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1. How to adjust the sensitivity of a vortex flowmeter correctly
The core method for adjusting the sensitivity of a vortex flowmeter is to change the gain of the detection electrode or adjust the amplification factor of the signal processing circuit, which needs to be calibrated with the K coefficient. 1. Electrical parameter adjustment • Detection of electrode gain: Adjust the preamplifier gain (usually adjustable by 0.5-10 times the gain) in the converter settings interface, and the sensitivity will increase by about 6dB for every 1-fold increase in gain. • Signal filtering threshold: Set the cutoff frequency of the low-pass filter to 1.5 times the frequency corresponding to the highest flow rate of the medium (for example, 30Hz for a water medium with a flow rate of 2m/s). 2. Mechanical parameter calibration • K coefficient correction: According to the latest JJG 1030-2022 standard, when using the weighing method for calibration, the instrument coefficient calculation formula is K=Qm/(f × ρ), where Qm is the mass flow rate (kg/h), f is the pulse frequency (Hz), and ρ is the medium density (kg/m ³). 3. On site debugging steps: ① Perform zero calibration under air traffic control conditions (error should be less than 0.5% FS) ② Introduce a medium with a range of 20%/50%/100% and record the output frequency at each point. Use the least squares method to fit a three-point calibration curve (with a linearity level of 0.2). Precautions: - After adjustment, EMC testing needs to be repeated (with a minimum RF field immunity of 10V/m). - When the medium temperature changes by more than 10 ℃, recalibration is required. - Electrode contamination can cause sensitivity to decrease by more than 15%, and regular cleaning
2. What flow meters are used for CNG filling measurement?
CNG filling measurement mainly uses three types: turbine flow meters, vortex flow meters, and Coriolis mass flow meters. 1. The turbine flowmeter adopts the principle that the turbine speed is proportional to the flow rate, with high accuracy (± 0.5% - ± 1%), good repeatability, and wide range ratio (10:1 to 20:1). However, it requires high fluid cleanliness, and impurities may block the virtual wheel and cause measurement errors.
Pressure and other parameters have an impact, but the equipment cost and installation requirements are relatively high. All three types of flow meters must comply with the requirements of the national standard GB/T 32201-2015 Gas Flow Meter. The actual selection needs to be comprehensively evaluated based on accuracy requirements, fluid characteristics, and budget.
3. How to calibrate the zero point of a vortex flowmeter
The zero point calibration of a vortex flowmeter needs to be achieved through signal adjustment in the empty tube state, and the specific operation needs to be selected according to the sensor type. Mechanical calibration steps - Ensure that the pipeline is completely emptied and the fluid is stationary - Use a special tool to adjust the mechanical zero adjustment screw on the sensor housing until the output signal is stable at 4mA (analog signal) or 0m ³/h (old backup digital display) - For split structure, synchronously check the zero position potentiometer of the preamplifier 2 Electronic Calibration Method - Enter the zero calibration menu through the HART communicator or on-site operation interface - The new intelligent instrument supports automatic zero tracking
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