Fluke Biomedical 05-450 - Manual (Page 18)

05-450
Users Manual
10
Operator Controls and Setup
Calibration Controls
Remove the calibration cover to expose the calibration controls. The calibration
controls include the up/down buttons, five calibration potentiometers, and the
option dipswitch (detailed in the following subsection). The five potentiometers
are detailed below:
Warning
To prevent possible electrical shock, fire, or personal injury:
• To prevent contact with internal hazardous live parts that
are accessible using a tool: turn off the Product and
disconnect the power cord. Allow the Product to sit for
1 minute before accessing internal components.
• Do not touch the circuit board in the calibration window
due to potential for electric shock.
• ANALOG: Used to adjust the logarithmic analog voltage output. Adjusted in
calibration mode to the full-scale voltage reading or adjusted to a known point
at some given reading.
• HV: Used to set the high voltage required for detector operation. Adjustable
from 0 V dc to 2500 V dc. The high voltage required will depend on the type
of detector used. Internal GM detectors typically require 550 V dc. Be sure to
check the high voltage with a high impedance (1000-Mohm impedance)
voltmeter only. A high-voltage checkpoint is located next to the HV
potentiometer.
• DISC: Internal discriminator used to set negative pulse threshold for counting
pulses from the detector. Pad allows direct measurement of threshold
voltage. Utilize a Ludlum Model 500 Pulser or equivalent to inject pulses of
the desired threshold size. The pulse height threshold is adjustable from
2.0 mV dc to 100 mV dc.
• BAT CHARGE: Used to set the backup battery trickle charging voltage. It is
set to 6.9 V dc while the battery is disconnected.
• OVERLOAD: Used to set the detector current overload point. When
excessive radiation causes the detector to overload, this set point will cause
the FAIL light to engage, and the display will be forced to -OL-.