Fluke 05-443, Руководство пользователя

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05-443/05-444
Users Manual
16
Calibration
High Voltage
The high voltage is adjustable from 0 V dc to 2500 V dc using the HV
potentiometer located under the calibration cover. The high voltage required will
depend on the type of detector used. Internal G-M detectors usually require
550 V dc. Ensure that the high voltage is checked only with a high impedance
( ≥ 1000 megohm) voltmeter. A high-voltage checkpoint is located next to the HV
potentiometer.

Warning
To prevent possible electrical shock, fire, or personal injury, do
not touch the circuit board in the calibration window.
Calibration Parameters
The calibration parameters, LOW ALARM, HIGH ALARM, CAL CONST, and
DEAD TIME can only be changed while in calibration mode. Switch the top
dipswitch CAL MODE to the right to switch into calibration mode. Changing any
parameter is done by holding down the parameter key and pressing the up or
down arrow buttons. Any parameter can be set in the range of 0.1 to 9999. If a
parameter is changed, the instrument will beep to confirm the saving of the
parameter, and then return to displaying the current radiation level.
The calibration constant (CAL CONST) is set when the detector is exposed to a
"low" radiation field. A "low" radiation field in this case is defined as a field where
dead time losses do not exceed 5 %. The calibration constant is usually given for
a certain detector. Once the calibration constant is set and checked at a low
radiation field, the dead time correction can be set.
The dead time correction (DEAD TIME) is set when the detector is exposed to a
"high" radiation field. A "high" radiation field in this case is defined as a field
where dead time losses exceed 30 %. The dead time correction will elevate the
ratemeter reading to account for counts arriving at the detector during the
detector's dead time. G-M tubes typically have long dead times from
50 microseconds to150 microseconds.
Note
Once parameters are set, it is important to remember to switch the
CAL MODE switch back to the left. This action protects the
parameters from inadvertent changes.
Analog Output
The analog output is a five-decade logarithmic voltage-out. The maximum
voltage-out while under primary power is 6 volts. The maximum voltage out while
under battery backup power is 4.5 volts. The five decades are:
• 0.1 <units> to 1.0 <units>*
•
1 <units> to 10 <units>*
• 10 <units> to 100 <units>*
•
100 <units> to 1000 <units>*
• 1000 <units> to 10000 <units>*
When the CAL MODE dip switch is switched to the right, the analog output goes
to full scale. The analog output goes to full scale during a DET FAIL condition.