19
2. THRESHOLD B
–
(THS-B) (BIAS)
Setting range 1-99
Factory preset at 50
YouTube Reference
to see how to set Threshold B.
Threshold B NULL Position
When looking for both rising and falling pitch targets it's best to put
THRESHOLD B in the NULL position (around 50) and raise
THRESHOLD A to create your desired threshold level.
Locating the “NULL Position” is determined by raising and lowering
Threshold B and taking note of the numbers as per the following
procedure:
•
Start by raising THRESHOLD B with the
button until the
THRESHOLD B starts to get to a tolerable volume level (e.g.
58).
•
Then lower THRESHOLD B with the
button until you get
the same volume level e.g. 44.
o
The above example range is 58 less 44 = 14.
o
Halve the 14, which becomes 7.
o
Add 7 to 44 = 51.
51 is then the THRESHOLD B NULL position in this example.
YouTube Reference
to see how to set Threshold B to NULL
Small Search Coils
When using small coils for small (tiny) targets, set the THS-B to an
acceptable audio level
below
the NULL position.
From the NULL position, decrease THRESHOLD B with the
button until an acceptable threshold volume is created (i.e. not too
noisy)
This will boost target responses for smaller targets in the ground.
Process:
•
If a small coil is fitted, test the THS-B out with a small target.
•
Swinging the coil over it will produce a
rising pitch response
.
•
Lower the THS-B by one count at a time and note the
improvement in detection distance.
•
Keep lowering THS-B until the background audio is at an
acceptable level.
Note: If THS-A is high then just a change of 1 or 2 on the BIAS will make the
QED too sensitive/unstable.
Tip:
Use a test target of say
0.2g. If the 0.2g is louder
and more noticeable
after lowering THS-B,
then BIAS has been
achieved for better
detection on smaller
targets
Tip:
When searching for
small targets: use a
small coil, a volume of
~30 or less, a gain of ~4,
with the THS-B set
below NULL until a
slight threshold is
created.
Summary of Contents for PL3
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