Portable Ultrasonic Flow Meter

A portable meter answers a question rather than billing a customer: is the pump delivering what it should, does the district meter agree with the treatment works, where is the water going between two points. It is carried to the pipe, clamped on for the length of the test and taken away again.

The handset works on the transit-time principle with a pair of clamp-on transducers. They can be mounted in V mode, where the signal crosses the pipe twice; in W mode, four times, for small bores; or in Z mode, on opposite sides of the pipe, once, for large bores or difficult liquids. The arrangement is chosen at the pipe to suit its size and the liquid. The M1 transducer is standard and three other models are optional; the transducer cables are 2 × 10 m as standard and up to 2 × 500 m to order.

Accuracy is ±1% of reading at velocities above 0.2 m/s, with 0.5% linearity and 0.2% repeatability, over a velocity range of ±32 m/s. Pipe sizes run from 20 to 6,000 mm, and the meter reads virtually any liquid. Three 7-digit totalisers hold net, forward and reverse flow separately, a fourth can be started and stopped from the keypad for a timed calibration run, and the response time can be set anywhere from 0 to 999 s.

The handset is an ABS case of 100 × 66 × 20 mm weighing 514 g with its batteries, with a 4 × 16 character display. Three built-in rechargeable AAA batteries give more than ten hours of operation. A built-in logger stores over 2,000 lines of data, the setup can be locked behind an access code, and an RS-232C port running at 75 to 57,600 baud lets the meter be read, or operated key by key, from a computer.