One of the assumptions made when installing a flowmeter is that the instrument is placed there where the flow is stable and undisturbed. In reality, however, such ideal measurement conditions hardly ever occurs.

Disturbed flow profiles could be caused by numerous things but generally are a result in a change to the pipe through which the liquid is flowing. This could be a change of angle or plane through bends, a change of diameter through a reducer or diffuser or some other process equipment such as a valve or pump. These changes in fluid condition cause the flow profile to shift with the point of maximum fluid velocity no longer being located in the center of the pipe.

Dual channel flowmeters for the best results

Several of our clamp-on ultrasonic flowmeters have the possibility of connecting two pairs of sensors at the same time. This gives the option of either measuring two pipes at the same time, or alternatively mounting two sets of transducers on to the same pipe.

There are two situations in which a dual channel flow measurement can be an advantage :
• When the disturbed flow profile may be caused by bends in the pipe or restricted flow.
• When there is a need for higher accuracy.

N.B. When using a dual channel flowmeter – as well as many other devices – the complete flow profile must always be taken into account. Determining a suitable location for installing the measuring equipment is essential.

Guidelines for dual-channel flow measurement

How dual channel ultrasonic flowmeters can be used to improve measurement results under non-ideal installation conditions is described in this downloadable document.