Transit time technique

When ultrasound is transmitted through a liquid the speed at which the sound travels is accelerated slightly when transmitted in the same direction as the liquid flow and

decelerated slightly when transmitted against it. The difference in time taken by the sound to travel over the same distance but in opposite directions is therefore proportional to the flow velocity of the liquid and can be used to calculate the flow rate.

Transit time technique

This technique is known as ‘transit time’ measurement and is the method used by the Portaflow PT 500/400 or 330/220 system to calculate the liquid flow rate. Once the flow velocity is known it is a simple matter for the Portaflow PT 500/400 or PF330/220 to calculate the volumetric flow.

Operating modes

The Portaflow sensors can be set to operate in one of four modes determined mainly by the pipe diameter and the transducer set in use.

In practice, the Portaflow PT 500/400 or PF330/220 determines the operating mode and calculates the appropriate transducer separation distance in response to site application data entered by the user.