responds: In my opinion, the only dependable
way to detect live current — the way I
would want to bet my life on — is with a
multimeter connected to the wires. Check the
voltage, conduit to ground, ground to hot, ground
to neutral, and neutral to hot.
The wands, or "sniffers," I've used —
the types you wave over the wires to tell you
whether they're hot — have not been
dependable. I have had many that gave false
Regarding wires in conduit, you must remember
that the conduit may be grounded, which would give
a "dead" reading when the wires inside are hot.
Another problem with low-cost voltage sensor pens
is that many don't detect voltages of less than 60
volts. Thus, if there is a low-voltage circuit or a
circuit making intermittent contact, the sensor
won't pick it up.
One unit that I have not tried but that looks
promising is made by Extech Instruments of Waltham,
www.extech.com). Their model
DVA30 ($39 on the web) is claimed to measure from 5
to 250 VAC through conduit or shielded wire.
Rex Cauldwell is a master electrician in
Roanoke, Va., a frequent contributor to JLC, and
the author of several books, including Wiring a