Development of Intelligent Flowmeters Through Signal Processing

Abstract

In the current evolution of instrumentation for process control, there is considerable emphasis on the development of ‘smart’ or intelligent instruments. This can be justified from an hierarchical viewpoint because the performance of any control system is very dependent on the quality and integrity of the measurement signals. It can also be justified from a ‘cost of ownership’ viewpoint because it facilitates optimisation of the signal levels for process management and reduces the inventory of spare equipment for maintenance. The present trend in the development of transmitters is to include a microprocessor which optimises the accuracy of measurement, applies self-diagnostic routines and provides means for remote setting of zero and span. The overall design of the transmitters is such that the output signal represents the mean value of the measurand but this does not fully reflect the dynamic response of the sensor to the process. On the other hand, our own research has shown that useful information regarding the status of the process plant can be retrieved by applying well-established signal processing techniques to the basic or unconditioned signals from the sensors. This paper describes how these techniques can be applied to improve the quality of signals available from turbine and vortex flowmeters.