EPD/HB/40521/
000
ELECTRONIC PERSONAL DOSEMETER HANDBOOK
TECHNICAL DESCRIPTION
ISSUE 5
Page 58
Thermo
EPD ‘Run’ and Off times
The EPD contains an accurate clock (±30 ppm) and records the elapsed time,
both for operating (Run Time) and in ‘OFF’ Mode. Times are recorded to a
resolution of 1 second. The OFF time is the number of seconds that the detectors
have been switched off (while the power has been present).
Note
: When power is removed, or a reset occurs, the EPD clock reverts to a
value of up to 15 minutes prior to its value on power loss or reset.
EPD State
The EPD retains a record of the following information:
1.
Issue Count. This is the number of times the EPD has been issued.
2.
Issued
. This is the present state of the issued flag, either EPD
Issued or EPD Not Issued.
3.
Detectors State. This is the current state of the EPD’s operating mode,
i.e. ON or OFF.
Alarms
The EPD retains a record defining which of the following alarms has occurred.
The record is normally cleared by system software at the start of an issue period:
1.
3 Dose Alarm Flags
As section 4.6.8
2.
3 Dose Rate Alarm Flags
. As section 4.6.8
3.
Return For Read. The EPD clock has exceed the Return For
Read time.
Faults
The EPD retains a record of the following faults flags:
1.
Event Logged
. An event (possibly but not necessarily a fault)
has been logged in the EPD’s event store.
2.
Connection Failed. Communication with the EPD failed.
3.
Cal Factors Bad
. The EPD calibration factors failed a CRC
check and cannot be recovered from secure
store.
4.
EEPROM Fail. An un-recoverable EPD secure store failure
occurred.
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