GROUND BALANCING (continued)
MANUAL GROUND BALANCING (continued)
The Fe
3
O
4
bar graph on the LCD display indicates the amount of magnetic mineralization.
The searchcoil must be in motion to measure Fe
3
O
4
. The most accurate measurement is
obtained by pumping the searchcoil, as in the Ground Balancing procedure.
The two-digit G.B. Setting number displayed on the LCD indicates the type of ground
mineralization.
Some typical ground mineralization types are:
0 – 10 Wet salt and alkali
5 – 25 Metallic iron. Very few soils in this range. You are probably over metal.
26–39 Very few soils in this range -- occasionally some saltwater beaches
40–75 Red, yellow, and brown iron-bearing clay minerals
75–95 Magnetite and other black iron minerals
When manually ground balancing, try to “feel out” a spot on the ground to make sure
there is no metal present. In order to avoid locking onto metal, the computer will not
balance to ground where the GB setting is less than 40. Where the ground reads less than
40, manual ground balancing is required.
To perform the Manual Ground Balancing operation, do the following:
1. Select the MANUAL G.B. function
The legend G.B. SETTING appears.
The present ground balance setting is displayed (0-99).
The message PUMP COIL TO G.B. will appear.
2. Physically pump the searchcoil and detector up and down over the ground.
Lift it about 6 inches above the ground and lower it to within 1 inch
of the ground, about once or twice a second.
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.
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