting the sensors to reduce their sensitivity ； 2. The power supply of the intermittent-operating vortex flow meter remains connected, and a signal is still generated even after the valve is closed. This type of fault is similar to the previous one; its causes are mainly pipe vibrations or external electromagnetic interference, and the solutions are the same as those mentioned above. 3. When the instrument is powered on, the signal output for closing the upstream valve is zero, while the signal output for closing the downstream valve is not zero. The cause of this type of fault is mainly due to the pulsating pressure of the fluid upstream. When the vortex flow meter is installed on a T-shaped branch pipe, and there are pressure fluctuations in the upstream main pipeline, or if there is a source that generates pulsating pressure, then false signals will be produced as a result of these pressure fluctuations. Solution: The valve located downstream needs to be installed upstream of the vortex flow meter; during shutdown, the upstream valve can be closed to isolate pulsating pressures, provided that there is a sufficient straight pipe section distance from the instrument ； 4. When the power is on, the signal output for closing the upstream valve is not zero; it becomes zero only when the downstream valve is closed. This type of fault is caused by fluid disturbances within the pipeline. Generally, in pipelines where the straight section downstream of the vortex flow meter is short and its outlet is close to other valves, these fluid disturbances can reach the sensing elements of the vortex flow meter, resulting in false signals ； Solution: It is necessary to increase the length of the straight pipe section ahead of the instrument in order to eliminate the faults caused by fluid disturbances. After resolving the above issues, how can the sensitivity of the vortex flow meter be adjusted? 1. Adjustment of the trigger level Increasing the trigger level (the sensitivity at which pulses are generated) reduces the sensitivity to flow rate. When there is no liquid flow in the pipeline, abnormal pulses caused by noise from pulsating flow due to pipeline vibration can be effectively addressed by increasing the trigger level. The trigger level can be adjusted using the TRG potentiometer on the vortex flowmeter amplifier board; whenever the peak value of the amplified eddy current waveform exceeds the predetermined trigger level, it is converted into a pulse. Therefore, as the trigger level increases, the flow sensitivity decreases. 2. Zero adjustment: For proper wiring of the vortex flow meter, a signal with an amplitude of zero is sent to it using a low-frequency signal generator; the zero adjustment potentiometer is then adjusted so that the reading on the digital multimeter is 4 mA. With the correct wiring, the vortex flow meter uses a signal generator to send a signal to the charge amplifier, thereby increasing the amplitude of the input signal and converting it into a square wave. The output frequency of the signal generator is adjusted until the value displayed on the frequency meter corresponds to the full-scale frequency calculated using the above formula. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/20175239314754.jpg