Transient process based electromagnetic flow measurement methods and implementation

The ordinary electromagnetic flowmeter (EMF) utilizes the steady-state period of the excitation current for measuring the flow rate in order to ensure zero stability and measurement accuracy. In this paper, the transient process of EMF is studied to measure the flow rate so as to realize applications requiring ultra-low power consumption, for example, water meters. For this reason, the dynamic excitation current and signal voltage of the transient process are analyzed, and three kinds of transient measurement methods are proposed to determine the relationship between the processing results of the signal voltage and flow rates. They are the voltage-current ratio method, voltage-current differential method, and differential interference compensation method. In order to verify these measurement methods, a DSP (Digital Signal Processor) that is the same processing chip as the current ordinary electromagnetic flow transmitter is selected to design a hardware system of the transmitter, and the excitation current and signal voltage of the transient process are acquired. Analysis of experimental data shows that there is a good linear relationship between the processing results of the signal voltage and flow rates. The software of the electromagnetic flow transmitter based on DSP is developed, and the transient measurement methods are realized in real time so as to perform the water flow calibration experiments and power consumption tests. The experimental results show that the measurement accuracy is 0.5% which is the same as the ordinary EMF. Comparisons of power consumption show that the excitation power consumption of EMF based on the transient measurement principle is 1/1200 of that of the ordinary EMF.