CREDO DDM Metal Detector, User Manual

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balancing. If there is no change in tone while doing this, then the sensitivity
may be increased further. For best results, the setting should be at the
maximum possible while maintaining a stable threshold tone. At maximum
sensitivity settings, a slight tone change may be noted when both raising
and lowering the coil. This will not adversely affect the operation of the
CREDO DDM, providing that the coil is kept at a reasonably constant level
above the ground surface and parallel to it while detecting.
Setting the desired Discrimination level is done by rotating the
Discrimination knob clockwise to INCREASE the discrimination level and
REDUCE the sensitivity to ferrous (iron); higher than necessary settings will
result in desired targets being missed. Rotating the
Discrimination knob
anticlockwise will DECREASE the discrimination level and INCREASE the
sensitivity to ferrous (iron) targets.
In general, an effective method of setting the Discrimination level, suitable
for most search conditions, is by passing a rusty iron nail (about 50mm
long) close to the search coil. Rotate the Discrimination knob clockwise
until the iron nail is rejected in every possible position against the coil. After
this procedure check if small non-ferrous targets are detectable without
loss of depth.
Finally, check again the threshold and volume settings for comfortable
levels.
The CREDO DDM
is now set up for the particular site conditions and is
ready for use.
Search Method
With the CREDO DDM
set up and ready, the coil should be swung
smoothly from side to side, a little above the ground surface. The sweep
speed should be according to the
Recovery settings. It is not effective to
‘scrub’ the coil on the surface of the ground (this can also damage the coil
and places strain on the stem assembly).
Suggested operating heights for the standard coils are:
13” DD coil:
2” (50 mm) minimum above ground surface
10” DD coil: 1½” (40 mm) minimum above ground surface
7”DD coil; Any distance.
Make sure that the coil is swung evenly over and parallel to the ground
surface and that the coil does not rise at each end of the swing. Cover the
ground in smooth, parallel swings to ensure maximum detection coverage.