Adjust SENSITIVITY
We are now ready to switch the detector into the discriminate mode
(DISC MODE). Go to the MODE switch and flip all the way to the right
and into the DISC MODE setting. The switch will lock into position and
you will notice that the threshold hum will stop. The discriminate circuit
uses a silent search mode, meaning that no sound will be heard until the
coil goes over a target. The most common use of the detector is to hunt in
the DISC MODE and switch to ALL METAL to pinpoint a target. This will
give you the advantage of ignoring unwanted targets and not having to
listen to the threshold hum until you are ready to pinpoint and dig a target.
The all metal circuit uses a single channel to detect various metals.
The discriminate circuit uses two different channels, then amplifies and
filters them. The detector will then compare the signals and determine
whether or not to beep at the target. While there is a great advantage to
ignoring unwanted targets, it can make the circuitry more susceptible to
interference. A number of outside conditions such as power lines, highly
mineralized soil, and wet salt sand can cause interference.
The SENSITIVITY knob is used to raise or lower the power to the
operational amplifiers, which changes the gain. Gain is a measurement of
how much a signal is amplified. The higher the gain the more depth and
sensitivity to small objects a detector has. Unfortunately, any small inter-
ference that is amplified can cause the detector to become erratic. The
SENSITIVITY control is used to find the best gain setting in any location
without letting the detector become unstable.