DETECTION OF ZERO SHIFT IN CORIOLIS MASS FLOWMETERS

K. Kolahi, R. Storm, H. Röck

Abstract

Coriolis mass flowmeters (CMF) are claimed to be not affected by the properties of the liquid such as heat conductivity, heat capacity and viscosity. They are direct mass flowmeters and form a real mean along the flow profile. However, there is some evidence from field applications that the devices, in particular with single straight pipe, suffer under the null drift. Therefore, the zero shift must be adjusted to the properties of liquid, installation site and operating conditions. The zero shift is caused by asymmetry of the oscillating system. A change in the asymmetry leads to the zero shift. This paper presents two methods to determine the zero shift: a sensor and a model based approach. The first uses additional acceleration sensors to measure the vibration of the straight pipe’s mounting. The motion of the mounting represents asymmetries in dissipation. The second method utilizes a model which includes the asymmetries as parameters. These can be detected by auxiliary exitation of the oscillating system.

Keywords

Coriolis mass flowmeter, accuracy, zero shift

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IMEKO-WC-2000-TC9-P241.pdf

DOI

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IMEKO TC

TC9 - Flow Measurement

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