Hawker Electronics were approached to solve a problem monitoring the water levels in Combined Sewerage Overflows - CSOs - especially low and high levels, to prevent flooding.

Hawker Electronics were approached by a well known International Water Company who had a small problem. They wanted to monitor levels in Combined Sewerage Overflows or CSOs as they are better known, especially low and high levels. They had conducted trials with floats for very low levels and found that the float was too large for the application.

They also found that at high levels turbulence caused erratic movement of the float.

Hawker Electronics demonstrated that their electrode system had no moving parts to tangle up or wear out.

Trials were conducted with the Hawker 'Alarum', which is a compact electrode holder with an integral electronic circuit.

The circuit is very low voltage, operating from 24 v DC, and has such low power requirements that it can run from a solar panel or batteries.

A 24v DC 12A/H battery will power it for around 600 hours.

The Alarum had originally been designed for alarms in remote areas or in containment sumps and bunded areas.

Following extensive trials two modifications were requested.

The electrodes needed to be more substantial for higher flows and the unit needed to be ATEX approved for Intrinsically Safe applications demanded by CSOs.

The first requirement was straightforward.

The second one was more demanding but with the Hawker experience in Intrinsically Safe approved equipment and their background in sewage applications, ATEX approval was achieved in just over 3 months.

CSO monitoring can now provide advance warning of high water levels, signalling into the water company warning systems monitoring potential flood situations in urban areas.