A low-water cut-off system [A] determines if fluid [W] within a boiler [16]
or other enclosure drops below a predetermined level within the enclosure. A signal
generator introduces a signal into the enclosure so that the signal is present
for sensing at the predetermined level, where a probe [14] is provided for
sensing the signal if present as occurs if the water is at the predetermined level.
A control [18], which includes a microcontroller [25], is responsive
to the probe for providing a control function in response to whether the signal
is so sensed by the probe, and so to determine if water has dropped below the predetermined
level. The function may be causing alarm signalling or boiler heating cut-off.
Self-test and time delay features are also included. Provision is made so that
the control compensates for variation in electrical conductivity of the water through
which the probe signal is sent.
