EPD/HB/40521/000
ELECTRONIC PERSONAL
DOSEMETER
(EPD Mk2)
TECHNICAL HANDBOOK
DATE OF ISSUE: APRIL 2004 CHANGE REFERENCE: Thermo Electron Corp. Revision
© Thermo Electron Corporation. All rights reserved.
The information contained herein is the property of Thermo Electron Corporation and is supplied
without liability for errors or omissions. No part may be reproduced or used except as authorised
by contract or other written permission. The copyright and the forgoing restriction on reproduction
or use extend to all the media in which this information may be embodied.
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MANUFACTURERS DETAILS
Manufacturer's Address
Thermo Electron Corporation
Sopers Lane
Poole
Dorset
United Kingdom
BH17 7ER
Tel. (01202) 782779 International: + 44 1202 782779
(01202) 782374 International: + 44 1202 782374
(01202) 782780 International: + 44 1202 782780
Fax. (01202) 782335 International: + 44 1202 782335
USA Sales Office
Thermo Electron Corporation
105C Hembree Park Drive
Roswell
GA 30076
U.S.A.
Tel. 770 521 4502
Fax. 770 521 4535
Pages Issue Type Part ID File ID
All 5 ESERS EPD/HB/40521 HB40521_iss_5.doc
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CONTENTS
GLOSSARY................................................................................................................................................................IX
CAUTIONS.................................................................................................................................................................XI
SECTION 1...................................................................................................................................................................1
INTRODUCTION........................................................................................................................................................1
1.1 GENERAL ..................................................................................................................................................1
1.2 EPD MAJOR CHARACTERISTICS.........................................................................................................1
1.3 BRIEF FUNCTIONAL DESCRIPTION........................................................................................................2
SECTION 2...................................................................................................................................................................5
GETTING STARTED..................................................................................................................................................5
2.1 SETTING-UP..............................................................................................................................................5
2.1.1 Unpacking The EPD......................................................................................................................6
2.1.2 The EPD Battery .............................................................................................................................6
2.1.3 Start-up Sequence................................ ..........................................................................................9
2.1.4 EPD Confidence Test..................................................................................................................10
2.1.5 Issuing an EPD..............................................................................................................................10
2.1.6 Wearing an EPD............................................................................................................................11
OPERATING INSTRUCTIONS ..............................................................................................................................13
Page
3.1 LCD DISPLAY AND BACKLIGHT .........................................................................................................13
3.2 AUDIBLE AND VISIBLE ALARMS.........................................................................................................16
3.2.1 Alarm features ................................................................................................................................16
3.2.2 Dose Alarms...................................................................................................................................20
3.2.3 Dose Rate Alarms.........................................................................................................................20
3.2.4 Over-Range Indication .................................................................................................................21
3.2.5 Alarm Muting...................................................................................................................................22
3.3 BUTTON OPERATION AND DISPLAY SELECTION..............................................................................23
3.4 LCD DISPLAY LOCK-ON FACILITY.................................................................................................... 24
3.5 DISPLAY OPTIONS AND BUTTON FUNCTIONS..................................................................................26
3.5.1 Displaying Hp (10) Dose, Dose Rate and User ID..............................................................26
3.5.2 Displaying Hp(0.07) Doses, Dose Rate and ADS User ID ...............................................27
3.5.3 Displaying Total Dose..................................................................................................................29
3.5.4 Starting/Stopping The Seconds Count Down Timer...........................................................29
3.5.5 Turning the EPD off ......................................................................................................................30
3.5.6 Displaying Peaks (Rate High)...................................................................................................31
3.5.7 EPD Confidence Test..................................................................................................................32
3.5.8 Clearing Dose Displays ...............................................................................................................34
3.5.9 Displaying/Setting Dose Alarm Thresholds...........................................................................34
3.5.10 Displaying/Setting Dose Rate Alarm On/Off Thresholds................................ .............36
3.5.11 Setting The Sounder ...............................................................................................................38
SECTION 4.................................................................................................................................................................43
TECHNICAL DESCRIPTION.................................................................................................................................43
4.1 GENERAL ................................................................................................................................................43
4.2.1 Electrical Characteristics............................................................................................................44
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4.2.2 Battery Management....................................................................................................................44
4.3 MECHANICAL DESCRIPTION ................................................................................................................46
4.3.1 Mechanical Characteristics And Dimensions .......................................................................46
4.3.2 Brief Mechanical Description.....................................................................................................46
4.4 ENVIRONMENTAL DESCRIPTION .........................................................................................................48
4.4.1 Environmental Characteristics ..................................................................................................48
4.4.2 Brief Environmental Description ...............................................................................................48
4.5 INFRA-RED INTERFACE.......................................................................................................................... 49
4.5.1 Communicating With The EPD.................................................................................................49
4.6 EPD INTERNAL PROCESSING & FACILITIES..................................................................................... 51
4.6.1 Memory Characteristics: .............................................................................................................51
4.6.2 Alarm Characteristics:.................................................................................................................52
4.6.3 Default Display...............................................................................................................................52
4.6.4 User Identification.........................................................................................................................52
4.6.5 Dose and Dose Rate ....................................................................................................................53
Dose..................................................................................................................................................................53
Dose Rate................................ ........................................................................................................................53
4.6.6 Counts..............................................................................................................................................54
4.6.7 Dose Quality Flags.......................................................................................................................55
(i) Reset Count..............................................................................................................................................55
(ii) Shock Time Seconds...........................................................................................................................55
(iii) Dose Over -range...................................................................................................................................55
(iv) Dose Rate Over -range.........................................................................................................................55
(v) Counter Over -range ...............................................................................................................................55
(vi) Abuse Warning ......................................................................................................................................56
(vii) CRC Failure ...........................................................................................................................................56
4.6.8 Dose And Dose Rate Alarm Processing................................................................................56
4.6.9 EPD Operating Status .................................................................................................................57
EPD ‘Run’ and Off times................................ .............................................................................................57
EPD State.......................................................................................................................................................57
Alarms ..............................................................................................................................................................58
Faults................................................................................................................................................................58
4.6.10 Dose Profile ...............................................................................................................................59
4.6.11 Event History Store.................................................................................................................59
SECTION 5.................................................................................................................................................................61
EPD FAULTS AND RECOVERY ACTIONS........................................................................................................61
5.1 OVERVIEW ..............................................................................................................................................61
5.2 VISUAL AND AUDIBLE FAULT INDICATION................................................................................... 62
5.3 INTERNAL LOGGING OF FAULT CONDITIONS .................................................................................... 63
5.3.1 EPD Status Faults Record.........................................................................................................63
5.3.2 Event History store .......................................................................................................................63
5.4 BLANK LCD DISPLAY AND OTHER FAULTS..................................................................................... 65
5.5 INITIALISATION E RROR ( LCD ---- )...................................................................................................67
5.6 COMMUNICATIONS ERROR ( LCD ==== ).......................................................................................67
5.7 LCD DISPLAY ERROR CODES.............................................................................................................69
5.8 RECOVERY PROCEDURES .....................................................................................................................70
5.8.1 Logging Faults / Extracting Data ..............................................................................................70
5.8.2 Clearing faults ................................................................................................................................70
SECTION 6.................................................................................................................................................................77
MAINTENANCE........................................................................................................................................................77
6.1 CALIBRATION......................................................................................................................................... 77
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6.2 THE EPD BATTERY............................................................................................................................... 79
6.2.1 Replacement Batteries ................................................................................................................79
6.2.2 Battery Leakage............................................................................................................................79
6.2.3 Lithium Thionyl Chloride Battery Warning..............................................................................80
6.2.4 Replacing the EPD Battery ........................................................................................................81
6.3 EPD CLIP ASSEMBLY.......................................................................................................................... 82
6.3.1 Removing the EPD Lanyard Plate/Clip Assembly..............................................................83
6.3.2 Replacing The EPD Lanyard Plate/Clip Assembly................................ .............................84
6.4 CLEANING............................................................................................................................................... 85
6.4.1 General Cleaning...........................................................................................................................85
6.4.2 Radiological Cleaning................................ ...................................................................................85
6.4.3 Cleaning after a Battery Leakage.............................................................................................85
6.4.4 Periodic Cleaning ..........................................................................................................................86
APPENDIX A..............................................................................................................................................................87
RADIOLOGICAL SPECIFICATIONS..................................................................................................................87
APPENDIX B..............................................................................................................................................................89
ELECTROMAGNETIC COMPATIBILITY...........................................................................................................89
APPENDIX C..............................................................................................................................................................95
SUMMARY OF GENERAL PHYSICAL & FUNCTIONAL CHARACTERISTICS ....................................95
APPENDIX D..............................................................................................................................................................99
EPD FAULT LOG FORM.........................................................................................................................................99
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GLOSSARY
/h Per hour
°C Degrees Celsius
ADS Approved Dosimetry Service (or System)
CRC Cyclic Redundancy Check. Error checking code.
dB(A) Decibels - ‘A’ weighted scale (sound intensity)
DC Direct Current
DDE Deep Dose Equivalent (alternative nomenclature for Hp(10))
Dose The accumulated dose to which alarm thresholds apply, intended for
tactical dose monitoring (eg. per day, per week, per shift etc)
Double-press Pressing the button twice in quick succession
EEPROM Electrically Erasable Programmable Read Only Memory
EPD Electronic Personal Dosemeter
EPDS Electronic Personal Dosimetry System
eV Electron Volt
Gy Gray, SI unit of dose
HEX Hexadecimal
H10 EPD LCD nomenclature for personal dose (Hp(10))
H07 EPD LCD nomenclature for personal dose (Hp(0.07))
H10/h EPD LCD nomenclature for dose rate (Hp(0.07)/h)
H07/h EPD LCD nomenclature for dose rate (Hp(10)/h)
Hp(10) Personal dose equivalent at a depth of 10mm of tissue (‘penetrating’,
‘deep’ or ‘whole body’ dose).
Hp(0.07) Personal dose equivalent at a depth of 0.07 mm of tissue (‘superficial’,
‘shallow’ or ‘skin’ dose).
Hp(10)/h Hp(10) dose rate
(0.07)/h Hp(0.07) dose rate
Hp
ICRU International Commission on Radiation Units
ID Identification
IR Infra-red
IrDA Infra-red Data Association
keV Kilo Electron Volt
LCD Liquid Crystal Display
LED Light Emitting Diode
Long Press Pressing and holding the button
LTC Lithium Thionyl Chloride (Sulphurous Oxychloride, SOCl2)
MeV Mega Electron Volt
m metre/milli
mm millimetre
nm nanometre
NRPB National Radiological Protection Board - the statutory authority for
radiological protection in the UK
PCB Printed Circuit Board
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Glossary (continued)
SDE Shallow Dose Equivalent (alternative nomenclature for Hp(0.07))
ppm Parts per million
RAM Random Access Memory
rem A unit of dose equivalent, equal to 10mSv
RFI Radio Frequency Interference
Short-press A short press and release of the button
Sv Sievert, SI unit of dose equivalent
T Tesla
TLD Thermoluminescent Dosemeter
Total Dose Intended to be a secure record of the total accumulated dose received
since Dosemeter issue - alarms do not apply to total dose.
User ID A numeric code of up to 12 digits that may be written to the EPD to
define the current user or wearer. By convention a value of
FFFFFFFFFFFF is written to EPDs not currently issued to a wearer.
User Name A character string of up to 22 characters that may be written to the EPD
and used as a second or supplementary Wearer Identity
( Supplementary to user ID ).
Wearer ID Alternative terminology for the User ID.
Wearer Name Alternative terminology for the User Name.
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WARNINGS
Radioactive Contamination
DURING OPERATIONAL USE THE EPD MAY BECOME EXPOSED TO RADIOACTIVE
CONTAMINATION. THE EPD MUST BE SUBJECT TO ALL RELEVANT
DECONTAMINATION PROCEDURES LAID DOWN BY THE RADIOLOGICAL PROTECTION
AUTHORITY.
Lithium Thionyl Chloride Batteries
LITHIUM THIONYL CHLORIDE* (LTC) BATTERIES ARE POTENTIALLY DANGEROUS.
THEY MAY LEAK TOXIC SUBSTANCES THAT CAN BE HARMFUL. READ AND TAKE
NOTE OF THE MANUFACTURERS WARNINGS ON THE BATTERY CASE . READ ALSO
THE DETAILED LTC BATTERY WARNINGS IN THIS HANDBOOK.
* Sulphurous Oxychloride, SOCL2
Cautions
EPD batteries
Batteries are susceptible to fire and abuse. Some manufacturers provide batteries with a
safety vent, which allows a controlled release of electrolyte if fire and abuse conditions prevail.
If the EPD has been damaged in a manner that could affect the battery, care must be exercised
during battery removal. The battery may have vented into the EPD case and caused the EPD
to become pressurised.
Take care when removing the EPD battery cap, the battery cap may spring free with
unexpected force.
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SECTION 1
INTRODUCTION
This handbook is for the Thermo Electron Electronic Personal Dosemeter (EPD) EPD Mk2. The EPD Mk2 is lighter and slimmer than the original Thermo Electron
EPD and has new micro-circuitry, case design and software. The EPD Mk2 also has
a number of enhanced dosimetry features and user functions. To simplify
nomenclature the term EPD has been used throughout this handbook. The term EPD
should be read to signify the EPD Mk2.
1.1 General
The EPD is a personal radiation monitor that detects and measures beta and gamma
radiation. Radiation that is detected by the EPD is processed to give an indication of
penetrating dose, superficial dose and the dose rates. This information is displayed
to the user via an LCD display on the top of the EPD.
The EPD contains three silicon diode detectors. Each detector feeds a chain of
dedicated amplifiers and counter circuits to measure soft gamma, hard gamma and
beta rad iation. The outputs from each detector chain are processed to calculate and
display penetrating and superficial dose and dose rate. Other functions include:
EEPROM storage of detected radiation, annunciation of alarm conditions (LED and
sounder), Infra-red (IR) communication and a user interface comprising an LCD
display and button. Each of the above functions is described in detail in this
handbook.
1.2 EPD Major Characteristics
Major Characteristics relating to the EPD are listed in Table 1.1.
Item Characteristic
Power One AA battery, either a standard Alkaline (1.5 V) battery or
Weight 95 gms (including LTC battery and clip).
Dimensions 86 x 62 x 18.5 mm (excluding clip).
Alarm sounder 98 - 101 dB.
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Table 1.1 - EPD Major Characteristics
high energy Lithium Thionyl Chloride (LTC) (3.6 V).
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The new EPD also has the following major features:
♦ Improved immunity to radio frequency interference (RFI).
♦ Display Backlight.
♦ EPD communication via an infra-red interface up to a range of approximately
1 metre.
♦ Improved dose profile facility.
♦ Real-time dose chirp (adjustable).
♦ Password protected dose store for ADS functions.
♦ Extended systems integration facilities.
♦ Count down timer and alarm.
Appendix C is a summary of the general physical & functional characteristics of the EPD.
1.3 Brief Functional Description
The EPD is a highly sophisticated device sensitive to gamma and X -rays (photons),
and beta radiation (energetic electrons) in the following energy range:
gamma, X-rays : 15 keV to 10 MeV
Beta radiation: 250 keV to 1.5 MeV (mean energy)
A full list of radiological characteristics and specifications can be found in Appendix A
to this Handbook.
Radiation detected by the three silicon diode detectors is combined to give the
following dose equivalents (as defined by ICRU Document 47):
(i) Hp(10) personal dose equivalent at a depth of 10mm of tissue (‘penetrating’,
‘deep’ or ‘whole body’ dose).
(ii) Hp(0.07) personal dose equivalent at a depth of 0.07 mm of tissue
(‘superficial’, ‘shallow’ or ‘skin’ dose).
The EPD calculates both the accumulated dose and the dose rate for Hp(10) and
Hp(0.07). These, and other data, are stored in an internal store (EEPROM) within the
EPD. A button in the EPD case allows the user to retrieve this data from store, select
a range of displays, acknowledge alarms and perform user control functions. Data is
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displayed to the user on a LCD display on the top of the EPD (see Figure 2.1). To
minimise the loss of data from battery or other failure, data is saved to secure
memory within the EPD every 15 minutes.
Data is written to and read from the EPD via an integral infra-red communications
interface. The Thermo Electron supplied EasyEPD2 program reads and writes data
to the EPD via the Infra-red communications link and displays the data in a PC
window. Thermo Electron also produces a range of Access Control Systems for use
with the EPD.
Dose is accumulated separately in the EPD in three stores: Dose, Total Dose and
ADS Dose . The use of several stores allows dose to be recorded over differing
periods, for example the Dose store may be used for each job or task performed (
and reset after each ), whilst the Total Dose records the total or aggregate dose from
all the jobs or tasks performed. ADS Dose is a password -protected dose store
intended for ‘legal dosimetry’ applications. Note that audible alarms are given if either
the accumulated dose or dose rates exceed programmable threshold levels. Dose
alarms are raised against the Dose store only.
The EPD is a sealed unit and is splash-proof. The unit will withstand short periods of
immersion in water but is not designed for prolonged immersion under pressure.
General maintenance is confined to:
♦ Removing/replacing the EPD battery,
♦ Removing/replacing the EPD clip assembly,
♦ Clearing fault conditions (where possible),
♦ Checking the functionality and calibration of the EPD,
♦ Keeping the unit clean.
Note:
1. This manual deals with Sieverts (Sv) throughout. To convert to rem multiply all
values by 100.
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SECTION 2
GETTING STARTED
This section describes the general procedures that must be carried out to ensure that
the EPD is set-up correctly and is functionally operational.
2.1 Setting-up
The EPD requires very little setting-up. Setting-up is primarily confined to:
1. Unpacking the EPD,
2. Inserting the battery,
3. Checking the initialisation sequence,
4. Checking the default settings,
5. Performing a confidence test.
A general view of the EPD is shown in Figure 2.1. External features are described in
Table 2.1.
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Figure 2.1 - External View Of The EPD
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Feature Description
Battery Compartment Houses an Alkaline AA battery (1.5 V) or a Lithium
Thionyl Chloride (LTC) AA battery (3.6 V).
Infra-red Interface Infra-red communications interface to the EPD.
Button User interface for EPD control, alarm acknowledgement
and LCD display selection.
Soun der Provides an audible indication of an EPD alarm.
Beta Window Allows beta particles to pass through the case to the
Beta detector.
LCD Display Displays EPD parameters and/or functionality as
selected by the button.
Alarm LED Provides a visual indication of an EPD alarm.
Clip Assembly Provides a means of attaching the EPD to clothing, or
for attaching a lanyard as an alternative means of
wearing the EPD.
Table 2.1 - EPD External Features
2.1.1 Unpacking The EPD
There are no special unpacking instructions. Depending on customer requirements
the EPD may, or may not, be shipped with a battery and/or a clip assembly.
Alternatively, the EPD may be shipped with just a lanyard plate and lanyard (see
Section 6.3). The battery, if supplied, may be a LTC or Alkaline type.
2.1.2 The EPD Battery
LITHIUM THIONYL CHLORIDE* (LTC) BATTERIES ARE POTENTIALLY
DANGEROUS. THEY MAY LEAK TOXIC SUBSTANCES THAT CAN BE
HARMFUL. READ AND TAKE NOTE OF THE MANUFACTURER’S WARNINGS
ON THE BATTERY CASE. READ ALSO THE DETAILED LTC BATTERY
WARNINGS ON PAGE 6.2 OF THIS HANDBOOK.
WARNING
* Sulphurous Oxychloride, SOCl2)
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General Precautions and Instructions
Always fit new undamaged batteries of the correct type (see section 6.2). A time
interval of at least 10 seconds must elapse between removal and replacement of the
EPD battery (this allows the internal circuits of the EPD to power-down).
The EPD is fitted with either a security-type (tamper-proof) battery cap or a coinrelease battery cap, depending on customer requirements (see Figure 2.2). The
security -type battery cap restricts unauthorised removal of the cap and requires a
special tool. The coin type battery cap should be rotated using a small coin circa 20
mm diameter and 2 mm thick.
Figure 2.2 - Battery Cap Types and Special Tool
The battery cap also provides the return path for the EPD’s power supply.
Therefore, during fitment of either type of battery cap the EPD will begin its start-up
sequence (see Section 2.1.3). If the battery cap is not fitted cleanly and contact is
temporarily broken, the software initialisation process may not be successful. Under
these circumstances it is essential that the battery cap is removed and that a time
interval of at least 10 seconds elapses before any attempt is made to refit the battery
cap.
Inserting/Replacing The EPD Battery
Caution:
Take care when removing the EPD battery cap, the cap may spring free with
unexpected force.
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To set up the EPD for operational use the battery must be inserted/replaced in
accordance with the following procedure:
(i) Read and observe the General Precautions and Instructions at the beginning
of this section. If necessary remove the battery cap from the case as
described in (ii) and (iii) below.
(ii) If the battery cap is of the security type, locate the two pips of the special tool
into the two conical recesses in the battery cap. If the battery cap is of the
coin type, locate the coin in the groove in the battery cap.
(iii) Maintain steady pressure on the special tool or coin so as to keep it fully
engaged in the battery cap and rotate the battery cap through approximately
85° in a counter-clockwise direction (to remove cap, see Figure 2.3). If a
battery is already fitted, the cap will normally release from the case under the
action of the battery cap compression spring.
Note: Do not attempt to rotate the cap beyond the design point
(approximately 85 degrees) or beyond the point where the
resistance of the end-stop is felt.
(iv) Remove the existing battery (if fitted). Insert a new (or replacement) battery
into the battery compartment as shown in Figure 2.4.
Note: The battery must be inserted anode (+) first.
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Figure 2.3 - Battery Cap Removal
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Figure 2.4 - Inserting The EPD Battery
(v) To fit the battery cap, first locate it against the special tool or coin, as
appropriate) and align the battery cap tangs with the recesses in the EPD
body. Push the battery cap into the battery compartment opening, ensuring
that:
a) the body of the battery cap, which houses the (-) electrode contact
plate, is fully engaged within the battery compartment,
b) the cap sits flush with the body of the EPD.
(vi) Using the special tool or coin, as required, maintain pressure on the battery
cap (against its compression spring), and rotate the battery cap in a clockwise
direction, through approximately 85°, to its end-stop. Rotate the cap slowly to
the point where the resistance of the end stop is felt. Avoid use of excessive
force.
2.1.3 Start-up Sequence
When a battery is inserted into the EPD, fitment of the battery cap will automatically
initiate the start-up sequence. The start-up sequence is as follows:
1. ‘8888’ is shown on the display for approximately three seconds;
2. internal software initialisation, which checks the state of the EPD (such as
the internal bus, internal memory, each detector amplifier and counter
chain, etc.);
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3. confidence test sequence, see section 2.1.4 below.
If the confidence tests pass, the EPD default display will appear. The EPD default
display is preset at the factory to show Hp(10) (the penetrating or deep dose) or to
another default display as specified by the customer.
If a fault code is displayed, or the start-up sequence repeats, try a fresh battery. If
problems persist, refer to section 5.
2.1.4 EPD Confidence Test
The EPD has an built-in confidence test facility. This runs automatically at startup
following battery change. When enabled, this test can als o be run at any time during
operational use as a check that the EPD is functioning correctly. The confidence test
is selected by scrolling through the EPD LCD displays to the CONFIDENCE TEST
menu (see Section 3.5.7). Throughout the confidence test the heart-beat (activity)
indicator flashes once per second. The confidence test can be stopped at any time
by pressing the button.
The confidence test sequence is as follows. This test sequence is automatic and
should be visually confirmed as each step initiated:
1. All segments of the display are activated for approximately 5 seconds. This
allows the user to check that all segments are functional (see Figure 3.2).
2. The alarm will sound and the LED will flash for approximately 2 seconds. This
indicates that the sounder and LED are functional.
3. The all-segment display will disappear. The alarm will continue to sound and
the LED will continue to flash, at an increased rate, for approximately 6
seconds. This indicates that all LCD segments can be turned off, and that the
tone frequencies are functional.
4. The all-segment display will reappear for approximately 5 seconds and the
LED will slow flash.
5. The all-segment display will disappear and the default display will appear. This
indicates that the confidence test has been successfully completed and that
the EPD is ready for operational use.
2.1.5 Issuing an EPD
In order to issue an EPD (i.e. assign it to a person) the EPD should be configured
with a numerical User ID and optionally with a User Name. There is a similar, but
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separate, configuration for Approved Dosimetry Service (ADS). The User Name and
numerical ID can only be configured via the IR communications link.
Controlled and ADS User IDs can be viewed via the EPD’s LCD display. Detailed
instructions to display User IDs are given in Section 3.5.
2.1.6 Wearing an EPD
The EPD should be worn under the direction of the health physicist. For most
operating conditions it is recommended that the EPD be worn on the outside of any
protective clothing (see Figure 2.5). Note that the button should be facing outwards.
Wearing the EPD on the outside of protective clothing has the major advantage that
the user can read the EPD’s LCD display and operate the button as required.
Typically, the EPD should be worn on the chest or the waist. The type of outer
protective clothing will determine how the EPD is attached (i.e. the EPD clip or
lanyard). For example, if the protective clothing has no breast pocket (or the use of a
belt is prohibited) the lanyard may be the most practical method of wearing the EPD.
Note: The lanyard cannot be fitted without first removing the lanyard plate (see
Section 6.3.1).
When the EPD is worn on the outside of protective clothing, to minimise the risk of
contamination of the EPD, consideration should be given to wearing the EPD in a
suitably -sealed plastic bag.
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Figure 2.5 - Wearing An EPD
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WARNING
DURING OPERATIONAL USE THE EPD MAY BECOME EXPOSED TO
RADIOACTIVE CONTAMINATION. THE EPD MUST BE SUBJECT TO ALL
RELEVANT DECONTAMINATION PROCEDURES LAID DOWN BY THE
RADIOLOGICAL PROTECT ION AUTHORITY.
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SECTION 3
OPERATING INSTRUCTIONS
This section explains the essential functions performed by the EPD and describes
operating instructions that will allow the user to display data, acknowledge alarms
and operate the EPD.
3.1 LCD Display and Backlight
A custom-designed LCD display on the top of the EPD provides a visual interface for
viewing dose and other EPD data. The EPD display is illustrated in Figure 3.2, which
shows all segments in the on state. All segments are activated in this way
temporarily during the start-up sequence, and during user initiated Confidence Test,
(see Section 3.5.7). On completion of the start-up sequence or Confidence Test the
default display will appear.
The default display is preset at the factory to show Hp(10) (the penetrating or deep
dose), or another default display as specified by the customer. The default display
can also be changed by the customer after delivery, to any display shown in Figure
3.4. Default settings and other display controls are changed using a suitable IR
communications link and software (e.g. EasyEPD2). For example, the display can
be configured to display values in either Sieverts or rems.
The EPD is provided with many different displays in order to provide a powerful
‘stand-alone’ facility for users not having direct access to communications software
such as EasyEPD2. However for many users the sheer number of displays
available may lead to confusion and Thermo Electron has therefore provided a
facility for unwanted or unnecessary displays to be disabled.
Backlight Operation
The EPD is equipped with a display backlight to enable the display to be read in the
dark. The following points should be noted:
♦ The backlight will only function if it is enabled over the IR communications link.
♦ The backlight only operates for a short period after the button is pressed. This
is to conserve battery life.
♦ When the backlight is enabled but currently off, the first short press of the button
serves only to activate the backlight and does not cause a change of display
selection. This may cause confusion in bright day-time conditions when the
EPD TECHNICAL HANDBOOK Page 13
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EPD/HB/40521/000
backlight effect is not apparent and the user may assume that a button press
operation has somehow been ‘lost’.
♦ The backlight activation causes a temporary alarm muting effect, see section
3.2.5.
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Figure 3.2 - LCD Display Segments
3.2 Audible And Visible Alarms
3.2.1 Alarm features
Overview
The EPD contains a sounder and alarm LED (see
Figure 3.1), which are activated together when
certain alarm conditions occur. Alarms are also
indicated in various ways on the LCD. Under
alarm conditions the LED illuminates red and the
sounder sounds at 4 kHz or 2 kHz with an intensity
of between 98 to 101 dBA (4 kHz Loud) at 20 cm.
It is possible to disable the sounder and/or LED so that only one or neither will
activate, but alarm flags on the LCD remain until the condition is normalised. The
alarm sounder can be configured for quieter operation, for example, for office or
hospital environments.
Alarms are acknowledged by pressing the button (long press). This action will
extinguish the alarm LED and mute the sounder. It is possible to disable the mute
function, via the EPD IR communications link (see section 3.2.5).
Note that certain operations and events will automatically mute the audible alarm for
a short period, because of the high electrical current required. These are as follows.
The period of interruption to the sound output is also given:
Operation or event. Typical mute period.
Figure 3.1 - Alarm LED
And Sounder
Communication over the IrDA link 1 second or more, depending upon the
Communications over the
teledosimetry link.
Backlight activated (from the button). Default display timeout ( typically 10
Battery test ( typically every 15
minutes ).
EPD TECHNICAL HANDBOOK Page 16
application.
Less than a second.
seconds ), during which the backlight is on.
Less than 1 second.
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EPD/HB/40521/000
Alarm Configuration
The EPD is able to initiate alarms for a number of different operational conditions.
The nature of any alarm is shown on the LCD display by an alarm flag (see Figure
3.2) or, in the case of an over-range alarm, by a flashing LCD display. Faults are
shown as a letter ‘F’ followed by 3 digits.
There are a number of options that can be set for each alarm, for example, tone,
frequency and volume. The various options are defined in Tables 3.1 and 3.2. The
sounder, LED and mute facilities can only be configured via the IR communications
link. The configurations can be set independently for each alarm event recognised by
the EPD ( see Table 3.3 ).
Note that alarm duration is se t in increments of 4 seconds. Assuming an alarm is not
acknowledged then following this period the alarm is replaced by a single beep every
30 seconds. This feature avoids wasting battery power. The timeout can be disabled
if desired and the alarm output is not then so curtailed.
Alarm Feature Configuration
Alarm Sound
Options
Off
Volume Loud*/Quiet Continuous Single Tone
LED Enabled/Disabled Continuous Dual Tone Slow
Sound Enabled/Disabled Continuous Dual Tone Fast
Tone High*/Low frequency Intermittent Single Tone Slow
User Silence
Enabled/Disabled Intermittent Single Tone Fast
(Mute)
Alarm Sound Options (table 3.2) Intermittent Double Beep Slow
Duration Continuous (0) or up
Intermittent Double Beep Fast
to 17 minutes
Table 3.1 - Alarm Configuration Options
Table 3.2 - Alarm Sounds
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Note: High Frequency = 4 kHz (approximately)
Low Frequency = 2 kHz (approximately)
* To obtain the loudest alarm output it is necessary to configure the
alarm to Loud and High frequency.
The different alarm events identified by the EPD are listed in Table 3.3. This table
also shows the default alarm configurations set by Thermo Electron at manufacture.
The following alarms are regenerated after a reset (e.g. battery change):
• Over Range Alarm
• Dose Alarms
• Return Alarm
• Battery Alarm ( after 1 minute )
• Dose Rate Alarm ( if the condition persists )
Alarm Priorities
It is possible for more than one alarm condition to prevail at any one time. In this
event the sounder output is determined by the highest priority prevailing alarm.
Alarms are prioritised as defined in Table 3.3, Priority 1 being the highest priority.
An active alarm can be superseded by the following events:
• A higher priority alarm is activated ( the new alarm starts ).
• The user mutes alarms with a long button press ( all mute-able alarms are
muted ).
• Alarms are cleared via the communications links.
• A self-cancelling condition de-activates the alarm ( e.g. falling dose -rate ).
Care should be taken if the alarm configurations are altered from the defaults set by
Thermo Electron and the following points should be noted:
1. The alarm priorities are fixed and cannot be altered by the user.
2. If the Alarm Type is OFF, or both LED and Sounder are disabled, then the alarm
type is effectively removed from the list.
3. If the LED (or sounder) only is disabled then the LED (or sounder) output for an
active lower priority alarm will be masked ( not output ).
4. A short duration high priority alarm can curtail the output of a long duration low
priority alarm.
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In general therefore the higher priority alarms should not be configured with
either a short duration, or with LED or sounder disabled, unless the lower
priority alarms are also configured this way.
Priority Alarm/Event Alarm Tone Frequency Volume
1 EPD Failure Alarm. Intermittent Single Slow Tone
__ __ __ __
2 Over-range Alarm. Continuous Dual Fast Tone
_-_-_-_-_-_
3 Hp (10) Dose Alarm
(2)
4 Hp (0.07) Dose
Alarm
5 Hp (10) Dose Alarm
(1)
6 Hp (10)/h Dose Rate
Alarm (2)
7 Hp (0.07)/h Dose
Rate Alarm
8 Hp (10)/h Dose Rate
Alarm (1)
Continuous Single Tone
____________
Continuous Single Tone
____________
Continuous Single Tone
____________
Continuous Single Tone
____________
Intermittent Single Fast Tone
_ _ _ _ _ _
Intermittent Single Fast Tone
_ _ _ _ _ _
High Loud
High/Low Loud
High Loud
High Loud
High Loud
High Loud
High Loud
High Loud
9 Battery Alarm Intermittent Single Slow Tone
10 Return Alarm Intermittent Single Slow Tone
11 Count Down Alarm Continuous Single Tone
12 Abuse Alarm Intermittent Single Slow Tone
EPD TECHNICAL HANDBOOK Page 19
__ __ __ __
__ __ __ __
____________
__ __ __ __
Table 3.3 - Default Alarm Tones
ISSUE 5
Low Quiet
Low Quiet
High Loud
Low Quiet
EPD/HB/40521/000
3.2.2 Dose Alarms
Dose alarms are checked and updated every second, except at low dose rates
where this period increases to a maximum of 14 seconds. Alarms can be adjusted
or inhibited via the IR communications link.
Dose alarms are calculated against a preset alarm threshold set in the EPD. When
the dose equals or exceeds the dose threshold the LED will illuminate, the sounder
will activate and the appropriate alarm flag on the LCD will be displayed. Note that it
is dose and not total dose that is compared with the threshold.
The alarm may be muted by pressing and holding the button, unless alarm mute (user
silence) is inhibited.
The four most significant digits of the alarm thresholds can be viewed on the EPD
LCD and changed using the function button (see Section 3.5.8).
3.2.3 Dose Rate Alarms
Dose rate alarms are checked and updated every second, except at low dose rates
where this period increases to a maximum of 14 seconds. Alarms can be adjusted
or inhibited via the IR communications link.
The dose rate alarms can be made to work with hysteresis, i.e. the alarm 'off'
threshold is lower than the alarm 'on' threshold. The alarm 'off' threshold can be set in
the EPD over the same range as can the alarm 'on' threshold. As the dose rate rises
above the alarm 'on' threshold the LED will flash and the sounder is activated (see
Figure 3.3). The alarm may be muted by pressing and holding the button, unless
alarm mute (user silence) is disabled. The alarm will self-cancel when the dose rate
falls below the alarm 'off' threshold.
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Figure 3.3 - Dose Rate Alarm Example
The four most significant digits of the alarm ‘Off’ and the alarm 'On' thresholds can be
viewed on the EPD LCD and, if user has authority to modify the thresholds, changed
using the function button (see Section 3.5.9).
3.2.4 Over-Range Indication
If a dose rate exceeds 1Sv/h, or if a dose store increments above 1.0Sv, an overrange alarm will occur. The sounder (if enabled) will sound and the LED will flash (if
enabled). The over-range alarm will also cause the LCD display to flash every
second.
Notes:
1. The over-range alarm condition is latched and the LCD will continue to flash
even after a temporary dose -rate over-range condition has cleared. The overrange conditions are recorded in the EPD EEPROM and must be cleared
over the IR communications link before the display will stop flashing.
2. The over-range alarm can be muted ( if enabled ). The EPD will not recur
after muting should over-range conditions re-occur (e.g. in the case of a
second dose-rate over-range alarm ), until the latched condition has been
cleared over the IR communications link. However the LCD will continue to
flash.
3. Th e ADS dose over-range alarm only operates if the unit is ADS issued.
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3.2.5 Alarm Muting
Alarm conditions cause the sounder to be activated and the alarm LED to illuminate,
subject to these facilities being enabled for the alarm. The appropriate LCD alarm
flag is always activated. The user can silence ( mute ) the alarm by pressing and
holding the button, provided mute is enabled on the alarm. This will also extinguish
the Alarm LED. However the LCD alarm flag remains set until such time as the
alarm condition is cleared.
Dose rate alarms are self muting when the dose rate falls below the alarm ‘off’
threshold level. Similarly dose alarms are self muting if the dose is cleared or the
thresholds suitably increased over the IR communications link.
Note that if the display backlight is enabled a short press of the button turns the back -
light on and temporarily silences any active alarm. This is because the EPD unit
battery cannot supply sufficient current for both backlight and sounder together. After
the display timeout period the backlight is automatically turned off and the sounder
re-enabled. Thus a short press may appear to mute the alarm and confuse the user
under such conditions. It is necessary therefore for the user to remember that a long
press is required to mute the alarm.
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3.3 Button Operation and Display Selection
The EPD will display a range of data to the user. The data displayed is selected by
use of the button. The full range of displays is arranged on a two dimensional grid,
as shown in Figure 3.4. There are a number of menus, each having a top-level
display. Menus are changed by holding down the button (Long Press). This
navigates the user down the left hand side of Figure 3.4. Once the desired menu has
been reached the button must be released. Then, by a series of short presses, the
user can navigate across Figure 3.4 until the desired display within the current menu
has been reached.
Any displays that are disabled are removed from the sequence. Some displays are
usefully disabled if their retention might confuse the wearers of the EPD. Other
displays should be disabled if their retention might cause an operational risk, for
example, the ability to zero dose or adjust alarm thresholds. Such display
configuration is easily done using the EasyEPD2 software package. A batch write
facility is available in EasyEPD2 to enable the speedy configuration of a number of
EPD units.
Some displays allow the user to change the status or operation of the EPD. For
example, the user can start, stop and reset the countdown timer. In general, these
operations are activated by “double-pressing” the button. To prevent unwanted user
intervention (e.g. to prevent the user resetting count-down timer) the EPD can be
configured to disable any (or all) of the displays shown in Figure 3.4. Display
configuration changes can only be carried out via the IR communications link.
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EPD/HB/40521/000
3.4 LCD Display Lock-on Facility
Any new display selected using the button remains visible for a set period of time,
(Thermo Electron default time-out is 10 seconds), before returning to the default
display. Some display selections (marked * in Figure 3.4) can be ‘locked -on’, i.e. the
return to the default display is suspended. This facility is especially useful when
displaying dose-rate or when using the count down alarm. If a lock-on facility is
available it must be accepted quickly - when a colon (:) appears just before the
selected display times-out. The colon will only appear for approximately two
seconds. To accept the lock -on facility, press the button when the colon appears. If
the lock-on facility is not required, allow the selected display to time-out. To deselect
the lock-on facility press the button. The display will move on to the next display
selection but will thereafter revert to the default display after time -out.
The seconds count -down timer lock-on facility operates in a slightly different manner
to that described abo ve. In this instance the lock-on facility is available when the
colon disappears. This only occurs for the count -down timer display and, again, is
just before the display times out. To accept the lock -on facility, press the button when
the colon disappears. If the lock-on facility is not required, allow the selected display
to time-out.
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EPD/HB/40521/000
Top-Level Display
Sub-Displays
Button Operation: Long- Next Menu or Mute Alarm
Menu
0
Blank
1
H10 Doses
2
H07 Doses
3
Total Doses
4
Countdown
Timer
5
Power Saving
6
Peaks
(Rate High)
7
Test
8
Clear
9
Dose Alarm
Thresholds
10
Dose Rate
Alarm ON
Thresholds
(Rate On)
11
Dose Rate
Alarm Off
Thresholds
(Rate Off)
12
Sound
Settings
Display:0
HP10
HP07
t0t
5EC5
0n
OFF
r Hi
tE5t
CLr
d AL
r on
roFF
bEEP
1 2 3 4
Button Operation: Short- Next display or lock-on
H10 Dose
H07 Dose
Total H10
Dose*
Count-down
Times
MM:SS
Peak H10
Dose Rate
H10 and H07
Dose Clear
Clr?
1st H10
Dose Alarm
1st H10
Dose Rate
Alarm
ON
1st H10
Dose Rate
Alarm
Off
Button Bleep
Enable/
Disable
H10 Dose
Rate *
H07 Dose
Rate
Total H07
Dose*
Reset
rSt
Peak H07
Dose Rate
2nd H10
Dose Alarm
2nd H10
Dose
Rate Alarm
ON
2nd H10
Dose Rate
Alarm
Off
Chirp Dose
Adjustment
User ID digits
5,6,7,8
ADS User ID
digits 1,2,3,4
H07
Dose Alarm
H07 Dose
Rate Alarm
ON
H07 Dose
Rate Alarm
Off
Internal
Counters
Display* * = Lock-on
User ID digits
1,2,3,4
ADS User ID
digits 5,6,7,8
5
User ID digits
9,10,11,12
ADS User ID
digits 9,10,11,12
EPD TECHNICAL HANDBOOK Page 25
Figure 3.4 - LCD Display Selections
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EPD/HB/40521/000
3.5 Display Options and Button Functions
The following sections describe typical displays that a user may see within each of
the menus shown in Figure 3.4. This description assumes that all displays are
enabled. The user may have access to any (or none) of the displays, depending on
how the EPD has been configured. To call up a top-level display, press and hold the
button until the relevant top-level display appears. Any sub -displays are selected
either by short-pressing, or double-pressing, the button within the display default
time-out.
3.5.1 Displaying Hp (10) Dose, Dose Rate and User ID.
To display Hp(10) doses, press
and hold the button until this toplevel display appears:
Three sub-displays are available (in the following sub-display order):
♦ Hp (10) Dose
♦ Hp (10)/h Dose Rate
♦ User ID Digits
Hp (10) Dose Display
Short-press the button to display the
current dose. This dose parameter is
used for tactical dose monitoring (e.g.
per task etc.).
Display Range: 0µSv to >16Sv (auto
ranging)
Note: Over-range (> 1.0 Sv) is indicated with a flashing LCD display.
Hp(10)/h Dose Rate Display
Short-press the button again to display
the current Hp(10)/h dose rate. Only
the first two significant figures of the
dose rate are displayed, the actual
reading is rounded down.
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EPD/HB/40521/000
Display Range: 0µSv/h to >4Sv/h (auto ranging)
Note: Over-range (> 1.0 Sv/h) is indicated with a flashing LCD display. This
condition is latched to warn the user that the dose value may be inaccurate.
User ID Digits
Short-press the button again to display the user identity number (User ID). This is a
12-digit number that is shown on three separate displays - the High 4 digits, the
Middle 4 digits and the Low 4 digits. Short -press the button to display each of the
remaining User ID digit displays. The User ID cannot be changed using the button.
By convention a non-issued EPD is given a User ID = FFFFFFFFFFFF. Typically, a
User ID will have fewer than 12 digits, but it must be an integer between 1 and
999999999999. For example, a User ID = 9012 will be shown on the LCD display
as follows:
(First Display) (Second Display) (Third Display)
In systems using 8 or fewer digits for the User ID it is usual to disable and thereby
remove the unused displays ( e.g. the first and second display in the above example).
3.5.2 Displaying Hp(0.07) Doses, Dose Rate and ADS User ID
To display Hp(0.07) doses, press
and hold the button until this toplevel display appears:
Three sub-displays are available (in the following sub-display order):
♦ Hp(0.07) Dose
♦ Hp(0.07)/h Dose Rate
♦ ADS User ID Digits
Hp(0.07) Dose Display
Short-press the button to display the
current dose. This dose parameter
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EPD/HB/40521/000
is used for tactical dose monitoring (e.g. per task etc.).
Display Range: 0µSv to >16Sv (auto ranging).
Note: Over-range (> 1.0 Sv) is indicated with a flashing LCD display.
Hp(0.07)/h Dose Rate Display
Short-press the button again to display
the current Hp(0.07)/h dose rate. Only
the first two significant figures of the
dose rate are displayed, the actual
reading is rounded down
Display Range: 0µSv/h to >4.0Sv/h (auto ranging).
Note: Over-range (> 1.0 Sv/h) is indicated with a flashing LCD display. This
condition is latched to warn the user that the dose value may be inaccurate.
ADS User ID Digits
An additional User ID is provided, called Approved Dosimetry Service (ADS) User
ID. This is password-protected and is used by ADS systems for “permanent” issue
EPDs. The ADS User ID may be displayed in a similar fashion to the User ID.
Short-press the button again to display each of the remaining ADS User ID digit
displays. A non-issued EPD may have an ADS User ID = FFFFFFFFFFFF.
Typically, an ADS User ID will have fewer than 12 digits, but it must be an integer
between 1 and 999999999999. For example, an ADS User ID = 3324 will be shown
on the LCD display as follows:
(First Display) (Second Display) (Third Display)
In systems using 8 or fewer digits for the ADS User ID it is usual to disable and
thereby remove the unused displays ( e.g. the first and second display in the above
example).
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3.5.3 Displaying Total Dose
To display total dose, press and
hold the button until this top -level
display appears:
Two sub-displays are available (in the following sub-display order):
♦ Hp(10) Total Dose
♦ Hp(0.07) Total Dose
Hp(10) Total Dose
Short-press the button to display
the total Hp(10) dose.
Display Range: Hp(10) 0µSv to >16Sv
(auto ranging).
Hp(0.07) Total Dose
Short-press the button again to
display the total Hp(0.07) dose.
Display Range: Hp(0.07) 0µSv to >16Sv (auto ranging).
Each display represents a record of the total dose received by the EPD over multiple
tasks (e.g. per day, per week etc.).
3.5.4 Starting/Stopping The Seconds Count Down Timer
To start/stop the seconds countdown timer, press and hold the
button until this top-level display
appears.
Two sub-displays are available (in the following sub-display order):
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EPD/HB/40521/000
♦ Count-down Time MM:SS
♦ Reset (rSt)
The count-down timer is a useful facility for activities where actions need to be
completed within known time periods. The User may start, stop and reset the count
down timer using the button. When the timer expires the appropriate alarm is
sounded. The count down time period is pre-set and can only be adjusted via the IR
communications link.
Count-Down Time
Short-press the button to display the
‘Count-Down Time’ (which indicates the
count down time period, or the remaining
count down time available).
Double-press the button to start the digits counting down to zero. The display is in
units of minutes and seconds. The maximum count down time available is 99
minutes, 59 seconds.
The count down function continues when the display reverts to the default display
after the display timeout period. However it is useful to ‘lock on’ to this display as
described in section 3.4.
Stopping the Timer
To stop the timer double-press the button again. The digits will stop decreasing.
Reset
Short-press the button to select the
display shown opposite. Double press
the button and the display will flash.
Double-press the button again to confirm the reset (the display will show the reset
time at its reset value). The timer may now be started as described above.
3.5.5 Turning the EPD off
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EPD/HB/40521/000
To turn the unit off, press and hold the
button until the word ‘On’ appears:
Only one sub-display is available:
♦ On/Off
This function enables the EPD to be placed in sleep or OFF mode. In OFF mode
power consumption is reduced considerably and the EPD stops measuring
radiation.
Assuming that the display shows On, double-press the button. The display will
change to “OFF” (flashing). Double-press the button again to confirm the request.
The display will change to the word “OFF” (not flashing), confirming that the unit is in
OFF mode and not measuring radiation.
To return to operating mode press and hold the button. The display will revert to the
default display.
Note: ON/OFF control via the button may be inhibited by the appropriate setting of
the EPD internal configuration via the IR communications link.
3.5.6 Displaying Peaks (Rate High)
To display peaks (high rate),
press and hold the button until
this top -level display appears:
Two sub-displays are available (in the following sub-display order):
♦ Peak Hp(10)/h Dose Rate
♦ Peak Hp(0.07)/h Dose Rate
These displays show the highest dose rate that the EPD has measured since the
peaks were last cleared. The peak dose rates measured are recorded for
penetrating and superficial dose rates, together with the times at which these rates
occurred (to a resolution of 1 second).
Peak Hp(10)/h Dose Rate
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EPD/HB/40521/000
Short-press the button to display the
Peak Hp(10)/h Dose Rate:
Peak Hp(0.07)/h Dose Rate
Short-press the button again to
display Peak Hp(0.07)/h Dose
Rate:
Note: Peaks can only be cleared via the IR communications link.
3.5.7 EPD Confidence Test
To perform the EPD confidence test,
press and hold the button until this
top-level display appears:
Only one sub-display is available:
♦ Test
This test can be run at any time during operational use as a confidence check that
the EPD is functioning correctly. Throughout the confidence test the heart-beat
(activity) indicator flashes once per second. The confidence test can be stopped at
any time by pressing the button.
Note: During the EPD confidence test a brief detector test is performed, during
which dose accumulation is momentarily inhibited.
Double-press the button. The EPD will commence its confidence test routine, as
follows:
1. The all-segment display is displayed for approximately 5 seconds. This
allows the user to check that all segments are functional (see Figure 3.2).
2. The alarm will sound and the LED will flash for approximately 2 seconds. This
indicates that the sounder and LED are functional.
3. The all-segment display will disappear. The alarm will continue to sound and
the LED will continue to flash, at an increased rate, for approximately 6
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EPD/HB/40521/000
seconds. This indicates that the LCD segments can be turned off, and that
the tone frequencies are functional.
4. The all-segment display will reappear for approximately 5 seconds and the
LED will slow flash.
5. The all-segment display will disappear and the default display will appear.
This indicates that the confidence test has been successfully completed and
that the EPD is ready for operational use.
Upon completion of the confidence test, the unit reverts to the default display. If the
confidence test is unsuccessful a letter ‘F’ followed by three digits is displayed. Note
the failure codes and refer to Section 5 (Failure Modes and Fault Diagnosis).
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3.5.8 Clearing Dose Displays
To clear dose displays, press and
hold the button until this top-level
display appears:
Only one sub-display is available
♦ Clr?
This mode is used to clear the Hp(10) and Hp(0.07) doses.
Note: The total doses are not cleared.
Press the button once to select the
display shown opposite.
Double-press the button again and the display will flash. Double-press the button
again to confirm the request. The display will change to 0000 and return to the
default display. The Hp(10) and Hp(0.07) doses have now been cleared.
3.5.9 Displaying/Setting Dose Alarm Thresholds
To display and/or set dose
alarm thresholds, press and
hold the button until this toplevel display appears:
Three sub-displays are available (in the following sub-display order):
♦ 1st Hp(10) Dose Alarm
♦ 2nd Hp(10) Dose Alarm
♦ Hp(0.07) Dose Alarm
The EPD can be used as a ‘personal alarming’ dosemeter, with alarm thresholds for
accumulated dose alarms. This mode displays the current settings for the dose
alarm thresholds. The alarm threshold can be modified by the user, if required, but
only when the default setting is set to ‘adjustable’. The user is barred from modifying
the threshold if the default is set to ‘not adjustable’. These default settings can only
be set via the IR communications link.
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There are two Hp(10) alarm thresholds and a single Hp(0.07) alarm threshold that
can be displayed and modified. The 2nd Hp(10) dose alarm has the higher priority
and should always be set to a higher value than the 1st Hp(10) alarm. The
accumulated dose alarm thresholds can be set using the button as follows:
1st & 2nd Hp(10), Hp(0.07): 10µSv, 50µSv, 100µSv, 500µSv, 1mSv, 5mSv,
10mSv, 50mSv, 100mSv, 500mSv, 1.0Sv.
Example of 1st Hp(10) Dose alarm
threshold display set at a default
value of 500 µSv:
Other values for the dose alarm thresholds may be set via the IR communications
link.
Changing The Dose Alarm Thresholds
To change the 1st Hp(10) dose
alarm threshold select the display
above and double-press the button.
The display will change to the
following with the digits flashing:
Alarm Set Limits: 10µSv to 1Sv.
Pressing the button will increase the alarm threshold in the following steps: 10µSv,
50µSv, 100µSv, 500µSv, 1mSv, 5mSv, 10mSv, 50mSv, 100mSv, 500mSv, 1.0Sv.
When the required threshold is reached double-press the button to confirm the value
and the flashing display will stop.
If you start to change the threshold and change your mind this option can be aborted,
as follows:
Short-press the button until the
following is displayed (letters
flashing). Double-press the button to
confirm that you wish to escape and
return to the previous alarm
threshold.
If the “ESC” screen is displayed and the button is not pressed, after default time -out
the display will return to the dose alarm threshold that was being set-up. Again, if the
button is not pressed, the display will return to the default screen after a further timeout period.
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3.5.10 Displaying/Setting Dose Rate Alarm On/Off Thresholds
To display and/or set dose rate
alarm ON thresholds, press and
hold the button until this top-level
display appears:
Three sub-displays are available (in the following sub-display order):
♦ 1st Hp(10)/h Dose Rate Alarm ON
♦ 2nd Hp(10)/h Dose Rate Alarm ON
♦ Hp(0.07)/h Dose Rate Alarm ON
To display and/or set dose rate
alarm OFF thresholds, press the
button until this display appears:
Three sub-displays are available:
♦ 1st Hp(10)/h Dose Rate Alarm OFF
♦ 2nd Hp(10)/h Dose Rate Alarm OFF
♦ Hp(0.07)/h Dose Rate Alarm OFF
The EPD can perform the role of a ‘personal alarming’ EPD with alarm thresholds for
dose rate. There are two Hp(10)/h dose rate alarms and a single Hp(0.07)/h dose
rate alarm that can de displayed. The 2nd Hp(10)/h dose alarm has the higher priority
and should always be set to a higher value than the 1st Hp(10)/h alarm. The alarm
thresholds can be modified by the user, if required, but only when the EPD default
setting is set to ‘adjustable’. The user is barred from modifying the thres holds if the
EPD default is set to ‘not adjustable’. These default settings can only be set via the
IR communications link.
The dose rate alarm thresholds can be set using the button as follows:
10µSv/h, 50µSv/h, 100µSv/h, 500µSv/h, 1mSv/h, 5mSv/h, 10mSv/h,
50mSv/h, 100mSv/h, 500mSv/h, 1.0Sv/h
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Other values for the dose rate alarm thresholds may be set via the IR
communications link.
Note: To avoid false alarms due to counting statistics it is recommended that the
Hp(0.07)/h dose rate alarm is not set to less than 100µSv/h
Example 1st Hp(10)/h dose rate on
alarm threshold display set at a default
value of 500 µSv/h:
'On' and 'Off' alarm thresholds allow hysteresis for dose rate alarms, see section
3.5.1. If hysteresis is not to be used the ‘On’ and ‘Off’ thresholds should be set to the
same value.
Changing the Dose Rate Alarm Thresholds (ON and OFF):
To change the 1st
on alarm threshold, for example,
select the above display and double press the button. The display will
change to the following and the digits
will flash:
Alarm Set Limits: 10µSv/h to 1Sv/h
Pressing the button will increase the alarm threshold in the following steps: 10 µSv/h,
50µSv/h, 100µSv/h, 500µSv/h, 1mSv/h, 5mSv/h, 10mSv/h, 50mSv/h, 100mSv/h,
500mSv/h, 1.0Sv/h. When the required threshold is reached double -pressing the
button to confirm the value and the flashing display will stop.
(10)/h dose rate
H
p
If you start to change the threshold and change your mind this option can be aborted,
as follows:
Short-press the button until the
following is displayed (letters
flashing). Double -press the button to
confirm that you wish to escape and
return to the previous alarm threshold.
If the ‘ESC’ screen is displayed and the button is not pressed, after default time-out
the display will return to dose alarm threshold that was being set-up. Again, if the
button is not pressed, the display will return to the top level default screen after a
further time out period.
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Notes:
1. The ‘On’ threshold must always be greater than or equal to the ‘Off’ threshold.
2. If an attempt is made to set the ‘On’ threshold below the ‘Off’ threshold the
‘Off’ threshold will be set automatically to the same value as the ‘On’ threshold.
3. If an attempt is made to set the ‘Off’ threshold above the ‘On’ threshold the
‘Off’ threshold will be set automatically to the same value as the ‘On’ threshold.
3.5.11 Setting The Sounder
To change the EPD sounder
settings, press and hold the
button until this top-level
display appears:
Three sub-displays are available (in the following sub-display order):
♦ Button Beep Enable/Disable
♦ Chirp Dose Adjustment
♦ Internal Counters Display
Note: This option will not enable/disable the alarm sounder. Enabling/disabling the
sounder under alarm conditions can only be set via the IR communications link
(see Section 3.2.4).
Button Beep Enable/Disable
The EPD can be configured to beep every time the button is pressed. This feature
may be toggled 'on' and 'off' via the button, or via the IR communications link (i.e.
EasyEPD2).
Note: If the button beep has been disabled via the button any subsequent
initialisation of the EPD will revert the button beep to ON (enabled). If the button
beep has been disabled via the IR communications link, the button beep will remain
disabled regardless of any subsequent EPD initialisation.
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Short-press the button to display the
button beep enable/disable window.
To configure the beep feature 'off' or
'on' double-press the button while the
EPD is displaying the following
displays. Button Beep Enabled
Button Beep Disabled
Dose Chirp Adjustment
The EPD can be configured to give a warning chirp at every preset increment in
Hp(10)/h, penetrating (deep) dose. This increment can be set between 0.01µSv and
100µSv, or disabled by setting the increment to 0.
Short-press the button to display the
current dose per chirp:
An increment set to 1µSv is shown
opposite. With a chirp sensitivity of
1µSv/chirp and a dose rate of 10mSv/h the
sounder will average 2.8 chirps every
second.
To change the chirp rate, doublepress the button at current dose
chirp display. The display digits will
flash.
Dose Chirp Limits: 0.01 µSv to 100µSv.
Note: 0 = Off ( no chirp function ).
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Pressing the button will increase the dose per chirp in the following increments:
0.0µSv, 0.01 µSv, 0.05 µSv, 0.1µSv, 0.5µSv, 1.0 µSv, 5µSv, 10µSv, 50 µSv, 100µSv.
When the required sensitivity is reached “double-pressing” the button will confirm the
value and the flashing display will stop.
If you start to change the sensitivity,
and change your mind, the option can
be aborted. Short-press the button
until the following is displa yed (letters
flashing).
Double-press the button to confirm you want to return to the previous chirp sensitivity.
To switch off the dose chirp double-press the button when 0.0 µSv is displayed.
If the “ESC” screen is displayed and the button is not pre ssed, after default time -out
the display will return to dose chirp adjustment display. Again, if the button is not
pressed, the display will return to the top level default screen after a further time out
period.
Internal Counters Display
Short-press the button to display the
current internal counters display.
The display is in hexadecimal format and shows the last digit of: hard gamma (HG),
soft gamma (SG), full beta (FB) and beta compensation (BC) count s respectively.
This display is intended for test purposes and may be useful for identification of faults
or operational problems.
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SECTION 4
TECHNICAL DESCRIPTION
This section provides a technical description of the EPD and contains a summary of
the EPD’s radiological features together with a summary of the EPD’s electrical,
mechanical and environmental characteristics.
4.1 General
The EPD is of rugged construction and is suitable for most conditions that can
reasonably be expected in industrial environments. The radiological features of the
EPD are summarised below (a full radiological specification is given in Appendix A
to this handbook):
♦ Sensitivity to X and γ radiation, β particles
♦ Multiple PIN diode detectors
♦ 4 channel parametric algorithm processing
♦ Direct readout of personal dose equivalents Hp(10) (penetrating/deep/whole
body) and Hp(0.07) (superficial/shallow/skin)
♦ Neutron response <2%
♦ Meets relevant parts of BS-EN-ISO61526 for dose equivalent monitors
(unless otherwise specified)
♦ Dose display and storage 0µSv to >16Sv (0.0 mrem to > 1600 rem) auto
ranging
♦ Resolution for dose display 1µSv (0.1mrem) at levels up to 10mSv (1 rem)
♦ Resolution for dose storage 1/64µSv
♦ Dose rate display 0µSv/h to >4Sv/h auto ranging, resolution 2 most significant
digits or 1µSv/h at lower levels (10µSv/h for Hp(0.07)/h)
♦ Dose rate peak store 0µSv/h to >4Sv/h resolution 1µSv/h
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4.2 Electrical Description
4.2.1 Electrical Characteristics
Power Supply: One AA Lithium Thionyl Chloride (LTC) battery 3.6 V), giving
typically 5 months continuous operation at an average dose
rate <5µSv/h with the alarm sounding <5 hours total during
battery life.
or:
One standard AA Alk aline battery (1.5 V), giving typically 55
days continuous operation at an average dose <5µSv/h with
the alarm sounding <2 hours total during battery life.
Confidence Test: Activated on start-up and by the button when the
CONFIDENCE TEST mode is called-up (see Section 3.5.7).
Detector Test: Performed during the start-up sequence and as a
background test, and under demand via the IR interface.
Battery Test: Configurable time interval between 1 to 60 minutes.
(15 minutes recommen ded).
Alarm sounder : 98 dB(A) to 101 dB(A) at 20 cm (loud mode)
75 dB(A) to 85 dB(A) at 20cm (quiet mode)
with multiple modes.
4.2.2 Battery Management
The EPD circuitry is designed to operate at 3.6V DC. The EPD can be powered by
either a 3.6V Lithium Thionyl Chloride (LTC) (Sulphurous Oxychloride, SOCL2)
battery or a standard 1.5V AA Alkaline type battery. If a 1.5V Alkaline battery is
installed the EPD automatically switches -in a step -up converter to maintain the 3.6V
operating voltage. The step-up converter is also switched in as the LTC battery runs
down. However, the EPD will not start up if it is fitted with a LTC battery that has been
discharged sufficiently to require the step-up converter to operate.
Operationally, as the voltage from either battery type falls, a series of preset voltage
thresholds operate as follows:
(i) The internal step-up converter is switched in to mainta in the voltage at the
EPD’s operating level.
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(ii) As the battery voltage under load continues to fall, the low battery alarm flag is
activated to indicate when a minimum of 10 hours battery life is remaining.
Different thresholds are automatically select ed for LTC or alkaline batteries.
(iii) As the battery voltage under load finally falls below tolerance the EPD resets
(blank display). The EPD battery must be replaced.
The EPD software runs an internal battery condition test at regular intervals (between
1 and 60 minutes). This time interval is factory preset to 15 minutes and can be
adjusted via the IR communications link. 15 minutes is the preferred interval.
The EPD has an ON/OFF power saving facility, in which the detectors are turned off,
which is intended for short-term storage (e.g. overnight). In the power saving mode
the LCD will display OFF (i.e. the EPD is off - see also Section 3.5.5). In the EPD
OFF condition battery drain is reduced to approximately 20% of the drain when the
EPD is in the ON condition (i.e. fully operational). The EPD does not measure
radiation when it is OFF.
Additional information and warnings relating to the EPD battery are given in Section
6.2.
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4.3 Mechanical Description
4.3.1 Mechanical Characteristics And Dimensions
Display and function control: Single button on the front of the EPD (recessed
to prevent inadvertent operation).
Case material : High impact Polycarbonate/ABS blend.
Clip : High impact plastic clip assembly comprising:
♦ spring clip
♦ lanyard plate,
Weight : 95 gm including LTC battery and clip.
88 gm with lanyard plate only (clip removed).
Dimensions : See Figure 4.1.
4.3.2 Brief Mechanical Description
The EPD is of semi -modular construction and comprises an inner conductive liner,
an outer case assembly and lid. The inner liner houses the EPD’s electronic
components. The outer case, consisting of a moulded front and back, fits around the
inner liner and is fused together to provide physical protection. The lid, which is fitted
to the top of the outer case, has a tight tolerance and is locked in place as an integral
part of the EPD assembly. The outer case and lid are designed not to come apart.
The complete assembly is engineered to house functional and operation
components (e.g. EPD battery, LCD display, button, alarm LED, alarm sounder, IR
communications link and beta window (see Figure 2.1). Externally, the outer case is
contoured to receive, and lock in place, a clip assembly (see Section 6.3).
Essentially, component replacement is limited to the EPD battery, battery cap and
clip assembly.
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Figure 4.1 - EPD Dimensions
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4.4 Environmental Description
4.4.1 Environmental Characteristics
Operating Temperature : -10°C to +40°C.
Storage: -25°C to +70°C.
Humidity: 20% to 90% RH non condensing.
Protection: IP55. Total protection against dust and against low
pressure jets of water from all directions.
Vibration: IEC 1526 2g, 15 min, 10 - 33 Hz
Shock: 1.5 m drop on each surface onto concrete.
EMI/EMC: Exceeds MIL STD 461D RS103 (see Appendix B).
4.4.2 Brief Environmental Description
The EPD is designed for use in the following environments:
♦ Office and Laboratory environment,
♦ Industrial environments,
♦ Hospitals
♦ Military environments (including dockyards and shipping - but excluding
exposure to salt water and extremes in military environment).
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4.5 Infra-red Interface
The EPD contains an infra-red interface (see Figure 4.2) which can optically
communicate (read and write) to PC-based hardware using a suitable infra -red
communications program. This interface is compatible with IrDA level 1 protocol.
Figure 4.2 - EPD Infra-Red Interface
4.5.1 Communicating With The EPD
The EPD electronically stores dose and dose rate data, together with other
information that is required to control and configure the EPD. Communication with
the EPD is essential in order to read data from store and to write data to store so
that EPD parameters, operational control and general functionality can be set.
During the read/write process the EPD can be configured for any (or all) of the
display selections shown in Figure 3.4 to be made available to the user, as required.
Only limited functions can be configured via the EPD button.
On the front of the EPD there is an IR communications link for reading and writing
data. Communication with the EPD is usually via an IR adapter, which is connected
to a host PC. EasyEPD2 is a Thermo Electron PC-based software product for
maintaining, configuring and reading EPDs. The IR communication range is up to
1m, over an angle of ±30° from the normal to the front of the EPD.
After any successful communication via the IR communications link the EPD will
show the default display. There is a time-out from the last communication after which
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the EPD reverts to normal display. There is also an inhibit timer that prevents an
EPD from re-establishing communications immediately after communications are
completed. This gives the user time to remove the EPD from the IR field. The EPD
continues to measure radiation during communication. Communication via the
EPD’s IR communications link will allow access to the following EPD functions and
displays:
♦ Default Display
♦ User Identification
♦ Dose and Dose Rate
♦ Alarms and Alarm Thresholds
♦ Counts
♦ Dose Quality
♦ Control of the EPD
♦ Status
♦ Scratch Pad
♦ Timed Events
♦ Dose Profile
♦ Special Total Dose Store
♦ ADS Issue
♦ Calibration Parameters
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4.6 EPD Internal Processing & Facilities
This section describes the internal processing performed by the EPD and the
facilities provided over the IR communications link.
4.6.1 Memory Characteristics:
Memory Retention: 10-year data retention.
Dose Profile History: Settable interval from two seconds to 35 hours.
Stores transitions of Hp(10) and Hp(0.07) at a
resolution of 1µSv. Store for up to 579 records
for transitions up to 127 µSv or less.
Dose Store (short term): Hp(10) and Hp(0.07). Can be reset after each
controlled area entry, day, month (etc) by health
physics staff or dose management system,
according to local procedures.
Total Dose Store: Separate total dose store.
Special Total Dose Store: 12 entries, e.g. for automatic recording of end
of month dose etc.
Event Log: 23 entries for time recording of alarms etc., for
incident assessments.
ADS Dose Store: Approved Dosimetry Service (Record of Dose)
dose memory area with password protection.
Peak Dose Rates: Peak dose rates with time of occurrence.
Storage Times: 1 second resolution.
Alarm Flags: Various alarm and fault flags.
Timer: Count-down timer configurable up to 1 hour 39
minutes and 59 seconds (1 second resolution).
Return for Read: Programmable warning.
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4.6.2 Alarm Characteristics:
Alarms: 2 each Hp(10) dose and dose rate alarms
1 each Hp(0.07) dose and dose rate alarms
Dose and Dos e Rate Alarms: 0µSv to 16Sv and 0µSv/h to 16µSv/h resolution
V 1/64µSv and 1µSv/h
Recommended minimum settings to avoid
false alarm 7µSv/h Hp(10)/h and 100µSv/h
Hp(0.07)/h
Alarm Types: Audible and visual alarms for dose, dose rate,
count-down timer, read time and failure mode.
Alarms are configurable via the IR
communications link.
Tones: High/low tones, loud/quiet volume in seven
combinations of continuous or fast/slow
intermittent.
Hp(10) Dose Chirp: Settable from 0.01 µSv/chirp to 100 µSv/chirp.
4.6.3 Default Display
The default display is initially factory preset to read Hp (10) (the penetrating or deep
dose), or to an alternative default display as specified by the customer. Userselected displays have a time-out period, which can be set between 10 to 99
seconds. This time -out is the period of time that any display selected by the user will
stay active before reverting to the default display. The time-out period may be
adjusted via the IR communications link. The default display can be changed to any
of the displays shown in Figure 3.4, again, via the IR communications link.
4.6.4 User Identification
The EPD retains details relating to the current user and the number of times that the
EPD has been issued. Wearer details comprise the user’s identification number
(i.e. the User ID) and the User Name The User Name can be a string of up to 22
characters. By convention, an un-issued EPD User ID is set to all ‘F’s
(FFFFFFFFFFFF). Typically, a User ID will have fewer than 12 digits, but it must be
an integer between 1 and 999999999999. A full description of User IDs is given in
Sections 3.5.1 and 3.5.2.
User identification can only be set via the IR communications link.
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4.6.5 Dose and Dose Rate
The EPD calculates dose and dose rate. Dose is accumulated in 3 stores: Dose,
Total Dose and ADS Dose. Dose rate is the current rate calculated by the EPD.
Dose
The EPD displays Hp(10) (penetrating or deep) dose and Hp(0.07) (superficial or
shallow) dose. Dose is regarded as a short-term record of dose received, usually
associated with the issue of an EPD. It is this value that is compared with dose
alarm thresholds and an alarm raised if the value exceeds the thresholds. The EPD
records Dose, Total Dose and ADS Dose in units of 1/64µSv, although this is
displayed as a decimal equivalent. Total Dose is a store providing a long-term
record of dose accumulated by the EPD. The LCD display can be set to auto-
range between 1µSv to 16Sv (maximum resolution 1µSv).
Display characteristics that can be set are:
Units Sv or rem
Decimal Places: 2 or 3 decimal places
Resolution: µSv or mSv
Default Time: 10 to 99 seconds
Note: For Gamma dose, two counts are approximately equivalent to 1/64 µSv and
for Beta dose one count is approximately 1/6µSv. To avoid statistical
inaccuracies doses should only be displayed in micro sieverts (or 0.1 rem),
but when summing a number of doses the full resolution should be used to
minimize rounding errors.
Dose Rate
This is the current dose rate as calculated by the EPD. It may be viewed on the
display or read via the IR communications link. Dose rates are calculated using an
averaging algorithm to reduce statistical variations to within ±20% under most
conditions. This results in inc reased averaging time constants at low dose rates.
Averaging time constants used to calculate penetrating dose rate Hp(10)/h maximise
at 60 seconds below 70uSv/h and therefore the statistical errors increase as the
dose rate drops below 70uSv/h. Additional processing is used to provide faster
response but with reduced accuracy when rapid changes in dose rate are observed.
The algorithm is a compromise that reduces statistical errors but gives a fast
response time. The dose rate displays on the LCD are l imited to 2 significant digits.
Longer time constants have to be used when averaging the beta dose due to the
lower sensitivity of the beta detectors. The time constant used maximises at 100
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seconds below 1mSv/h. Due to limitations in the processing and memory available,
this time constant cannot be reduced when rapid changes are observed, and the
Hp(0.07)/h dose rate is approximated as the sum of Hp(10)/h and the beta dose rate.
This approximation means that at low gamma energies (below 50 keV) the
Hp(0.07)/h dose rate typically under-responds by up to 25% in comparison to the
Hp(0.07) dose response. However, above 25 keV the dose rate response remains
within ±30% accuracy criteria.
Peak Dose Rate
The highest dose rate calculated by the EPD since this value was last cleared is
termed the peak dose rate. The peak dose rates and the times at which these peak
rates occur are recorded and can be displayed on the LCD or read over the IR
communications link.
Note: Peak dose rate times are stored to 1 second resolution.
4.6.6 Counts
The EPD has four internal counters:
♦ HG: Hard Gamma
♦ SG: Soft Gamma
♦ FB: Full Beta
♦ BC: Beta Compensating
These record the pulses output by each of the radiation detectors.
The EPD calculates the Hp(10) and Hp(0.07) doses by weighted summing (ratios set
during calibration) of the counts received on the four detector channels.
Counts can only be read via the IR communications link, although the least significant
digits are visible on the internal counts display ( section 3.5 ).
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4.6.7 Dose Quality Flags
There are 7 dose quality flags set within the EPD. Dose quality can only be read and
cleared via the IR communications link. They are normally cleared at the start of an
Issue period. The dose quality flags are as follows:
(i) Reset Count
The reset count flag is a count of the number of times the unit has been reset, either
by:
(a) removing and re-fitting the battery,
(b) by a commanded reset via the IR communications link,
(c) by a software reset.
(ii) Shock Time Seconds
The EPD detectors are susceptible to large mechanical shocks. This is overcome
by detecting the shock with a piezo detector. The EPD continues to accumulate
dose during the shock period, but at the dose rate that was present immediately
before the shock was detected. However, if the dose rate is greater than
approximately 4mSv/h the counts caused by the shock will be small relative to the
radiation counts and therefore all counts are used in the calculation of dose. Shock
Time is the time period over which shock processing has taken place. Continuous
Shock detection for greater than 45 seconds will cause an abuse alarm (see Abuse
Warning).
(iii) Dose Over-range
The dose over-range flag indicates that one of the dose stores has exceeded 1Sv
(100 rem) . Dose continues to accumulate above this value to a maximum of
16.777215 Sv (1677.7215 rem).
(iv) Dose Rate Over-range
The dose rate over-range flag indicates that the dose rate has exceeded 1Sv/h (100
rem/h) at some time in the past, (i.e. the recorded dose may be inaccurate, probably
low, due to non-linearity at high dose rates).
(v) Counter Over -range
The counter over-range flag indicates that at least one detector has exceeded the
maximum count rate expected (300,000 counts/second - gamma counters and
26,000 counts/second - beta counters). A possible cause for this flag to set is that
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the unit has either been exposed to some kind of extreme interference or has
developed a fault.
(vi) Abuse Warning
The abuse warning indicates that an abuse alarm has been activated. An abuse
alarm is activated if mechanical shocks are detected continuously for greater than 45
seconds (see Shock Time Seconds)
(vii) CRC Failure
The CRC failure flag is set as a result of an integrity check on a set of data indicating
that the EPD detected a checksum error in the dose data. Checksum failures are
corrected by retrieving the last stored dose from secure store (EEPROM). During
the correction process u p to 15 minutes of dose may be lost.
4.6.8 Dose And Dose Rate Alarm Processing
The EPD performs alarm processing as described in this section. The occurrence of
a dose or dose -rate alarm is recorded by the following internal flags. These flags
make it easy for applications s/w to determine over the IR communications link
whether an alarm has occurred during an issue period. The flags are therefore
normally cleared over the IR communications link at the start of an issue period:
♦ Three Dose alarm flags indicate that a dose has exceeded the corresponding
dose alarm thresholds. There are 1st and 2nd dose alarms for Hp(10) and a
single dose alarm for Hp(0.07).
♦ Three Dose rate alarm flags indicate that a dose rate has exceeded the dose
rate alarm thresholds. There are 1st and 2nd dose rate alarms for Hp(10)/h
and a single dose rate alarm for Hp(0.07)/h. The dose-rate flags are not
cleared automatically when the dose-rate falls below the reset threshold.
The 2nd alarm threshold (dose or dose rate) always has a higher priority than the 1st
alarm threshold. The 1st alarm threshold can be considered as a warning value and
the 2nd alarm threshold as a critical value. Therefore, the 2nd alarm threshold should
always be set to the higher value.
Dose rate alarms can be configured to work with hysteresis. That is, the Hp(10)/h 1st
and 2nd dose alarms and the Hp(0.07)/h dose rate alarm are each provided with
separate ON and OFF thresholds. When the dose rate equals or exceeds the alarm
ON threshold the EPD will set an alarm flag and the sounder will sound and the LED
flash (if enabled). The alarm is self-cancelling when the dose rate falls below the
alarm OFF threshold, but the alarm flag remains set.
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Alarm thresholds are set via the IR communications link, or by the button if the user is
granted authority (see Figure 3.4), to any value in the following ranges:
1st & 2
Hp(0.07)/h 0µSv/h to 16.777215 Sv/h
1st & 2nd Hp(10) 1µSv to 16.777215 Sv
Hp(0.07) 1µSv to 16.777215 Sv
It is not recommended to set dose rate alarms to less than 7uSv/h (Hp10)/h or
100µSv/h Hp(0.07)/h as the statistical errors on the dose rate reading at these levels
will be greater than ±50%, and false alarms may occur in normal background
radiation conditions.
4.6.9 EPD Operating Status
The EPD retains information regarding its status. EPD status can only be read via
the IR communications link. Status information provided is:
♦ EPD Run Times
nd
Hp(10)/h
0µSv/h to 16.777215 Sv/h
♦ EPD State
♦ Alarms
♦ Warnings
♦ Faults
♦ Event history
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.
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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)
2. Connection Failed. Communication with the EPD failed.
3. Cal Factors Bad. The EPD calibration factors failed a CRC
4. EEPROM Fail. An un-recoverable EPD secure store failure
5. Bad Sectors. The number of bad EPD secure store sectors.
6. Detector Test Fail. The EPD detector test was run and the number
7. Detector Threshold Fail. The EPD detector thresholds failed to load
has been logged in the EPD’s event store.
check and cannot be recovered from secure
store.
occurred.
There is a maximum of nine spare sectors.
of counts received were less than required to
pass the test.
successfully
8. Radio Fail. Reserved for future use.
9. Other Fault . A fault occurred causing the EPD to reset.
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10 Disabled. The EPD is not calculating dose.
4.6.10 Dose Profile
The EPD stores Hp(10) and Hp(0.07) dose to a resolution of 1µSv in non-volatile
store so that a profile of the dose over time can be recreated. The interval between
stores is set-up via the IR communications link.
Both Hp(10) and Hp(0.07) dose information is stored as a dose profile, the minimum
interval between entries in the dose profile is adjustable between 2 seconds to 35
hours, in 2 second intervals. The store holds up to 579 records for transitions up to
127 µSv or less.
Note: A dose profile interval of zero seconds turns off the dose profile function.
Dose profile can only be read via the IR communications link. Dose profile may be
synchronised to a particular time in the future, e.g. hourly logging on the hour.
Note: The EPD has no concept of real-time but maintains a one-second tick that is
valid as long as the EPD is powered and not reset.
4.6.11 Event History Store
The EPD logs up to 23 events in non-volatile store, together with a time stamp.
These comprise alarm and fault events see tables 4.1 and 5.2.
Note: The Event History time store wraps round after 194 days of operation. After
this time previous event-associated day/date(s) cannot be considered as
accurate. In addition elapsed time during loss of power is not recorded.
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Events On Events Off
Code Text as displayed by
EasyEPD2
200 Failure Alarm on 220 Failure Alarm off
201 Over Range Alarm on 221 Over Range Alarm off
202 Hp10 Dose Alarm 2 on 222 Hp10 Dose Alarm 2 off
203 Hp07 Dose Alarm on 223 Hp07 Dose Alarm off
204 Hp10 Dose Alarm 1 on 224 Hp10 Dose Alarm 1 off
205 Hp10 Rate Alarm 2 on 225 Hp10 Rate Alarm 2 off
206 Hp07 Rate Alarm on 226 Hp07 Rate Alarm off
207 Hp10 Rate Alarm 1 on 227 Hp10 Rate Alarm 1 off
208 Battery Alarm on 228 Battery Alarm off
209 Return for read Alarm on 229 Return for read Alarm off
210 Count Down Alarm on 230 Count Down Alarm off
211 Abuse Alarm on 231 Abuse Alarm off
Code Text as displayed by
EasyEPD2
Other Events
Code Text as displayed by
EasyEPD2
240 Power Converter Switched
On
241 Power Up Cold Start
242 Power Up Warm Start
Table 4.1 ( 3 parts ) EPD Events logged to the Event History Store.
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SECTION 5
EPD FAULTS and RECOVERY ACTIONS
5.1 Overview
This section identifies the fault conditions that can occur and describes the recovery
procedure (if any) to be taken to restore the EPD to operational use.
The section is organised as follows:
1. Fault indication via sounder, alarm Led, LCD.
2. Internal logging of fault conditions.
3. Blank display and other “uncontrolled” faults.
4. Communications Error over the IR link.
5. LCD Display error codes.
6. Recovery Procedures.
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5.2 Visual and Audible Fault Indication
An EPD failure is usually indicated by a visual and audible alarm. In most instances
the EPD will display an error code on the LCD and the LED will flash. The default
audible alarm is as follows:
Alarm rate:
If alarm mute is enabled for the fault alarm the sounder can be silenced and the alarm
Led extinguished by the action of pressing and holding the button. The fault alarm can
also be set to self mute after a timeout period in order to preserve battery life. If this
happens the unit will give a short beep every 30 seconds thereafter.
An EPD conveys faults to the user by a number of displays, e.g.:
♦ Initialisation Error ( ---- on the LCD )
♦ Communications Error ( ==== on the LCD )
♦ Error Code ( Fxxx on the LCD )
♦ Blank Display
♦ Other faults (e.g. display lock-up, no heartbeat etc.)
___ ___ ___ ___
slow intermittent rate
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5.3 Internal Logging of Fault Conditions
5.3.1 EPD Status Faults Record
The EPD logs data to an internal data record in EEPROM, to indicate that faults have
occurred. These faults are as follows:
1. Event Logged. An event (dose alarm or a fault) has been logged
in the EPD’s event history store.
2. Communication Error. Communication with the EPD failed, typically the
unit was removed from the IR media prematurely.
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
5. Bad Sectors . The number of bad EPD secure store sectors.
6. Detector Test Fail. The EPD detector test was run and the number of
7. Detector Threshold Fail. The EPD detector thresholds failed to load
8. Radio Fail . Reserved for future use.
9. Other Fault. A fault occurred causing the EPD to reset.
10. Disabled. The EPD is ‘Off’ ( not calculating dose).
This data may be read and cleared via the IR communications link & EasyEPD2.
5.3.2 Event History store
The EPD logs up to 23 events in a non-volatile store, together with a time stamp. The
Event History store is accessible when the EPD is interrogated over the IR
communications link (e.g. by EasyEPD2). Alarm and fault events are recorded, see
Tables 4.1 and 5.2.
The store comprises a circular ‘buffer’, the latest event over-writing the oldest.
occurred.
There is a maximum of nine spare sectors.
counts received were less than required to pass
the test.
successfully
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Note: The date/time data field wraps round after 194 days of operation. After this
time previous event-associated day/date(s) cannot be considered as
accurate. In addition elapsed time during loss of power is not recorded.
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5.4 Blank LCD Display and Other Faults
It may also be possible for the EPD to fail without producing or displaying an error
code, or causing an alarm, for example due to failure of the micro-controller or digital
circuit. A list of such faults and the recommended course of action is given in the
table below.
Symptom Likely Cause Recommended Action
Blank Screen
Nothing displayed on the
LCD, not even ‘Heart
Beat’ indication
Nothing displayed after
battery is inserted/
replaced.
Static Screen
‘Heart Beat’ indication
not flashing
Faulty Button
Cannot mute alarm using
button
No response to button
Faulty Sounder
No audible alarm during
Battery Failure
Battery cap not
corrected seated
or battery out of
specification
♦ Attempt to communicate with the
EPD via the IR communications link
to prove diagnosis.
♦ Remove old and Insert new battery
and restart unit- see section 2.1.2.
♦ Communicate with the EPD via the
IR communications link to access
stored data.
♦ Remove and replace battery cap
(see Section 2.1.2).
♦ Use a recommended battery.
1 second timer error ♦ Attempt to communicate with the
EPD via the IR communications link.
♦ Replace battery and restart unit- see
section 2.1.2.
♦ Communicate with the EPD via the
IR communications link to access
stored data.
♦ If there is still no ‘Heart Beat’ contact
supplier.
Muting Disabled ♦ Communicate with EPD via the IR
communications link.
♦ Clear alarm conditions.
♦ Enable muting if required.
Hardware fault ♦ Communicate with the EPD via the
IR communications link to access
stored data.
♦ Contact supplier.
Hardware fault
♦ Contact supplier.
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Confidence Test
Sound fails to operate in
alarm condition
Faulty LED
No visual alarm during
Confidence Test
LED fails to operate in
alarm condition
Faulty Display
Missing or additional
segments on LCD
display
Sounder Disabled
♦ Enable sounder if required
Hardware fault
LED Disabled
♦ Contact supplier.
♦ Enable LED if required
Hardware fault ♦ Confirm fault by running a
CONFIDENCE TEST
♦ Contact supplier.
Table 5.1 - Blank LCD & other faults
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5.5 Initialisation Error ( LCD ---- )
A series of single dashes appearing on the LCD display indicates an initialisation
error following a reset or battery change:
Initialisation errors typically refer to corruptions to data in the EPD’s non volatile
memory (EEPROM). These are faults the user cannot usually repair. Follow the
procedures defined in section 8 to extract data and to recover normal operation
where possible .
5.6 Communications Error ( LCD ==== )
A series of triple dashes appearing on the LCD display indicates a communications
error:
This condition usually occurs when a data write operation fails to complete. The
typical cause is that the EPD unit is removed from the IR field before a critical write
operation has completed, for example an Issue of the EPD to a person.
The error ( which is accompanied by an audible alarm ) alerts the user that the EPD
is not in a valid operational state. However as described above, the cause is a user /
operational problem and not a fault in the EPD.
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An EPD will only raise this condition if it is first triggered by the system software, in
effect a message is pas sed to the EPD saying: “raise an alarm if the following write
operations don’t complete successfully within ‘N’ seconds.” If the condition does
occur then it is necessary to train the users not to remove the EPD from the IR field
until indicated ( i.e. by the system, through displays, Leds etc. ). However the EPD
communications software is tolerant of short duration loss of connection.
If the condition does occur it is normal for system software to clear the alarm and
LCD display automatically when the EPD is re-presented to the IR media. The
system software then checks the status of the EPD, completes any necessary data
write operations, advises the user what to do, and clears the alarm. The display then
returns to normal.
If the condition arises regularly then this may indicate a problem in the design of the
system software, i.e. the user interface.
If the user or system fails to clear the alarm in the way described above, then the
condition can easily be cleared using EasyEPD2.
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5.7 LCD Display Error Codes
Faults that exhibit a known condition are normally indicated on the EPD LCD as ‘F’
followed by a 3-digit error. The error code number is also logged in the Event History
store, with date/time data. As an example the following shows fault F095:
A list of EPD error codes is given in Table 5.2. They are divided into blocks
according to the software module that generates them.
Epd Action
This describes what the EPD does in addition to attempting to display the
fault and record the fault in the event history store.
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5.8 Recovery Procedures
5.8.1 Logging Faults / Extracting Data
All faults other than the communications error described in section 5.6 should be
logged using the standard Form in the Appendices. This form may be used to log
single or multiple faults. The completed form should be copied to the supplier of the
EPD ( Thermo Electron or other supplier / Distributor ).
If the unit is in operational use it is recommended that as much fault and operational
data as possible is extracted from the unit, via the LCD and using EasyEPD2. The
extent that this is possible will depend upon the nature of the fault. Note that for many
faults button/display operation and IR communications are unaffected. This includes
many Fxxx codes displayed on the LCD. Data should be extracted and logged as
follows:
1. Display fault code or indication ( Fxxx, ---- ).
2. Internal faults logged in the EPD Status Faults record.
3. Contents of internal Event History store.
4. Dose and peak dose-rate/time data ( if a spurious dose fault is suspected ).
5. Dose profile data ( if a spurious dose fault is suspected ).
Where possible the data should be obtained as screen dumps from EasyEPD2 and
attached to the completed Fault Log Form ( Appendix D ).
If a faulty unit is to be returned to Thermo Electron it must be returned in a fully
decontaminated and reasonably clean condition. The battery must be removed but
kept with the unit. The date of installation of the battery should be marked on the
battery.
5.8.2 Clearing faults
The steps required to clear a fault are as follows:
1. Extract data and fault information and complete a Fault Log Form,
Appendix D.
2. Identify the fault type in Tables 5.1 or 5.2 and take the recommended
action. This will range from resetting the unit (removing, then replacing
the battery), to returning the unit to the supplier ( Thermo Electron or
other Supplier or Distributor ).
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EPD/HB/40521/000
3. If the unit is to be restored to operational use, clear down all faults on
display and in the Fault Status Record, using EasyEPD2. This is to
ensure that any subsequent faults are detected.
Control Module
Code Text as displayed by
EasyEPD2
010 Control Module Error -
Critical
011 Control Module
Watchdog Timed Out
012 Control Module CRC
Failure
013 Control Module RAM
Failure
014 Control Module Stack
Overflow
015 Control Module Asic
Fault
016 Control Module
Unexpected Battery
Low
Note 1. This fault can occur when the battery cap is fitted if intermittent contact occurs. In this
event remove the battery cap, wait at least 10 seconds, then fit the battery cap again.
EPD
Action
Comms
only
Reset -ditto- S/W processing fault, possibly
Return to supplier. Supplier to re-initialise EPD
Halt Reset unit. Return
Reset -ditto- Only runs from self-test,
Halt Return to supplier. This test performs a read/write
Logged
in Event
Store
Recommended
Customer Action
Reset unit. Return
to supplier if recurs.
to supplier if recurs.
Return to supplier if
occurs regularly.
See Note 1 below.
Remarks
More than 2 consecutive resets.
Cause of reset to be identified.
micro-controller fault.
EEPROM and re-calibrate
Only runs from self-test,
typically every 15 minutes.
Other problems may well occur
before this time.
typically every 15 minutes.
Other problems may well occur
before this time.
test on the digital ASIC.
Unrecoverable — other knock
on errors may occur. Replace
ASIC
Texas chip has flagged bat low
or has reset and (Power
converter is off and no reset)
Comms Module
Code
020 Comms Module Error Reserved for future use
EPD TECHNICAL HANDBOOK Page 71
Text as displayed by
EasyEPD2
EPD
Action
Recommended
Customer Action
ISSUE 5
Remarks
EPD/HB/40521/000
Services Module
Code Text as displayed by
EasyEPD2
030 Service Module stCalData
CRC faulty
031 Service Module
stRateThres CRC faulty
032 Service Module
stDoseThres CRC faulty
033 Service Module
stDoseSummary CRC
faulty
034 Service Module stAdsData
CRC faulty
035 Service Module Seconds
Timer Array overflow
036 Service Module Fine Timer
Array overflow
037 Service Module Long Timer
Array overflow
EPD
Action
Reset unit. Return to
Reset unit. Return to
Reset unit. Return to
Reset unit. Return to
Reset unit. Return to
Reset Reset unit. Return to
Reset Reset unit. Return to
Reset Reset unit. Return to
Recommended
Customer Action
supplier if recurs.
supplier if recurs.
supplier if recurs.
supplier if recurs.
supplier if recurs.
supplier if recurs.
supplier if recurs.
supplier if recurs.
Remarks
This indicates a software
fault.
This indicates a software
fault.
This indicates a software
fault.
User I/F Module
Code Text as displayed by
EasyEPD2
040 User Interface Module Error Reserved for future use
Sounder Module
Code Text as displayed by
EasyEPD2
050 Sounder Module Error Reserved for future use
EPD
Action
EPD
Action
Recommended
Customer Action
Recommended
Customer Action
Remarks
Remarks
EPD TECHNICAL HANDBOOK Page 72
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EPD/HB/40521/000
EEPROM Module
Code Text as displayed by
EasyEPD2
060 EEPROM no more spare
sectors available
061 EEPROM bad sector,
requested sector number is
invalid
062 EEPROM bad sector
access table entry (number
is invalid)
063 EEPROM could not read
from the sector access
table area
064 EEPROM could not read
the next entry
065 EEPROM could not
reallocate data to a good
sector
066 EEPROM could not write
next entry
EPD
Action
Write
aband
oned.
Return to supplier This fault is unlikely to occur.
Return to supplier This fault is unlikely to occur,
Return to supplier Executes a Deferred Log
Return to supplier -ditto-
Return to supplier -ditto-
Return to supplier -ditto
Recommended
Customer Action
Return to supplier All 9 spare sectors have been
Remarks
used. This fault is unlikely to
occur in normal operation.
Tests have shown that the
EEPROMs are very resilient (
> 1 million bit toggles).
Sector Access Table is
corrupted or EEPROM read
failed
Fault with RECOVERED
option with the given fault
code but only if the EEPROM
fail bit is not set. If the
EEPROM fail bit is set the
fault is ignored to stop the
error store being flooded with
EEPROM fau lts.
Data Module
Code Text as displayed by
EasyEPD2
070 Data Module Error Reserved for future use
EPD TECHNICAL HANDBOOK Page 73
EPD
Action
Recommended
Customer Action
ISSUE 5
Remarks
EPD/HB/40521/000
Counts Module
Code Text as displayed by
EasyEPD2
081 Unexpected Texas chip
reset (Battery Low but no
Batt Low Status)
082 Consecutive Drop (more
than 45 seconds)
083 Counts not latched yet
no drop occurred
084 Counts Processing time
inconsistent
085 Count too large (HG or
SG > 300,000) or (FB or
BC > 26,000)
086 Detector threshold load
failed
087 A calibration value is out
of range
088 Abuse alarm (more than
45 consecutive seconds
of knocks)
EPD Action Recommended
Customer
Action
Reset unit.
Return to
supplier if
recurs.
No Longer Used
Reset into
comms
mode only —
counts
processing
disabled.
Reset Reset unit.
Reset - Ditto - This fault can occur by
Reset into
comms
mode only —
counts
processing
disabled.
Counts
processing
disabled
Nonecontinues
normal
processing
Return to
supplier
Return to
supplier if
recurs.
Reset unit.
Return to
supplier if
recurs.
Return to
supplier
Clear with
EasyEPD.
Return to
supplier if
recurs when
unit not
knocked.
Remarks
No Longer Used
ASIC or interface to ASIC
may be faulty.
The only reason to not-latch
the counts would be that a
knock has occurred.
Unlikely to occur unless
clock overflows. This is not
possible unless clock is
written with new value or
incremented at wrong rate.
inputting a very large number
of cou nts ( only
possible under test
conditions or severe
interference).
Texas chip or associated
circuits may be faulty.
Display will indicate dashes,
but error code can be
extracted from error log.
An error status bit is also
set.
This fault will be picked up
on power -up, writing cal.
factors or thresholds, or
switching from OFF to ON
mode.
Check knock detector
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EPD/HB/40521/000
Code Text as displayed by
EasyEPD2
090 Hard Gamma detector fail* None- continues
091 Soft Gamma detector fail* None- continues
092 Full Beta detector fail* None- continues
093 Beta Compensating
detector fail*
094 CRC error - Dose Alarm
Thresholds
095 CRC error - Rate Alarm
Thresholds
096 CRC error - ADS Data -ditto- -ditto- -ditto097 CRC error - Calibration
Factors
098 CRC error - Dose Data -ditto- -ditto- -ditto-
* only the first detector to fail is log ged
EPD Action Recommended
Customer
Action
Reset unit.
normal processing
normal processing
normal processing
None- continues
normal processing
Logs fault and
performs reset without
doing log first. This
means that good data
is read back from the
EEPROM. For the
ADS and Dose data,
the QF bits are also
set. This is done by
reading the data from
EEPROM, setting the
bit, calculating the
new checksum,
restoring the data to
EEPROM and then
doing a reset. The
correct values will
then be restored on
program restart.
-ditto- -ditto- -ditto-
-ditto- -ditto- -ditto-
Return to
supplier if
recurs.
-ditto- -ditto-
-ditto- -ditto-
-ditto- -ditto-
Reset unit.
Return to
supplier if
recurs.
Remarks
Only the first
detector to fail is
logged.
Indicates
corruption of data
in RAM. Up to 15
mins of dose
could be lost.
IRDA Module
Code Text as displayed by
EasyEPD2
100 IRDA Module Error Reserved for future use
Table 5.2 EPD Faults Logged to History Event Store.
EPD TECHNICAL HANDBOOK Page 75
EPD
Action
Recommended
Customer Action
ISSUE 5
Remarks
EPD/HB/40521/000
This page is intentionally blank
EPD TECHNICAL HANDBOOK Page 76
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SECTION 6
MAINTENANCE
This section describes the maintenance that may be required for the EPD.
Maintenance is limited to general cleaning, removing/replacing the EPD battery and
removing/replacing the EPD clip assembly. Limited maintenance can also be
carried to clear fault conditions and check the functionality of the EPD.
6.1 Calibration
The EPD is calibrated by a highly sophisticated automatic system consisting of
several radioactive sources. Calibration is performed during manufacture and is
expected to remain unchanged throughout the life of the EPD - provided the EPD
remains undamaged.
Thermo Electron’s normal policy is to supply EPDs with the calibration factors locked
to prevent their subsequent modification, other than by Thermo Electron. However
where expressly requested by customers in their purchase order, EPDs may be
supplied with the calibration factors in the unlocked sate. This is to enable such
customers to modify the calibration of these EPDs. In such cases the customers
attention is drawn to the following Disclaimer:
The EPDs within this shipment have been calibrated using the factors as defined on
the supplied Calibration Certificate. As the calibration is NOT LOCKED Thermo
Electron has no control over any subsequent adjustments made by the end user to
these factors. Thermo Electron can therefore not warrant the calibration of these
EPDs once they have left the factory. As such, Thermo Electron accepts no liability
for the accuracy of the radiological response of these EPDs.
EPD calibration may be checked using a Thermo Electron irradiator, or by exposure
to a known radiation field, in a manner approved by the appropriate regulating
authority or local rules. It is recommended that calibration is checked annually.
EPD TECHNICAL HANDBOOK Page 77
DISCLAIMER
ISSUE 5
EPD/HB/40521/000
A change in EPD calibration is usually indicative of a fault in the EPD and, due to the
complexity of achieving calibration over the full energy range, it is recommended that
any EPDs that fail calibration checks are returned to Thermo Electron for repair,
recalibration or replacement.
During calibration the calibration constants, and the threshold levels for each of the
four channels are set. The threshold levels determine the minimum pulse size that
will be considered a "count". The calibration constants ensure that the channels are
combined in the correct fashion to give correct dose readings.
Calibration Constants. Calibration constants convert the counts accumulated on
the four detector channels into dose equivalents. These constants are:
HGSens10
SGSens10
HGSens07
SGSens07
FBSens07
BCSens07
Detector Thresholds . Detector thresholds discriminate between radiation pulses
received by the EPDs detectors. These thresholds are set as course and fine values
measured as:
Hard Gamma (HG)
Soft Gamma (SG)
Full Beta (FB)
Beta Compensating (BC)
EPD calibration may be checked using a Thermo Electron irradiator, or by exposure
to a known radiation field, in a manner approved by the appropriate regulating
authority or local rules. It is recommended that calibration is checked annually.
A change in EPD calibration is usually indicative of a fault in the EPD and, due to the
complexity of achieving calibration over the full energy range, it is recommended that
any EPDs that fail calibration checks are returned to the manufacturer for repair or
replacement.
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6.2 The EPD Battery
The EPD can use either a Lithium Thionyl Chloride (LTC) 3.6 V battery or a standard
1.5 V AA battery (see Section 4.2). A battery change is within the scope of any
competent user. However, care must be taken when replacing the EPD battery (see
Section 6.2.3).
If the EPD is to be stored for a prolonged period of time the EPD battery should be
removed. There is no definitive battery installation period. The best philosophy to
adopt is: if in doubt - remove the battery.
6.2.1 Replacement Batteries
Replacement batteries must be suitable for installation into the EPD. On no account
must excessive force be used to insert the battery into its compartment. The
following are recommended replacement batteries:
Saft - Lithium 3.6 V (LS 14500)
Sonnenschien - Lithium 3.6 V (SL-760)
Duracell/Procell - Alkaline 1.5 V (MN 1500)
Other AA batteries may be suitable, however th e user is advised that:
1. The length of the battery including the battery anode (pip) should be in the
range of 49.0 mm to 51.0 mm.
2. The diameter of the battery should be in the range of 13.9 mm to
14.6 mm.
3. The diameter of the anode pip should be less than 5.7 mm. The battery
compartment has a feature to prevent reverse connection of the battery, and
an anode pip of more than 5.7mm diameter may fail to connect.
4. Battery life may differ from specification.
Detailed procedures for inserting/replac ing the EPD are given in Section 2.1.2.
6.2.2 Battery Leakage
Batteries that become expended should not be left in the EPD as they may leak,
especially LTC batteries. Batteries should also be removed from any EPD that is
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going to be left non-operational for any length of time to avoid the possibility that
leakage may occur and damage the EPD.
6.2.3 Lithium Thionyl Chloride Battery Warning
Lithium Thionyl Chloride (LTC) (Sulphurous Oxychloride, SOCl2) batteries are
potentially dangerous and can be harmful. The following warnings are to be
observed when inserting/replacing the EPD battery.
WARNING
Lithium Thionyl Chloride Batteries
1. Lithium Thionyl Chloride battery contents are potentially toxic, flammable and
explosive.
2. Lithium Thionyl Chloride batteries should not be:
♦ short circuited or charged under any circumstances.
♦ used in excess of +70°C and never exposed to temperatures in excess of
+100°C.
♦ opened, punctured, crushed or tampered with.
3. Batteries in storage should be kept in an isolated, dry, well ventilated cool
environment and kept out of direct sunlight. Storage temperatures should be
below +30°C.
4. Batteries are susceptible to fire and abuse. Some manufacturers provide
batteries with a safety vent, which allows a controlled release of electrolyte if
these conditions prevail. If the EPD has been damaged in a manner that could
affect the battery, care must be exercised during battery replacement. The
battery may have vented into the EPD case and caused the EPD to become
pressurized.
5. Electrolyte leakage can normally be detected by the smell of sulphur dioxide
and/or the presence of electrolyte solutes. If a leakage is suspected:
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(i) the battery should be removed from the EPD using protective
clothing, gloves, and goggles.
(ii) the battery should be placed in a self-sealing polythene bag (or
equivalent) and disposed of in the correct manner (see below).
(iii) Wash with copious amounts of water any areas that come into
contact with the electrolyte, especially the skin. Seek medical advice
if electrolyte comes in contact with the eyes.
6. Batteries must be disposed of in accordance with the manufacturer’s
recommendation and Local/National regulations.
7. If LTC batteries are to be transported by aircraft the batteries must be in their
correct packaging.
6.2.4 Replacing the EPD Battery
The EPD is fitted with either a security type (tamper-proof) battery cap or a coinrelease battery cap, depending on customer requirements. The security type battery
cap helps to prevent unauthorised removal of the cap and requires a special tool
(see Section 2, Figure 2.2). During fitment of the battery cap the EPD will begin its
initialisation sequence. This is intentional and performs the function of EPD start-up.
The procedure to replace/insert an EPD battery is described in Section 2.1.2. The
initialisation/start-up sequence is described in Section 2.1.3.
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6.3 EPD Clip Assembly
Depending on customer requirements, the EPD may (or may not) be fitted with a clip
assembly. The clip assembly comprises a lanyard plate and a spring clip, which
allows the user to attach the EPD to an outer garment (see Section 2.1.6).
The clip assembly is attached to the EPD by the lanyard plate. The lanyard plate
slots into a recess in the EPD case (see Figure 6.1). Retaining lugs secure the
lanyard plate in position.
Figure 6.1 - EPD Case Clip Assembly Recess
The lanyard plate may not be fitted with the spring clip (again depending on customer
requirements) (see Figure 6.3). This makes the unit more comfortable to wear with
the lanyard, when the clip is not required. If the EPD is shipped with the spring clip
fitted to the lanyard plate it should be considered as an integral item. Removal of the
clip from the lanyard plate is not recommended.
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Lanyard Plate
EPD/HB/40521/000
Figure 6.2 - EPD With Clip Assembly
6.3.1 Removing the EPD Lanyard Plate/Clip Assembly
To remove the lanyard plate/clip assembly, proceed as follows:
1. If the spring clip is fitted to the lanyard plate, open the jaws of the clip by
pushing downwards (see Figure 6.2) to give access to the lanyard plate. A
view of the lanyard plate (spring clip removed) is shown in Figure 6.3. Note
the tang on the lanyard plate (it is not necessary to remove the spring clip from
the lanyard plate in order to gain access to the tang).
Lanyard Plate
Tang
Button Press: (see Handbook)
PHOTON ENERGY: 0.015 - 10 MeV
STORED DOSE: 1usV - 16 Sv Hp(10)
Long - Next Menu or Mute Alarm
Short - Next Display or Lock-
on
Double - Start or Select
See handbook for
battery type & usage
SIEMENS ENVIRONMENTAL SYSTEMS LTD.UK.
(0.1 mrem - 1600 rem)
(Clip Assembly
Removed)
EPD TECHNICAL HANDBOOK Page 83
Figure 6.3 - EPD With Lanyard Plate
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2. Insert a screwdriver, with a blade width of 3 to 4 mm, under the lanyard plate
tang and apply downward leverage on the screwdriver (see Figure 6.4). At
the same time, push the lanyard plate towards the bottom of the EPD so as to
disengage the lanyard plate from the retaining lugs. Remove the lanyard
plate.
(Clip Assembly Removed For Clarity)
Figure 6.4 - Removing The EPD Lanyard Plate/Clip Assembly
6.3.2 Replacing The EPD Lanyard Plate/Clip Assembly
Set the lanyard plate into the recess on the rear of the EPD body. This will be found
to be much easier if the clip and lanyard plate is kept slightly open using a suitable
small separator. The plate should sit with its lugs in the lug recesses. Push the plate
towards the top of the EPD (LCD end), ensuring that the retaining lugs engage in
position in the clip assembly recess. Check that the lanyard plate is locked in
position (the plate remains in position when the assembly is pushed towards the
bottom of the EPD).
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6.4 Cleaning
The EPD is a sealed unit and has protection against dust and low pressure jets of
water from all directions. The unit will not withstand prolonged immersion under
pressure. Cleaning should be carried out if the unit requires general cleaning, if the
EPD battery has leaked or if the unit has come into contact with radioactive
contamination.
6.4.1 General Cleaning
The unit should be cleaned with warm soapy water. Use a neutral water-based
detergent, other detergents may damage or attack the EPD’s outer plastic coating.
A small brush should be used to clean any crevices in the case moulding. After
cleaning dry the EPD with a soft cloth. During cleaning, water may enter the alarm
sounder aperture. The sounder aperture is watertight, although water ingress may
deaden the alarm. Any water should be shaken or blown out of the sounder aperture
to restore the alarm noise level.
6.4.2 Radiological Cleaning
WARNING
DURING OPERATIONAL USE THE EPD MAY BECOME EXPOSED TO
RADIOACTIVE CONTAMINATION. THE EPD MUST BE SUBJECT TO ALL
RELEVANT DECONTAMINATION PROCEDURES LAID DOWN BY THE
RADIOLOGICAL PROTECTION AUTHORITY.
If radioactive deposits are present the unit should be decontaminated by carefully
wiping it over using a disposable cloth or tissue dampened with a detergent solution
and a small brush as described above, or alternatively by using a disposable 'sticky
wipe rag'. The unit should afterwards be checked with a sensitive radiation monitor
to ensure satisfactory decontamination has been achieved.
6.4.3 Cleaning after a Battery Leakage
Any leakage of the EPD battery must be treated with extreme caution. In most
instances battery leakage will be confined within the EPD battery compartment.
Minor leakage (light smearing) may be removed with a proprietary cotton bud
moistened with a water-based detergent. However, if doubt exists as to the extent of
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the leakage the EPD should be considered as unusable and the manufacturer
contacted for advice.
6.4.4 Periodic Cleaning
The EPD should be cleaned by wiping it over periodically with a cloth lightly
dampened with a solution of water and up to 5% of a neutral water-based detergent.
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APPENDIX A
RADIOLOGICAL SPECIFICATIONS
The following specifications quoted apply under standard conditions of 20°C.
Energy response
♦ Photon Hp(10) ±50% 15keV to 17keV (Ref. Cs-137)
±20% 17keV to 1.5MeV (Ref. Cs-137)
±30% 1.5MeV to 6MeV (Ref. Cs-137)
±50% 6MeV to 10MeV (Ref. Cs-137)
♦ Photon Hp(0.07) ±30% 20keV to 6MeV (Ref. Cs-137)
±50% 6MeV to 10MeV (Ref. Cs-137)
♦ Beta Hp(0.07) ±30% 250keV to 1.5MeV average beta energy (ref: Sr-90)
Angular response
♦ Hp(10) Cs-137 ±20% up to ±75°
♦ Hp(10) Am-241 ±50% up to ±75°
♦ Hp(0.07) Sr-90 ±30% up to ±55°
Accuracy
♦ Hp(10) Cs-137 ±10%
♦ Hp(0.07) Sr-90 ±20%
Dose rate linearity
♦ Hp(10) Cs-137 ±10% <0.5Sv/h
±20% 0.5Sv/h to 1Sv/h
±30% 1Sv/h to 2Sv/h
♦ Hp(0.07) Sr-90 ±20% <1Sv/h
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EPD/HB/40521/000
Typical EPD Mk2 Energy Response
1.4
1.2
Sr/Y
1
Kr
0.8
0.6
Response
0.4
0.2
0
10 100 1000 10000
Hp(10)
Hp(0.07)
Photon Energy (keV)
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APPENDIX B
ELECTROMAGNETIC COMPATIBILITY
Standard Test
The EPD was tested to the following specification with no failures:
Test Type Specification Test Frequency Range Level Notes
Radiated
Susceptibility EField
Radiated
Susceptibility EField
Radiated
Susceptibility HField
Electrostatic
Discharge
Radiated Electric
Field Emissions
Radiated
Susceptibility EField High Field
Radiated
Susceptibility EField High Field
Notes:
1. The limits are as Mil416D (Army) between 30Hz and 1kHz. Between 1kHz and
100kHz the limit is increased by 20 dB.
2. The units were tested up to the point of failure or to the maximum field attainable in
the test configuration.
Graphs follow:
Mil Std 416D RS103 10kHz – 40 GHz 200V/m
Def Stan 59-41 DRS02 14kHz – 18GHz 200V/m
Mil 416D RS101 30Hz – 100KHz See Chart 1 Note 1
EN61000-4-2 ESD N/A 8KV
EN 50081 -1 N/A 30MHz – 1 Ghz 30dB below
Limit
Spot Frequencies
CW
Spot Frequencies
CW with 1kHz 1
µS square wave
N/A 100kHz–40 Ghz See Chart 2 Note 2
N/A 500MHz–40 Ghz See Chart 3 Note 2
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Chart 1
10000
1000
100
Amps/Metre
10
1
10 100 1000 10000 100000
Frequency (Hz)
Chart 1. The tested Mk2 EPDs were not susceptible to H -field radiation below the above graph.
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