Dulas Solar VC150, Handbook

Page: 51 / 156

51
3.
RESISTANCE
In fault finding and repairs of photovoltaic refrigerator systems it is necessary to
measure the electrical resistance of the compressor windings and to determine if
these windings are adequately insulated. The millimeter provided in the UNIPAC
maintenance kit (or any other millimeter) is adequate for these tasks if the following
procedure is observed.
1.
Switch OFF the refrigerator.
2.
Disconnect the wires from the positive terminal of the battery.
3.
Set the millimeter to measure resistance.
4. (a) If you want to measure small values of resistance, set the range on the
millimeter to ‘one ohm’ (which may be indicated 1)
(b) If you want to measure high values of resistance set the range to 100,000
ohms or the largest range of resistance on your millimeter.
5. Switch ON the meter, plug in the meter leads to the correct sockets in the meter,
and hold the tips of the probes together.
6. If you have an analogue meter adjust the meter so that the resistance between
the probes reads zero. If you are unable to adjust the meter so that it reads zero,
this means that the batteries in the meter are discharged and should be changed.
7. Holds the probes between the two points in the circuit where you want to measure
resistance.
8. Read the resistance value directly on the meter if you have a digital meter, or on
the appropriate scale if you have an analogue meter.
9. SWITCH THE TIMER METER OFF when you have finished.