Factors affecting the work of vortex flowmeter

The measurement range of the vortex flowmeter is relatively large, generally 10:1, but the lower limit of measurement is limited by many factors: Re>10000 is the most basic condition for the vortex flowmeter to work. In addition, it is also limited by the vortex energy. If the flow rate is low, the strength and rotation speed of the vortex are also low, and it is difficult to cause the sensing element to generate a response signal. The vortex frequency f is also small, and the signal processing will also cause the measurement range of the vortex flowmeter to be larger, generally 10:1. However, the lower limit of measurement is limited by many factors: Re>10000 is the most basic condition for the vortex flowmeter to work. In addition, it is also limited by the vortex energy. If the medium flow rate is low, the strength and rotation speed of the vortex are also low. It causes the sensor element to generate a response signal, and the vortex frequency f is also small, which also makes signal processing difficult. The upper limit of the measurement is limited by the frequency response of the sensor (for example, the magnetic sensitive type generally does not exceed 400Hz) and the frequency of the circuit. Therefore, the flow rate range must be calculated and accounted for during the design, and the selection should be made according to the flow rate of the fluid. The environmental conditions at the use site are complicated. In addition to the environmental temperature, humidity, and atmosphere, electromagnetic interference should also be considered when selecting models. In strong interference, such as high-voltage power transmission stations, large-scale rectifier stations, etc., magnetic sensitive, piezoelectric stress type and other instruments cannot work normally or cannot accurately measure.　　The temperature of the medium also has a great influence on the performance of the vortex flowmeter. For example, the pressure stress type vortex flowmeter cannot be used for a long time at 300℃, because its insulation resistance will drop from 10MΩ～10MΩ at room temperature to 1MΩ～10KΩ, and the output signal will become smaller, which will deteriorate the measurement characteristics. Magnetic sensitive or capacitive structure should be selected. In the measurement system, the sensor and the converter should be installed separately to prevent long-term high temperature from affecting the reliability and service life of the instrument.　　 Vibration is also a big enemy of this type of instrument. Therefore, pay attention to avoid mechanical vibration, especially the transverse vibration of the pipe (vertical to the pipe axis and vertical vortex to generate the vibration of the body axis). This effect cannot be suppressed and eliminated in the flowmeter structure design. Since the vortex signal is also sensitive to the influence of the flow field, it is not suitable to use when the length of the straight pipe section cannot guarantee the necessary flow conditions for stable vortex street. Even the capacitive and ultrasonic types with strong vibration resistance can not be ignored to ensure that the fluid is a fully developed unidirectional flow.