An EESIFLO EASZ-10FP consists of two sensor housings which contain ultrasonic transducers . The transducers are positioned on one side of the pipe or tube . The flowmeter's electronic ultrasonic circuitry directs signals from one transducer to another and back through an upstream and a downstream measurement cycle.

The flowmeter derives an accurate measure of the "transit time" it took for the wave of ultrasound to travel from one transducer to the other. The difference between the upstream and downstream integrated transit times is a measure of velocity .

Upstream Transit Time Measurement Cycles

An electrical excitation causes the downstream transducer to emit a wave of ultrasound. From these signals, the flowmeter derives an accurate measure of the "transit time" it took for the wave of ultrasound to travel from one transducer to the other.

Downstream Transit Time Measurement Cycles

The same transmit-receive sequence of the upstream cycle is repeated, but with the transmitting and receiving functions of the transducers reversed so that the liquid flow under study is bisected by an ultrasonic wave in the downstream direction. Again, the flowmeter derives and records from this transmit-receive sequence an accurate measure of transit time.

Just as the speed of a plane is affected by headwinds and tailwinds, the transit time of ultrasound passing through a conduit is affected by the motion of liquid flowing through that conduit. During the upstream cycle, the sound wave travels against flow and total transit time is increased by a flow-dependent amount. During the downstream cycle, the sound wave travels with flow and total transit time is decreased by the same flow-dependent amount. The EESIFLO EASZ 10FP flowmeter subtracts the downstream transit time from the upstream transit times utilizing shear wave ultrasonic signals. This difference of integrated transit times is a measure of volume flow.