Abstract: A method and apparatus for increasing the resolution and accuracy of flow measurements made by vortex flowmeters through the use of an adaptive filter. A vortex sensor signal is conditioned by a bandpass filter whose corner frequencies are dynamically altered as a function of the measured frequency of the vortex sensor signal. When the change in frequency is relatively small, the filters' corner frequencies are set to track the frequency signal in accordance with a specified bandwidth thereby improving the signal-to-noise ratio. For large frequency changes, a new frequency signal is searched for thereby avoiding tracking erroneous noise signals. Furthermore, compensation for additional or missed vortex pulses is made thereby generating a more accurate vortex frequency measurement.

Abstract: An analog isolation circuit for providing electrical isolation between interrelated electrical circuitry contained within a vortex flowmeter. The circuit provides a low power and low cost solution to the problem of ground isolation presented in flowmeters utilizing grounded sensors which generate low frequency sinusoidal signals. A pair of clock-controlled analog switches couples the voltage difference between two successive samples of an analog signal across an isolation barrier. The operation of the switches at a low frequency rate and with a short sampling interval while utilizing a low magnetizing current preserves the magnitude of the input waveform while consuming approximately 1 mW of power.