Patent ID: 8571819

Claim:
A Coriolis flowmeter comprising: a flowtube having a fluid flowing therethrough, the flowtube being subject to a vibration, the vibration of the flowtube comprising at least a drive mode of vibration and a contaminant mode of vibration; a sensor for outputting an observed signal representative of the vibration of the flowtube, the observed signal including a drive mode signal corresponding to the drive mode of vibration and a contaminant mode signal corresponding to the contaminant mode of vibration; and, a transmitter for receiving the observed signal and determining a parameter of the fluid, the transmitter comprising: a zero-crossing detector for detecting a plurality of observed zero-crossings of the observed sensor signal; a frequency calculator operable to determine an observed signal frequency and an initial estimate of frequency of the contaminant mode signal, the observed signal frequency and the contaminant mode signal frequency being used to determine a parameter of fluid passing through the flowmeter.