Magnetic flowmeter with flow independent autozero estimation

Abstract

A magnetic flowmeter includes at least one coil configured to generate a magnetic field within a process fluid flow. A pair of electrodes is configured to detect an electromotive force within the process fluid flow in response to the magnetic field. Coil drive circuitry is coupled to the at least one coil and is configured to cause the at least one coil to generate the magnetic field. Measurement circuitry is operably coupled to the pair of electrodes and configured to provide an indication of the detected electromotive force. A processor is coupled to the measurement circuitry and the coil drive circuitry. The processor is configured to cause the coil drive circuitry to operate at one of a plurality of coil drive frequencies. The processor is also configured to obtain a plurality of measurement samples while process fluid is flowing and while the coil drive circuitry is operating at a first frequency. The processor is configured to generate an autozero estimate for operation at a second coil drive frequency higher than the first coil drive frequency and to save the autozero estimate for use during operation at the second coil drive frequency.