Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to mVolts DC 
Attach +ve probe of multimeter to a suitable earth point via crocodile clip
Gas On
Gas On
Measurement:
Depress gas valve control knob and ignite pilot.
Whilst keeping gas valve depressed, place -ve probe on the thermocouple where it connects with the interrupter plate, measure voltage produced by the thermocouple.
Whilst keeping gas valve depressed, place -ve probe on the thermocouple where it connects with the interrupter plate, measure voltage produced by the thermocouple.
Isolate as per TOPs P4
and refit as necessary