A radically new dynamic response capability for Coriolis flow meters

The dynamic response of flow meters is significant in many applications, including fast control operations, e.g. short duration (less than 1 s) batch filling and for tracking the periodic flow fluctuations produced by positive displacement devices. The factors which determine Coriolis dynamic response have been elucidated. It has been shown that the meter flow tube response time cannot be less than the duration of one drive cycle of the tube vibration (i.e. reciprocal of drive frequency). This gives the potential of a response time of order 1 ms for the fastest currently available meters. However, the delay-time and update rates from the user output depend upon flow transmitter technology and design. Flow tube dynamic response has been investigated theoretically (simple straight tube), by finite element simulation (complex flow tube shapes) and experimentally. Commercially available meters were tested to determine the flow tube dynamic response to step changes in flow rate and the response to low frequency (compared with meter drive frequency) flow pulsations. Generally, dynamic flow events have been found to introduce contaminating signal components at one or more frequencies, other than that of the meter drive. The paper also presents details of the signal processing used to extract the required phase-difference and a method for reducing the contaminating signal noise. A new fast-response meter is currently being developed and some of the significant advances in the technology of a novel digital transmitter are described.