6
CALIBRATION
The DS71/DS72 Controller offers two modes of calibration or “teach”, a one-sample
mode and a two-sample mode. Both are invoked through the pushbutton on the face of
the unit.
The one-sample mode simply sets the gauge threshold at 125% of the signal present at
the time the pushbutton switch is pressed. The two-sample mode sets the gauge
threshold halfway between the readings from the two-sample calibrations.
Calibration information is stored in non-volatile memory and is restored at power-up.
One-sample Calibration
1. Place a single thickness of the metal to be sensed on the magnetic conveyor in
front of the probe face.
2. Press the calibration pushbutton once.
If successful the multi-function LED indicator turns off momentarily, and then flashes
amber 4 times in succession at a 5 Hz rate then turns solid green.
If calibration is not successful, the indicator flashes amber at a 10 Hz rate for 15
seconds or until the pushbutton is pressed again. The previous calibration values are
re-installed if 15 seconds elapses with no press of the pushbutton.
The detector has a standby calibration feature that permits calibration while the metal is
moving. Press the pushbutton once with no metal between the magnet field and probe.
The indicator will flash amber at a 2.5 Hz rate until metal is moves in front of the probe.
The controller will sense the effect the metal has on the magnetic field. It delays the
measurement for half (.5) second to allow full coverage of the metal over the
background magnetic field. If successful the indicator flashes green 4 times and
remains solid if metal remain present or off if no metal is present.
Two-sample calibration
Two-sample calibration may be used to tightly set the gauge tolerances. Two-sample
calibration places the gauge threshold at the midpoint between the two recorded
samples. Whereas the one-sample calibration always discriminates on a >25% change
in signal relative to the sample point. The separation of sample points in the two-
sample mode may be varied according to the user’s needs.
When calibrating in two-sample mode, the order of sampling the thicker and thinner
material makes no difference. The controller sorts out the order and sets the threshold
the same either way.
