Fisher Labs F 75 User Manual page 16

F75
Comprehensive Operating Manual & Guide to Metal Detecting
Ground Balancing (continued)
3. Turn the SETTINGS KNOB to adjust the setting.
The goal is to eliminate the sound as the coil is being pumped over the ground. In
some soils, the sound is not completely eliminated.
If the ground balance adjustment is incorrect, there will be a difference in the sound as the
searchcoil is either moving toward or away from the ground. It sounds like you are either
pulling the sound out of the ground, or pushing the sound into the ground.
• If the sound is louder as you raise the searchcoil, increase the ground balance setting.
• If the sound is louder as you lower the searchcoil, reduce the ground balance setting.
NOTE: Experienced users often prefer to adjust the ground balance to get a weak but audible
response when lowering the searchcoil. This is called adjusting for positive response.
Positive and Negative Response
The purpose of ground balancing is to adjust the metal detector to ignore ground minerals. If
the setting is incorrect, ground minerals will give either a positive or a negative response,
depending on which direction the adjustment is off.
POSITIVE RESPONSE
If the G.B. setting is too high a number, the response of minerals will be positive. This means
that when the searchcoil is lowered to the ground in PinPoint, Stat, or Motion All Metals mode,
the sound will get louder as the searchcoil approaches the ground. The sound will grow
quieter as the searchcoil is raised. What, if anything, you will hear in discrimination mode
depends on the discrimination setting.
When searching in an All Metals mode, if ground balance is properly set to cancel the ground,
and you sweep over a positive hot rock, the rock will give a "zip" sound similar to that of a
metal object.
NEGATIVE RESPONSE
If the G.B. setting is too low a number, the response of minerals will be negative. When the
searchcoil is lowered to the ground in PinPoint, Stat, or Motion All Metals mode, the machine
will be silent. The machine will sound off as the searchcoil is lifted away from the ground.
What, if anything, you hear in discrimination mode depends on the discrimination setting.
When searching in Motion All Metals mode, a negative hot rock will produce a "boing" sound
after passing over it, making it difficult to know where it is located. It will not have the sound
and "feel" of a metal object.
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