Dynamic Offset Correction of Electromagnetic Flowmeters

This contribution addresses the electrochemical voltage drift of electromagnetic flowmeters. We will extend the conventional discrete time alternating field method to continuous operation. A Kalman filter, based on a state space model of the sensor, will be developed to separate the flow-proportional signal from the noisy voltage drift of the electrodes. The new algorithm facilitates the processing of flow information rarely used today, i.e., longer intervals of the electrode voltage during times of stable magnetic field. The actually processed time interval of the electrode signal will be extended considerably. Thereby, a lower energy consumption and an increased accuracy can be achieved. The measurement error of the new method will be demonstrated to be less addicted to temporal flow variations. Measurements show a similar accuracy, but with a significantly reduced energy demand. A prototype with a field offset provided by permanent magnets is set up to evaluate its energy consumption. Offline signal processing predicts an 80% lower power demand compared to conventional flowmeters.