Principles of drawing
• Check the incoming supply voltages first
• Check for voltages at the specific test points in circuit (as per manufacturers test point data sheet)
• Do dead test of circuit for integrity of protection devices and others
• In dead test, check for continuity of circuits, as intended, and check for insulation resistance
• If it’s not possible to perform a dead test, connect the supply to the circuit and do a live test of circuit.
Generally, any electrical circuit can be differentiated in two sections:
• Power circuit
• Control circuit.
It is always advisable to first check the power circuit. So, if the power circuit works, as it should, then troubleshoot the control circuit.
Power circuit check list:
• Incoming power to circuit and its integrity
• Check for correct functioning of protection devices
• Check visual cable continuity
• Check for any signs of flash or burning smell of devices.
Control circuit check list:
• Control circuit power first
• Check for proper functioning of relays, timers, and switches
• Check visual cable continuity
• Check for wire interconnections and terminal connections of circuit
• Check logical operational sequence of contactor switching
• Check for timer duration settings.
If the above criteria are checked and still the motor (final device) is not working, then test the motor (final device).
Meters used in troubleshooting:
• Multi-range voltmeters
• Clip-around or clamp-on ammeters
• Electrostatic voltmeters (high-voltage measurements)
• Multimeter or volt-ohm-milli-ammeter (voltage, resistance, current, etc.)
• Thermocouple meters (indirect current measurement)
• True wattmeters (directly measurement of power in watts)
• Pseudo wattmeters
• Digital voltmeters
• Heterodyne wavemeter (analog measurement of frequency)
• Digital frequency meters
• Continuity testers
• Analog ohmmeters
• Digital ohmmeters
• Insulation testers
• Digital capacitance meters
• Q meter (measuring inductance and capacitance)
• Oscilloscope (measuring wave forms, amplitude, frequency, phase, etc.)
• Dip meter (radio frequencies)
• Logic level probe testers
• Logic analyzers (diagnosing logic systems problems)
• Spectrum analyzers.
