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Using Your Tone Generator as a Retrofit Tool Using Your Tone Generator as a Retrofit Tool
TR January TIP-of-the-Month
Copyright 2007, Training Reels
This months TIP is all about
things you can do with a
standard tone-
generator/tone-detector to
help you locate a lot more
than cable in the wall! Find
plumbing, electrical wiring,
radiator pipes, drill bits, fish
tapes as well as the cable
youre trying to fish.
The right way to use the
tone generator
Almost all battery powered
tone generators work the
same way. They generate
an audio frequency A.C.
signal and apply it differentially to two wire leads, usually with alligator clips on
the end. The amplitude of the AC signal is usually large (10's of volts P-P)
compared to line level AC signals.
The two clips imply that you need to connect both leads for it to work properly,
but this is almost never the case. Most times you only need to connect one of
the leads (it doesn't matter which one) and in all our examples this is the way to
use it. Do not connect the other lead to anything. If you are trying to isolate a
single pair in a CAT5 TP cable for example, especially if the cable runs close to
other cables in the installation, you attach each tone generator lead to one of the
wires in the pair. This actually
reduces
the AC signal radiated by the cable,
making it easier to isolate the cable.
The right way to use the tone detector
Like the stud finder, using the tone detector requires some practice to learn what
it's telling you. Different manufacturers tone detectors will have different
sensitivities. When trying to isolate the source of the signal in a wall, slowly
move the detector left-right, then up-down for the strongest signal. If your
detector has a volume control, reduce the volume until you can just barely hear
the tone. This will help you isolate the source to a smaller area. Test to see
what effect the orientation of the detector has (horizontal, vertical, perpendicular
or parallel to the wall). Finding Cable
The most common use of the tone generator is to locate a cable you're fishing in
a wall cavity. This happens often, for example, when you've fished the cable
down from the attic and you can't find it in the wall cavity in the floor below.
You've been fishing around in the wall with a coat hanger for the past hour and
give up! Do you have the right cavity? Did the cable get hung up on insulation or
a nail or pipe? An easy way to find out is to have the guy in the attic attach the
tone generator to the end of the cable in the attic (or wherever it is) and you use
the tone detector to isolate the end of the cable in the wall. With a little practice,
you can get very good at this. Don't forget to reduce the detector volume as you
get close.
By the way, you don't actually need to connect the tone generator lead
directly to the copper in the cable. You can couple the tone to the
cable by wrapping a short wire (5 ft. or so) around the cable you want
to locate (for a few feetthe longer you wrap it, the stronger the
coupling) and attaching the tone generator to that cable. You should
experiment with this technique to see how well it works.
Finding drill bits
Another simple trick lets you locate the right wall cavity quickly. Lets say you've
drilled up into a wall cavity from the crawl space or basement below and want to
locate the right wall cavity in the floor above. After drilling through from below.
Have your buddy clip a tone generator lead directly to the drill bit and feed it up
the wall a few feet. Sweep the tone detector on the floor above across the wall
until you hear the exact location of the bit.
Finding wire bits
You drilled a small wire bit through the ceiling on the second floor into the attic (to
locate where to drill down from the attic) but you can't find the darn thing in the
two feet of loose insulation in the attic! Of course, attach the tone gen. to it and
sweep across the insulation in the attic with the tone detector.
Finding fish tape
This same technique works great to locate metal fish tapethe kind electricians
use to fish wire through conduit (and many of you are, unfortunately, still using as
your primary fishing tool). Just attach one lead of the tone generator directly to
the fish tape. You can locate it in the wall, under insulation, down an AC duct,
and so on.
Locating Plumbing
During your retrofit planning, you should try to get a good idea where the
plumbing runs are located, especially the cold/hot water supply lines. You can
"tone up" the metal plumbing lines in the house by simply attaching the tone generator lead directly to a water pipe, usually easily accessible under a sink.
Just clip it onto a valve handle. The closer you attach it to the wall you're
interested in, the better. Try a few different locations if necessary.
Locating electrical wiring
To locate existing electrical wiring in the wallthe one you're about to drill
sideways through a wall stud intoyou can attach the tone generator to the
neutral wire at a nearby outlet. This will "tone up" all the electrical wiring in the
home. The closer you are to where the tone generator is connected the louder
the tone signal. To make this easier and safer, purchase an A.C. plug at the
hardware store and remove the hot plug contact (the smaller contact) so you
don't accidentally us it. This will give you something easy to use to connect the
tone generator to the neutral wire. The ground wire will often work just as well
(theoretically is should work exactly the same, but it doesn't). Some tone
detectors will respond to the 60 cycle A.C. field around hot electrical wiring
(generating a hum) and some won't (purposely filtering it out). Even if yours will,
this is usually a very unreliable way to locate AC wiringthe field is too broad.
Experiment
I encourage you to experiment to find you own cool uses for your tone detector,
tone generator. The tone generator will work with anything metal. Please email
me (grayson@trainingdept.com) if you have good ideas I missed or questions or
comments on this TIP.
Catch you next month..Grayson