Fluke Biomedical 945A - Manual (Page 29)

Operational Modes
Rate Mode (Normal Operation)
The system is in RATE MODE when SW3-3 on the high voltage /comm board (Model 977-210-10) in the
preamplifier is set to the OFF position, the UDR function switch is in any position, but 8 or 9, and the
Check Source button is OFF. In the Rate Mode, the display shows the dose rate data received from the
preamplifier in mR/h, R/h, or kR/h units as appropriate. The bargraph also shows the dose rate. The
color of the illuminated segments is green when the dose rate is below the WARN setpoint, amber when
the dose rate is above the WARN setpoint and below the HIGH setpoint, and red when the dose rate is
above the HIGH setpoint. The analog outputs are active while the UDR is in RATE MODE and all alarms
are enabled.
Data Entry Mode
Data Entry Mode is selected by pressing the ENTER push-button while the rotary FUNCTION switch is in
a valid setpoint position (see How to Enter Setpoints). The selected setpoint is displayed in exponential
format (e.g. 1.00E2) with the left most digit flashing. If the FUNCTION switch is not in a setpoint position,
pressing the ENTER button has no effect. Refer to Table 4-2 for FUNCTION switch positions.
In the Data Entry Mode, the alarms, bargraph and analog outputs are active. The check source and
alarm acknowledge functions are inoperative.
Alarm Inhibit Mode
Alarms are inhibited in situations where an alarm trip would be meaningless, because the UDR
preamplifier is not in a normal measurement mode (i.e., when the UDR is in the Check Source Mode).
New alarm trips cannot occur and old alarms cannot be reset. When the inhibit period is over, alarm trips
and resets are enabled again. Alarm inhibit conditions are discussed in the following paragraphs. Alarms
are inhibited for three minutes after channel power-up to allow time for induced charges within the
detector output to subside.
Check Source Mode
In the Check Source Mode, the dose reading displayed is the result of pulsing the high voltage to the
detector to simulate a radiation field. The value displayed is in the nominal range of 2.5 to 5 R/h and is
dependent on component value and gain in the check source driver. When in the check source mode,
alarms may be inhibited or active depending on jumper selection (JP3-5). Analog outputs are always set
to zero during check source operation.
To operate the check source, press the CHECK SOURCE push-button and hold it down for
approximately 1 second. The electronic check source circuit will energize, the green check source
indicator will illuminate (approximately 1 second after the button is depressed), and the check source
radiation value will be displayed on the front panel. An internal configuration jumper allows alarms to be
activated or muted if alarm limits are exceeded by the check source radiation value. The alarm inhibit
function may be disabled by removing jumper JP3-5 from the UDR main board. If this is done, alarms will
be enabled in Check Source Mode.
Pressing the CHECK SOURCE push-button again will cause the UDR to return to normal operation.
A built-in timer will turn the Check Source OFF after 10 minutes.
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