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.
