Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Gain access to detection electrode connection
Ensure No demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Cancel purge cycle & if required, reset boiler.
Measure for A/C voltage between the detection electrode connection and a suitable earth.
Expected voltage approximately 89 vac.