I have an "older" Amprobe 6-600VAC Circuit Tracing Kit (older = purchased new in 1996).
The Transmitter pulses an Audio Frequency of apx.4.0kHz, with an Octave or Two on each side (1k, 2k, then 8k, 16k), at 250ms intervals (250ms on, then 250ms off, in a continuously repeating cadence).
The Audio Information is "Carried" on the 60Hz of the Branch Circuit under test (typical "Carrier Current" Modulation of the 60Hz Power Circuit).
Kit may be used on Energized or De-energized Circuits, with the Transmitter connected as follows:
a.: Directly for 300VAC and less Energized Circuitry,
b.: Through a 2:1 Step-Down Transformer, for Energized Circuits of >300VAC to 600VAC,
c.: Connected via 9VDC Drycell for De-energized Circuitry (no Loads connected to Circuit).
Trick #1:
(Beginning with the Receiver set for Tracing at the Conductor, first on the lowest sensitivity, moving to the highest sensitivity)
If the Energized Circuit under test contains either a Back-Up Battery Ballast, or Stand-Alone UPS, the Pulsed Audio Frequency will be noticeably distorted.
Half-Steps between Octaves are very noticeable, and the Amplitude of the Audio Fundamental 4.0Khz Tone is noticeably increased - as much as 140% the normal Amplitude.
When the Circuit does not resonate back through the Bus, into a Branch Circuit that has nearly similar XC, the Distorted Tone is strong only on the Circuit being tested.
When another Circuit is resonated, the signal strength is equally high on all effected Circuits.
To determine the tested Circuit, place the Receiver on the "Breakers" Selection, with the sensitivity set high.
Perform test on all Breakers with the Tone.
Turn Receiver 90° Left, then 90° Right.
Correct Circuit will remain high level throughout the turning, whereas the others will drop Amplitude.
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Trick #2:
Where Two or more Branch Circuits are showing similar Levels on the receiver (non-distorted signals), connect a suitable Load to the Circuit (at the Transmitter end), then look for that Load via Clamp-On type Ammeter.
Connecting an intermittent Load - such as a Flashing Lamp, will assist greatly if the Circuit being tested has randomly changing connected Loads.
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"Trick #3"...
(Not necessarily a Circuit Tracing tip, but still worth mentioning)
When using a High Input Z Voltmeter (i.e.: DVM) on Circuits with high levels of Capacitive Coupling effects (long L-N Circuits, or any types of Ungrounded Systems measured L-G), connect a Solenoid-Type Low Input Z Meter; such as a "Wiggy", "Vol-Test", or "Vol-Con", in Parallel with the Hi Z Meter, to Load the Circuit for an accurate reading.
I am sure there are several others, just can't think of any more right now!!!
--Scott (EE)
