March 2018 15
Veterans of broadcast and high voltage
applications may refer to something called a “chicken
stick” or “grounding stick.” Figure 1A shows a typical
commercial model. To use the stick, turn off the
equipment and wait for 30 seconds to one minute (or
for as long as metering shows significant voltage is
present). This allows charged capacitors to be drained
by bleeder resistors (high-value resistors connected
directly across the capacitors). If practical, disconnect
the power source for the equipment and insure it can’t
be turned on again while you’re working on it.
Once the meters show the
power supply capacitors have
discharged, open the equipment and
attach the stick’s ground lead to the
power supply common. (Common
is usually but not always the metal
enclosure — don’t assume that it
is; verify first.) Put on some safety
glasses — just in case. Holding the
stick by the insulated portion (never
hold the ground lead in your fingers),
touch its tip to every point in the
circuit where voltage can be present.
Only then is the equipment safe to
If you don’t have a grounding
stick, you can make one as shown in
Figure 1B. Note that the ground lead
is attached outside the PVC tubing.
(Dry wood, fiberglass, or plastic rod
will also work.) The ground wire
should be extra heavy (#8 AWG
or larger) because it might have
to withstand high current when a
fully-charged capacitor is discharged.
Shorting out that charged capacitor
you thought was discharged will
certainly get your attention!
Another surprise to hobbyists
is that voltmeters themselves can
be a source of danger. A maximum
voltage rating is printed on your
meter (see Figure 2). Heed it! That
is the maximum voltage the probes,
connectors, and body of the meter
can withstand. A higher voltage may
PRACTICAL TECHNOLOGY FROM THE HAM WORLD
Post comments on this article and find any associated files and/or downloads at
n FIGURE 1A. This is a commercial grounding stick. The handle is a phenolic
resin rod approximately two feet long. The bottom drawing (B) shows how to
build your own grounding stick. Be sure the ground wire is outside the handle,
and use a heavy ground clip. Never touch the ground wire while using the stick.
(Figure courtesy of ARRL.)
n FIGURE 1B. Voltage ratings are shown next to a voltmeter’s probe jacks
(1,000V DC and 750V AC). Exceeding these voltages can result in a flashover,
presenting a severe electrocution hazard.
Save the Screwdriver
Never (repeat after me ... never) use a screwdriver as a
grounding stick. They aren’t designed or intended for that use.
The handle may look like it has a lot of plastic, but you don’t
know if it’s a good insulator or not. There may be small internal
cracks that result in a lot less insulation than you think!
Screwdriver handles are often dirty or greasy which creates
a somewhat conductive path from the blade to your hand. Plus, if
you do happen to discharge a big capacitor, you’ll probably ruin
the blade with a big pit.
Take a few minutes and make yourself a good grounding
stick. Your screwdrivers will thank you for it!