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 mains terminal strip as necessary
Use isolation mat as required
No Demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the AC voltage between the Flame Sense Electrode Lead (Whilst Attached to the Flame Sense Electrode) and the Neutral at the incoming mains terminal block.
Expect approximately 50 VAC