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Useful tips and tricks to find targets easier and
to keep
your locator healthy for a lifetime
It should be comforting to know that
your Dunham & Morrow Magnetic Locator uses the same technology used in
the magnetometers we designed and built for Hubble Space Telescope.
Those instruments have been working failure-free for more than a quarter
of a century and you can reasonably expect your Dunham & Morrow Magnetic
Locator to last just as long if you follow these few tips and
suggestions. You can also visit our
Troubleshooting page for solutions to
common problems. # 1 –
Working above asphalt, reinforced concrete & crushed blue stone
Searching for a target buried under asphalt, reinforced concrete or
crushed blue stone? Try this. Raise the locator tip
eight inches to one foot above the ground.
The magnetic field
of small surface targets or buried rebar drops off faster than the
magnetic field of a survey pin, or a manhole cover, thus making these
targets easier to detect.
Blue stone is magnetic but the dipoles are
short and the magnetic field drops off fast. A magnetic Survey Pin,
on the other hand, is typically 18” long and the magnetic field of
its dipole drops off
 much slower. Consequently, when you lift up on
the locator the magnetic field of the shallow, surface material
disappears leaving only the magnetic field of your buried survey
pin. This principle works well whenever there is extensive surface
interference and you suspect your target lies buried beneath.
# 2 – Working near cyclone or chain
link fences
If you're searching
for a target near a cyclone fence, step away from the fence. Walking parallel to the fence with the locator about
a foot away, you'll find that the magnetic field of the fence drops
away fast while the magnetic field of a survey pin remains strong.
You'll hear the field of the fence and the fence posts increase
and decrease as you walk along, but the signal of the survey pin will
be much stronger and unique. You'll have no difficulty
distinguishing your survey pin from the cyclone fence.
# 3 – When
the instrument audio output warbles
WARNING!
DO NOT DIG IN THIS AREA
The WARBLE is an indication of nearby energized power lines
Pay attention to a warbling output.
The warble is produced by the 60 hertz power line frequency modulating
the normal audio output tone of the instrument. If the
warble output signal is strong you are probably directly over a buried
power line.
If the output warble signal is weak,
most likely you are over a copper water pipe or buried communications
cable.
# 4 - Batteries
The number one problem with all locators are the BATTERIES. Two
thirds of all repairs are the result of battery related problems.
It’s easy to forget that batteries
contain acid, and when they get old and weak, they leak. When batteries leak the acid corrodes
causes havoc. Once the the battery terminals are damaged, the unit
stops working. If the batteries remain in the unit, all too frequently
the battery acid drips on to the locator’s main printed circuit board
multiplying the problems and the cost of repair.
To Avoid problems, remove and
replace the batteries every six months even if the low battery indicator
light isn't flashing. If you're storing the unit for any length of time,
remove the batteries and install new, fresh batteries when work resumes.
For the best protection, keep your electronics DRY at all times.
# 5 - Mishandling
Even as rugged as Dunham & Morrow units are they'll eventually succumb
to intentional abuse. The sudden impact of being dropped or
carelessly thrown into the back of the truck causes the wiring harness
inside the sensor tube to flex. In most cases, it takes several years
and hundreds of drops, but the damage is cumulative and eventually one
of the wires will break.
To Avoid problems don’t drop or
throw the unit. When you are through for the day put it back into its
carrying case and lay it in the back of the truck.
# 6 – Your locator is not a shovel
Occasionally we have locators returned with broken cases. In some
instances, the operator simply ran over the unit with the truck. In
other cases, though, the operator used the locator to expose his target
and, rather than holding the unit by the aluminum sensor tube, he tried
increasing his leverage by grasping the instruments’ case.
This is an invitation to disaster
and in every instance the problem is still - operator error.
The natural tendency is to confirm the
accuracy of your search by exposing the target. There you stand, locator
in your hand, a strong audio output signal ringing in your ear and a
narrow ended "tool" just inviting you to dig. Don’t do it! The
consequences could easily be a broken locator with an expensive repair
bill. You can also visit our
Troubleshooting page for solutions to
common problems.
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