Scottish Water uses Halma Water
Management’s (HWM’s) SonicSens
ultrasonic level sensor extensively to
monitor flow rates in a variety of
situations including siphon
chambers, Combined Sewer
Overflows (CSOs), overflow and
storm tanks, weirs, reservoirs and
compensation channels. It is a noncontact,
highly accurate level sensor
and flow meter.

The technology behind the noncontact
ultrasonic level sensors uses
an inaudibly high-frequency sound
wave, which is emitted towards the
surface to be measured. The surface
reflects the wave back, and the time
taken for the reflected wave to return
is in direct proportion to the
intervening distance. So, with a
known total distance between the
sensor and the bottom of the vessel
or channel, the depth of the water is
found by simple subtraction.