Thermo Electron EPD MK2 Technical Manual

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EPD/HB/40521/000

EPD MK2

Beta/Gamma Sensitive

Electronic Personal Dosemeter

Technical Manual

February 2004

REPRODUCTION IN WHOLE OR IN PART OF ALL MATERIAL IN THIS PUBLICATION, INCLUDING DRAWINGS AND DIAGRAMS, IS FORBIDDEN.

THIS INSTRUCTION MANUAL IS CONFIDENTIAL TO THERMO ELECTRON CORPORATION AND IS SUPPLIED FOR USE ONLY IN CONNECTION WITH THE OPERATION AND/OR MAINTENANCE OF THE EQUIPMENT TO WHICH IT RELATES, AS SUPPLIED BY THERMO ELECTRON CORPORATION. THE CONTENTS MUST NOT BE USED FOR OTHER PURPOSES, NOR DISCLOSED TO ANY THIRD PARTY, WITHOUT THE PRIOR WRITTEN CONSENT OF THERMO ELECTRON CORPORATION.

Thermo Electron Corporation

Sopers Lane, Poole, Dorset BH17 7ER. Englan d.

Tel:01202 782740 Fax: 01202 782056

ELECTRONIC PERSONAL DOSEMETER HANDBOOK

MANUFACTURERS DETAILS & ISSUE STATE

MANUFACTURERS DETAILS

Manufacturer's Address

Thermo Electron Corporation Environmental Instruments Division Radiation Measurement & Protection Sopers Lane Poole Dorset United Kingdom BH17 7ER

e-mail: service.epd.uk@thermo.com Tel. (01202) 782740

Fax. (01202) 782056

USA Sales Office

Thermo Electron Corporation Environmental Instruments Division Radiation Measurement & Protection 105C Hembree Park Drive Roswell Georgia 30076 U.S.A.

e-mail: epdsupport.rmp@thermo.com Tel. 770 521 4500

Fax. 770 521 4535

EPD/HB/40521/000

ISSUE STATE

Pages Issue Type Part ID File ID Change Ref

Front Sheet 5 ESERS EPD/HB/40521/000 HB40521_000_

cover_iss5

Balance 5 ESERS EPD/HB/40521/000 HB40521_000_

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GLOSSARY ...............................................................................................................................VII

EPD/HB/40521/000

CONTENTS

WARNINGS AND

SECTION 1...................................................................... ............................................................. 1

INTRODUCTION.......................................................................................................................... 1

1.1 G

1.2 EPD M

1.3 B

SECTION 2...................................................................... ............................................................. 5

GETTING STARTED ...................................................................................................................5

2.1 S

2.1.1

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

SECTION 3...................................................................... ...........................................................13

OPERATING INSTRUCTIONS.................................................................................................. 13

3.1 LCD D

3.2 A

3.2.1

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 D

3.5 D

3.5.1

3.5.2 Displaying Hp(0.07) Doses, Dose Rate and ADS User ID................................... 27

3.5.3 Displaying Total Dose...........................................................................................30

3.5.4 Starting/Stopping The Seconds Count Down Timer ............................................ 30

3.5.5 Turning the EPD off.............................................................................................. 31

3.5.6 Displaying Peaks (Rate High) .......................... ....................................................32

3.5.7 EPD Confidence Test........................................................................................... 32

3.5.8 Clearing Dose Display s ...................................................................................... .. 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

CAUTIONS....................................................................................................IX

ENERAL...................................................................................................................... 1

AJOR CHARACTERISTICS .................................................................................... 2

RIEF FUNCTIONAL DESCRIPTION .................................................................................. 3

ETTING-UP .................................................................................................................. 5

Unpacking The EPD............................................................................................... 6

ISPLAY AND BACKLIGHT ................................................................................... 13

UDIBLE AND VISIBLE ALARMS ................................................................................... 16

Alarm features ......................... ............................................................................. 16

ISPLAY LOCK-ON FACILITY ............................................................................... 24

ISPLAY OPTIONS AND BUTTON FUNCTIONS ................................................................ 26

Displaying Hp (10) Dose, Dose Rate and User ID...............................................26

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SECTION 4...................................................................... ...........................................................41

TECHNICAL DESCRIPTION..................................................................................................... 41

4.1 G

4.2 E

4.2.1

4.2.2 Battery Management ............................................................................................ 42

4.2.3 On / Off Operating Modes .................................................................................... 44

4.3 M

4.3.1

4.3.2 Brief Mechanical Description................................................................................45

4.4 ENVIRONMENTAL DESCRIPTION ................................................................................... 47

4.4.1

4.4.2 Brief Environmental Description........................................................................... 47

4.5 INFRA-RED INTERFACE ................................................................................................ 48

4.5.1

4.5.2 EPD Configuration via the IR Communications Links.......................................... 49

4.6 EPD INTERNAL PROCESSING & FACILITIES .................................................................. 51

4.6.1

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

4.6.6 Counts ..................................................................................................................54

4.6.7 Dose Quality Flags ............................................................................................... 55

4.6.8 Dose And Dose Rate Alarm Processing ..............................................................56

4.6.9 EPD Operating Status ..........................................................................................57

4.6.10 Dose Profile...................................................................................................... 60

4.6.11 Event History Store .......................................................................................... 61

ENERAL ................................................................................................................... 41

LECTRICAL DESCRIPTION.......................................................................................... 42

Electrical Characteristics...................................................................................... 42

ECHANICAL DESCRIPTION ......................................................................................... 45

Mechanical Characteristics And Dimensions....................................................... 45

Environmental Characteristics.............................................................................. 47

Communicating With The EPD............................................................................. 48

Memory Characteristics:....................................................................................... 51

Dose......................................................................................................................... 53

Dose Rate ................................................................................................................ 53

(i) Reset Count ........................................................................................................ 55

(ii) Knock Time Seconds ......................................................................................... 55

(iii) Dose Over-range............................................................................................... 55

(iv) Dose Rate Over-range......................................................................................56

(v) Counter Over-range........................................................................................... 56

(vi) Abuse Warning..................................................................................................56

(vii) CRC Failure...................................................................................................... 56

(viii) Low Voltage (EPD firmware version 11 and later)..........................................56

(ix) Detector Fault (EPD firmware version 11 and later)........................................ 56

EPD ‘Run’ and Off times .......................................................................................... 58

EPD State................................................................................................................. 58

Alarms ...................................................................................................................... 58

Faults........................................................................................................................ 58

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SECTION 5...................................................................... ...........................................................63

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CONTENTS

EPD FAULTS AND RECOVERY ACTIONS

5.1 O

5.2 V

5.3 I

5.4 BLANK LCD DISPLAY AND OTHER FAULTS .................................................................. 67

5.5 I

5.6 C

5.7 LCD D

5.8 R

SECTION 6...................................................................... ...........................................................79

MAINTENANCE

6.1 C

6.2 T

6.3 EPD CLIP ASSEMBLY ................................................................................................. 86

6.4 CLEANING................................................................................................................... 89

APPENDIX A ............................................................................................................................. 91

VERVIEW .................................................................................................................. 63

ISUAL AND AUDIBLE FAULT INDICATION ..................................................................... 64

NTERNAL LOGGING OF FAULT CONDITIONS.................................................................. 65

5.3.1

5.3.2 Event History store............................................................................................... 65

5.3.3 Dose Quality Factors............................................................................................ 66

5.8.1

5.8.2 Clearing faults.......................... ............................................................................. 72

6.2.1

6.2.2 Battery Leakage ................................................................................................... 82

6.2.3 Lithium Thionyl Chloride Battery Warning............................................................82

6.2.4 Replacing the EPD Battery................................................................................... 84

6.3.1

6.3.2 Replacing The EPD Lanyard Plate/Clip Assembly ............................................... 88

6.4.1

6.4.2 Radiological Cleaning....... .................................................................................... 89

6.4.3 Cleaning after a Battery Leakage......................................................................... 89

6.4.4 Periodic Cleaning ...................................... .............................................. .............90

EPD Status Faults Record....................................................................................65

NITIALISATION ERROR ( LCD ---- ) ............................................................................. 69

OMMUNICATIONS ERROR ( LCD ≡≡≡≡ ) .................................................................... 69

ISPLAY ERROR CODES ..................................................................................... 71

ECOVERY PROCEDURES ............................................................................................ 72

Logging Faults / Extracting Data .......................................................................... 72

......................................................................................................................... 79

ALIBRATION .............................................................................................................. 79

HE EPD BATTERY..................................................................................................... 82

Replacement Batteries .........................................................................................82

Removing the EPD Lanyard Plate/Clip Assembly................................................ 87

General Cleaning.................................................................................................. 89

............................................................................. 63

RADIOLOGICAL SPECIFICATIONS........................................................................................ 91

APPENDIX B ............................................................................................................................. 93

ELECTROMAGNETIC COMPATIBILITY.................................................................................. 93

APPENDIX C ............................................................................................................................. 97

SUMMARY OF GENERAL PHYSICAL & FUNCTIONAL CHARACTERISTICS.................. 97

APPENDIX D ........................................................................................................................... 102

EPD FAULT LOG FORM......................................................................................................... 103

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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 threshold s 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 u nit of dose HEX Hexadecimal

EPD LCD nomenclature for personal dose (Hp(10))

EPD LCD nomenclature for personal dose (Hp(0.07))

/h EPD LCD nomenclature for dose rate (Hp(10)/h)

/h EPD LCD nomenclature for dose rate (Hp(0.07)/h)

Hp(10) Personal dose equiva lent at a dept h of 10mm of tissue (‘penetr ating’,

‘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 Radia tion 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 (Sulphuro us O xychlor i de, SOCl 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)

PTB The Physikalisch-Technische Bundesanstalt, Braunschweig

and Berlin. The national institute of natural and engineering sciences and the highest technical authority for metrology and physical safety engineering of the Federal Republic of Germany.

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 Inter f er en ce 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 AND CAUTIONS

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* (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, SOCL

Lithium Thionyl Chloride Batteries

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 m anner that could affect the bat tery, care must be exercised during battery removal. The bat tery may have vented into the EPD case and caused the EPD to become pressurised.

EPD Battery Cap

Take care when removing the EPD battery cap, the battery cap may spring free with unexpected force.

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ELECTRONIC PERSONAL DOSEMETER HANDBOOK

SECTION 1

INTRODUCTION

This handbook is for the Thermo Electron Corporation Electronic Personal Dosemeter (EPD), Beat/Gamma variant, Mks 2.0, 2.1, 2.2 & 2.3. The EPD Mk2 family is lighter and slimmer than the original Mk1 EPD and has new microcircuitry, case design and software. The Mk2 EPDs also have a number of enhanced dosimetry features and user functions. To simplify nomenclature the term EPD has been used througho ut this handbook and should be read to signify the EPD Mk2 Beta/Gamma dosemeter.

1.1 General

The EPD is a personal radiation monitor that detects and measures beta and gamma radiation. Radiation that is dete cted 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 radiation. 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 interfa ce comprising an LCD display and butt on. Each of the above functions is described in detail in this handbook.

The EPD has a rich feature s et which can be conf igured to the use rs requirem ents over the IR communication link using suitable software such as EasyEPD2. These configuration options are e xplained in th is handbook but the user is also referred to the EasyEPD2 User Manual which describes the parameters in more detail and how they are accessed. Note that a few parameters are accessible only by the manufacturer and must be deter mined before delivery takes place (c alibration lock and PTB Approval are examples). These manufacturer settings may constrain what the end user can configure in the EPD, see section 4.5.2.

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1.2 EPD Major Characteristics

Major Characteristics relating to the EPD are listed in Table 1.1.

Table 1.1 - EPD Major Characteristics

Item Characteristic

Power One AA battery, either a standard Alkaline (1.5 V) battery

or high energy Lithium Thionyl Chloride (LTC) (3.6 V). Weight 95 gms (including LTC battery and clip). Dimensions 86 x 62 x 18.5 mm (excluding clip). Alarm sounder 98 - 101 dB on loud 4kHz setting.

Quiet and 2 kHz settings available.

Dose-chirp function on Hp(10) dose.

The EPD also has the following major features:

♦

Improved immunity to radio frequency inter ference (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 functio ns. Extended systems integration facilities.

♦ Count down timer and alarm.

Appendix C is a

summary of the general physical & functional characteristics of the EPD.

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1.3 Brief Functional Description

The EPD is a highly sophisticated device sensitive to gamma and X-rays (photons), and beta radiation ( en er ge tic electrons) in the following energy range:

gamma, X-rays : 15 keV to 10 MeV

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INTRODUCTION

Beta radiation:

250 keV to 1.5 MeV (mean energy)

A full list of radiological chara c te r ist ics and specifications can be found in A ppe nd ix A to this Handbook.

Radiation detected by the three silicon diode detectors is combined to give the following dose equivalents (as defined by ICRU Documen t 47 ):

(i) Hp(10) pe rs onal dose eq uivalent at a dep t h of 10mm of tissue (‘pen etr atin g’,

‘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, a re 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 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 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 also produces a range of Access Control Syst ems f or use with the EPD.

Dose is accumulated separately in the EPD in three stor es:

ADS Dose

periods, for example the (and reset after each ), whilst the

. The use of several stores allows dose to be recorded over dif fering

Dose

store may be used for each job or task p erformed

Total Dose

records the total or aggregate do se

Dose, Total Dose

and

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 t o:

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♦

Removing/replacing the EPD battery,

♦ Removing/replacing the EPD clip assembly,

♦

Clearing fault conditions (where possible),

♦ Checking the functionality and calibr ation of the EPD,

♦

Note:

Keeping the unit clean.

1. This manual deals with Sievert s ( Sv) t hr ougho ut . To conver t to re m multip ly

all values by 100.

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SECTION 2

GETTING STARTED

This section describes the general procedur es 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,

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GETTING STARTED

5. Performing a confidence test. A general view of the EPD is shown in Figure 2.1. E xternal feat ures are de scribed

in Table 2.1.

Thermo

Figure 2.1 - External View Of The EPD

Feature Description

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Battery Compartment Houses an Alkaline AA battery (1.5 V) or a Lithium

Infra-red Interface Infra-red communications interface to th e EPD. Button User interface for EPD control, alarm

Sounder Provides an audible indication of an EPD alarm. Beta Window Allows beta particles to pass through the case to the

LCD Display Displays EPD parameters and/or functionality as

Alarm LED Provides a visual indication of an EPD alarm. Clip Assembly Provides a means of attaching the EPD to clothing, or

Thionyl Chloride (LTC) AA battery (3.6 V).

acknowledgement and LCD display selection.

Beta detector.

selected by the button.

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.

* Sulphurous Oxychloride, SOCl2)

WARNING

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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 interna l circ u it s of the EPD to power-down).

The EPD is fitted with either a security-t ype (tamper-proof) battery cap or a coinrelease battery cap, dep ending on customer requirements (see Figure 2.2). The security-type battery cap restricts unauthorised removal of the cap and req uires a special tool. The coin type battery cap should be rotated using a small coin circa 20 mm diameter and 2 mm thick.

EPD/HB/40521/000

GETTING STARTED

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Figure 2.2 - Battery Cap Types and Special Tool

The battery cap also provides the retu r n path for the EPD’s power supply. Therefore, during fitment of either type of battery cap the EPD will begin its startup 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 att emp t 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) b elow.

(ii) If the battery cap is of the

tool into the two conical recesses in the battery cap. If the battery cap is of

coin type

the

(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 alread y fitted, the cap will normally release from the case under the action of the battery ca p comp r ession spr in g.

Note: Do not attempt to rotate the cap beyond the design point

security type

, locate the two pips of the special

, locate the coin in the groove in the battery cap.

(approximately 85 degrees) or beyond the point where the resistance of the end-stop is f elt.

Figure 2.3 - Battery Cap Removal

(iv) Remove the existing battery (if fitted). Ins ert a new ( or r eplacem ent ) batt ery

into the battery compartment as shown in Figure 2.4.

Note

: The battery must be inserted anode (

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ELECTRONIC PERSONAL DOSEMETER HANDBOOK

Figure 2.4 - Inserting The EPD Battery

EPD/HB/40521/000

GETTING STARTED

(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 (

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 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 sequenc e. The start-up sequence is as follows:

1. ‘8888’ is shown on the display for approximately t hr ee seco nds;

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.);

3. confidence test sequence, see section 2.1.4 below.

) electrode contact

°, to its end-stop. Rotate the

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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 bat tery. If problems persist, refer to section 5.

2.1.4 EPD Confidence Test

The EPD has a built-in confidence test facility. This runs automatically at startup following battery change. When enabled, this test can also 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 butto n.

The confidence test sequence is as follows. This test seq uence 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 func tiona l ( 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 d isappear 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 separate, configuration for Approved Dosimetry Service (ADS). The User Name and numerical ID can only be configured via the IR communications link.

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ELECTRONIC PERSONAL DOSEMETER HANDBOOK

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 but ton 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 prot ective 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.

EPD/HB/40521/000

GETTING STARTED

Thermo

Figure 2.5 - Wearing An 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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GETTING STARTED

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.

WARNING

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ELECTRONIC PERSONAL DOSEMETER HANDBOOK

EPD/HB/40521/000

OPERATING INSTRUCTIONS

SECTION 3

OPERATING INSTRUCTIONS

This section explains the essential functions perf ormed 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 ar e activated in this way temporarily during the start-up sequence, and during user initiated

Test

, (see Section 3.5.7). On completion of the start -up sequence o r

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 s hown in Figure 3.4. Default settings and other display controls are changed using a suitable IR communications link and software (e.g. display can be configured to display values in either Sieverts or r e m s.

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 displays available may lead to confusion and Thermo has therefore provided a facility for unwanted or unnecessa r y disp la ys to be disab led.

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 backlight effect is not apparent and the user may assume that a button press operation has somehow been ‘lost’.

EasyEPD2

. However for many users the sheer number of

EasyEPD2

Confidence Confidence

). For example, the

Thermo

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OPERATING INSTRUCTIONS

♦

The backlight activation causes a temporary alarm muting effect, see section

3.2.5.

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EPD/HB/40521/000

OPERATING INSTRUCTIONS

Thermo

Figure 3.2 - LCD Display Segments

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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. Ala rms 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.

Figure 3.1 - Alarm LED And Sounder

It is possible to disable the sounder and/or LED so that only one or neither will activate, but alarm flags on the LCD r emain 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 an d mute th e sounder. It is po ssible to disa ble the mut e function, via the EPD IR communications link (see section 3.2. 5) .

Note that certain operations and events will a utomatically 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.

Communication over the IrDA link 1 second or more, depending upon the

application.

Communications over the

Less than a second.

teledosimetry link. Backlight activated (from the button). Default display timeout ( typically 10

seconds ), during which the backlight is on.

Battery test ( typically every 15

Less than 1 second.

minutes ).

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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 set in increment s 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 the n so cu r ta iled.

EPD/HB/40521/000

OPERATING INSTRUCTIONS

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

I nt e rmittent Double Beep Fast

to 17 minutes

Table 3.1 - Alarm Configuration Options

Table 3.2 - Alarm Sounds

Note

: High Frequency = 4 kHz (approximately)

Low Frequency = 2 kHz (approximately) * To obtain the loudest alarm output it is necessary to conf ig ur e the

alarm to Loud and High frequency.

Thermo

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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 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 on e alarm condition to preva il 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 p r iority 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 and the following points should be not ed :

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.

only

3. If the LED (or sounder)

is disabled then the LED (or sounder) out put 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.

In general therefore the higher priori ty alar ms 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.

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EPD/HB/40521/000

OPERATING INSTRUCTIONS

Priority

1 EPD Failure Alarm. Intermittent Single Slow Tone

2 Over-range Alarm. Continuous Dual Fast Tone

3 Hp (10) Dose Alarm

4 Hp (0.07) Dose

5 Hp (10) Dose Alarm

6 Hp (10)/h Dose

7 Hp (0.07)/h Dose

8 Hp (10)/h Dose

Alarm/Event

(2)

Alarm

(1)

Rate Alarm (2)

Rate Alarm

Rate Alarm (1)

__ __ __ __

_-_-_-_-_-_

Continuous Single Tone ____________

Intermittent Single Fast Tone _ _ _ _ _ _ Intermittent Single Fast Tone _ _ _ _ _ _

Alarm Tone

Frequency Volume

High Loud

High/Low 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

__ __ __ __

Table 3.3 - Default Alarm Tones

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Low Quiet

High Loud

Low Quiet

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OPERATING INSTRUCTIONS

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 ap propriate alarm flag on the LCD will be displayed. Note that it is dose and not total dos e th at is compared with the threshold.

The alarm may be muted by pressing and holding the butt on, unless alarm mute (user silence) is inhibited.

The four most significant digits of t he 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 alar m 'On' thresho lds 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).

EPD/HB/40521/000

OPERATING INSTRUCTIONS

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 over-range 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 audible and

Led alarm 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. For software version 11 and later EPDs the over-range indication on the

LCD may be configured to operate in either of two ways. By default the LCD will alternate between the current display selection and a blank display. The alternative configuration causes the LCD to alternate between the current display selection and 9999.

Thermo

4. The 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 fa cilities being enabled f or the alarm. The appropriate LCD alarm flag is always activated. The user can silence ( mute ) the alarm by pressing and holding the button, provide d 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 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.

the display backlight is enabled a short press of the button turns the

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OPERATING INSTRUCTIONS

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 n umber of menus, each having a toplevel display. Menus are chan ged by holding down the butt on (Long Press) . This navigates the user down the left han d side of Figure 3.4. Once the desired men u 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 facility is available in

EasyEPD2

of EPD units. Some displays allow the user to change the status or ope ration 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.

EasyEPD2

to enable the speedy configuration of a number

EPD/HB/40521/000

software package. A batch writ e

Thermo

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OPERATING INSTRUCTIONS

3.4 LCD Display Lock-on Facility

Any new display selected using the button remains visible for a set period of time, (Thermo 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 pres s the but ton. The dis play will move on to th e 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 above. In this instance the lock-on facility is available when the colon disappears and, again, is just before the display times out. To accept the lock-on facility, press the button when th e colon disappears. If t he lock-on facility is not r equired, allow the selected display to time-out.

. This only occurs for the count-down timer display

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Blank

Timer

Peaks

Test

Clear

larm ON

larm Off

Sound

Settings

Display:0

HP10

HP07

t0t

5E C5

OFF

r hi

tE5t

CLr

d AL r on

roFF

bEEP

Sub-Displays

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

larm ON

1st H10

Dose Rate

larm 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

2nd H10

Dose Rate

larm

Off

Chirp Dose

djustment

User ID digits

5,6,7,8

DS User ID

digits 1,2,3,4

Dose Alarm

H07 Dose

Rate Alarm

H07 Dose

Rate Alarm

Internal

Counters

Display* * = Lock-on

Top-Level Display

Button Operation: Long- Next Menu or Mute Alarm

H10 Doses

H07 Doses

Total Dos es

Countdown

Power Saving

(Rate High)

Dose Alarm

Thresholds

Dose Rate

Thresholds

(Rate On)

Dose Rate

Thresholds (Rate Off)

EPD/HB/40521/000

OPERATING INSTRUCTIONS

1,2,3,4

digits 9,10,11,12

User ID digits

9,10,11,12

DS User ID

User ID digits

DS User ID

digits 5,6,7,8

H07

Off

Figure 3.4 - LCD Display Selections

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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 acces s to any (or none) of the displays, dep ending on how the EPD has been configured. To call up a top-level display, press and hold the button until the relevant t op-level display appears. Any sub-displays are selected either by short-pr essing, or double- pressing, th e button with in 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 t o display the current dose. This dose parameter is used for tactical dose monitoring (e.g. per task etc.).

Display Range: 0

µSv to >16Sv (auto ranging)

Note

: Over-range (> 1.0 Sv) is indicated with a flashing LCD display (see section

3.2.4).

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.

Display Range: 0

Sv/h to >4Sv/h (auto ranging)

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Note

: Over-range (> 1.0 Sv/h) is indicated with a flashing LCD display, see

section 3.2.4. This condition is latched to war n the use r th at the dos e value may be inaccurate.

User ID Digits

Short-press the button a gain to d isplay the user id entity numbe r (User ID). This is a 12-digit number that is shown on thre e separate displays - the High 4 digits, the Middle 4 digits and the Low 4 digits. Short-press t he 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. Fo r example, a User ID = 9012 will be shown on the LCD display as follows:

(First Display) (Second Display) (Third Display)

EPD/HB/40521/000

OPERATING INSTRUCTIONS

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).

For software version 11 and later the first 12 characters of t he wearer name may be displayed on the EPD LCD in place of the wearer ID. The character representation on a seven segment display is necessarily limited, see table in Appendix C.

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 unt il this toplevel display appears:

Three sub-displays are available (in the following sub-display or de r ) :

♦

Hp(0.07) Dose

Thermo

♦ Hp(0.07)/h Dose Rate

♦

ADS User ID Digits

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Hp(0.07) 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: 0

µSv to >16Sv (auto ranging).

Note: Over-range (> 1.0 Sv) is indicated with a flashing LCD display, see section

3.2.4.

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: 0

µSv/h to >4.0Sv/h (auto ranging).

Note:

Over-range (> 1.0 Sv/h) is indicated with a flashing LCD display, see

section 3.2.4. 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, calle d Approved Dosimetry Ser vice (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 disp lay 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)

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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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Count-down Time MM:SS Reset (rSt)

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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 th e 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, o r 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 t he display reverts to th e default display after the display t imeout period. Ho wever it is usefu l to ‘lock on’ to this display as described in section 3.4.

EPD/HB/40521/000

OPERATING INSTRUCTIONS

Stopping the Timer

To stop the timer double-press the button again. The d igits will stop decr ea sin g.

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 confir m the reset (the display will show the reset time at its reset value). The timer may now be star t ed as described above.

3.5.5 Turning the EPD off

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.

Thermo

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Assuming that the display shows On, double-press the button. The display will change to “OFF” (flashing). Double- press the button again to confir m the request . The display will change to the word “OFF” (not f lashing), conf irming that the unit is in OFF mode and not measuring radiation.

To return to operating mode pre ss and hold the button. The display will rever t 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 t hat 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

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

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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 tim e during oper ational use as a con fidence check that the EPD is functioning correctly. Throughout the confidence test the heart-beat (activity) indicator flashes onc e 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 (1 to 2 ms approximately).

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 ar e f un c tion al (se e Figu r e 3 .2).

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OPERATING INSTRUCTIONS

2. The alarm will sound and the LED will flash for appro ximately 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 ap proximately 6 seconds. This indicates that the LCD segments can be turned off, and that the tone frequencies are fun c tion al.

4. The all-segme nt 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 unsuccessfu l a le tter ‘F’ followed by th ree digit s is displayed . Note the failure codes and refer to Section 5 (Failure Modes and Fault Diagnosis).

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3.5.8 Cleari ng Dose Displays

To clear dose displays, press and hold the button until this toplevel display appears:

Only one sub-display is available

♦

This mode is used to clear the Hp(10) and Hp(0. 07) doses.

Note

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 req uest. The display will change to 0000 and return to the default display. The Hp(10) and Hp( 0. 07 ) dose s have now been cleared.

Clr?

: The total doses are not cleared.

3.5.9 Displaying/Setting Dose Alarm Thresholds

To display and/or set dose alarm thresholds, press and hold the button until this top-level display appears:

Three sub-displays are available (in the following sub-display or de r ) :

♦

♦ 2

♦

1st Hp(10) Dose Alarm

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 t he threshold if the default is set to ‘not adj ustable’. These default settings can only be set via the IR communications link.

There are two Hp(10) alarm thresholds and a single Hp(0.07) alarm threshold that can be displayed and modified. The 2

Hp(10) dose alarm has the higher pr iority

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and should always be set to a higher value than the 1st Hp(10) alarm. The accumulated dose alarm threshold s can be set using the button as follows:

& 2nd Hp(10), Hp(0.07): 10µSv, 50µSv, 100µSv, 500µSv, 1mSv, 5mSv,

10mSv, 50mSv, 100mSv, 500mSv, 1.0Sv.

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Example of 1

Hp(10) Dose alarm threshold display set at a default value of 500

Sv:

Other values for the dose alarm thresholds may be set via the IR communications link.

Changing The Dose Alarm Thresholds

To change the 1

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: 10

µSv to 1Sv.

Pressing the button will increase the alarm threshold in the following steps: 10

Sv, 100µSv, 500µSv, 1mSv, 5mSv, 10mSv, 50mSv, 100m Sv, 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 butt on is not pressed, after default timeout the display will return to the dose alarm threshold that was being set-up. Again, if the button is not p r essed, the display will return to t h e default screen after a further time-out period.

µSv,

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OPERATING INSTRUCTIONS

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 or de r ) :

♦ 1

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:

♦

♦ 2

♦

1st Hp(10)/h Dose Rate Alarm OFF

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 a larm 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 2 higher priority and should always be set to a higher value than the 1

Hp(10)/h dose alarm has the

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 thresholds 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 t he b ut t o n as f ollows: 10

µSv/h, 50µSv/h, 100µSv/h, 500µSv/h, 1mSv/h, 5mSv/h, 10mSv/h,

50mSv/h, 100mSv/h, 500mSv/h, 1.0Sv/h

Other values for the dose rate alarm thresholds may be set via the IR communications link.

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OPERATING INSTRUCTIONS

Note: To avoid false alarms due to count ing statistics it is recommended that the

Hp(0.07)/h dose rate alarm is not set to less than 100

Example 1 alarm threshold display set at a default value of 500

'On' and 'Off' alarm thresho lds allow hysteresis for dose rate alarms, see section

3.5.1. If hysteresis is not to be used the ‘O n’ and ‘Off’ thresholds should be set to the same value.

Changing the Dose Rate Alarm Thresholds (ON and OFF)

To change the 1 rate 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: 10

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, 1.0 Sv/h. When the required threshold is reached doublepressing the button to confirm the value an d t he flashing display will stop.

Hp(10)/h dose rate on

Sv/h:

(10)/h dose

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Sv/h

Sv/h to 1Sv/h

Thermo

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 no t pressed, after default timeout the display will return t o dose alarm thres hold 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’

2. If an attempt is made to set the ‘On’ threshold below the ‘Off’ threshold the

3. If an attempt is made to set the ‘Off’ threshold above the ‘On’ threshold the

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 or de r ) :

♦ Button Beep Enable/Disab le

threshold.

‘Off’ threshold will be set automatically to the same value as the ‘On’ threshold.

♦

Note

Dose Chirp Adjustment Internal Counters Display

: 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.

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

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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 (d eep) dose. This increment can be set between 0.01

and 100

µSv, or disabled by setting the increment to 0.

Short-press the button to display the current dose per chirp:

An increment set to

opposite. W

Sv/chirp and a dose rate of 10mSv/h

ith a chirp sensitivity of

1µSv is shown

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 ).

Pressing the button will increase the dose per chirp in the following increments:

0.0

Sv, 0.01µSv, 0.05µSv, 0.1µSv, 0.5µSv, 1.0µSv, 5µSv, 10µSv, 50µSv,

100

Sv. When the required sensitivity is reached “double-pressing” the button will

confirm the value and the flashing disp lay will stop.

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µSv

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If you start to change th e sensitivity, and change your mind, the option can be aborted. Short-press the button until the following is displayed (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 displayed.

If the “ESC” screen is displayed and the button is not pressed, after default timeout the display will return to dose chirp adjustment display. Again, if t he 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) counts respectively. This display is intended for test purposes and may be useful for identification of faults or operational pro blems.

Sv is

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SECTION 4

TECHNICAL DESCRIPTION

This section provides a technical description of the EPD and contains a summar y of the EPD’s radiological features tog ether with a summ ar y of th e EPD’s elec tr ical, 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

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TECHNICAL DESCRIPTION

♦

♦ Direct readout of personal dose equivalents Hp(10)

♦ Neutron response <2%

♦

♦ Resolution for dose display 1µSv (0.1mrem) at levels up to 10mSv (1 rem)

♦

Multiple PIN diode detectors 4 channel parametric algorithm processing

(penetrating/deep/whole body) and Hp(0.07) (superficial/shallow/skin )

Meets relevant parts of BS-EN-ISO61526 for dose equivalent monitors (unless otherwise specified)

Dose display and storage 0µSv to >16Sv (0.0 mr em to > 1600 rem) auto ranging

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 (10 Dose rate peak store 0µSv/h to >4Sv/h resolution 1µSv/h

Sv/h for Hp(0.07)/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 <5 hours total during battery life.

or:

One standard AA Alkaline battery (1.5 V), giving typically

55 days continuous operation at an ave rage dose <5 with the alarm sounding <2 hours total during batt ery life.

Confidence Test: Activated on start-up and by the button when the

CONFIDENCE TEST mode is called-up (see Section

3.5.7).

Sv/h with the alarm sounding <5

Sv/h

Detector Test: Performed during the start-up sequence and as a

background test, and under demand via the IR interface . Normal dose processing is inhibite d during detector test for a period of 1 to 2 ms.

Battery Test: Configurable time interval between 1 to 60 minutes. (15 minutes recommended).

Alarm sounder : 98 dB(A) to 101 dB(A) at 20 cm (4kHz loud mode) 80 dB(A) to 90 dB(A) at 20cm (4kHz quiet mode).

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, SOCL battery or a standard 1.5V AA Alkaline type ba ttery.

The EPD software runs an internal battery condition test at regular intervals (between 1 and 60 minutes). Th is time interval is factory preset to 15 minute s and should not be adjusted except following consultation with Ther m o Ele ctron.

EPDs prior to software version 11:

)

If a 1.5V Alkaline battery is inst alled the EPD automatically switches-in a step- up converter to maintain the 3.6V o perating voltage. The step-up converter is also switched in as the LTC battery runs down. However, the EPD will not start up if it

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is fitted with a LTC battery that has been discharged sufficiently to require the step-up converter to opera t e .

Operationally, as the voltage from either battery type falls, a series of preset voltage thresholds operate as follows:

(i) The in ternal step-up converter is switched in to ma intain the voltage at the

EPD’s operating level.

(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 selected for LTC or alkaline batteries.

(iii) As the battery voltage under load finally falls below tolerance the EPD

resets (blank display). In some cases the EPD may reset repeatedly, giving rise to a quiet ticking sound. The EPD battery must be rep lac ed.

EPDs from software version 11 onwards:

These EPDs have the step-up converter permanently activated to maintain the required circuit operating voltage as either the Lithium or the Alkaline battery voltage falls. The EPD makes the following information available over the IR comms link:

•

Type of battery current ly fitted: Low volts (Alka line) or high v oltage (Lith ium Thionyl Chloride)

•

The current battery voltage (measured at the last battery load test – normally every 15 minutes)

•

The current regulated circuit voltage (measured within the last 14 seconds)

•

The battery voltage threshold at which the battery low warning is raised for low voltage (Alkaline battery) *

•

The battery voltage threshold at which the battery low warning is raised for high voltage (Lithium battery)*

* These thresholds should not nor mally require adjustment and any adjustment considered should first be agreed with Ther mo Ele ctron.

The battery low alarm and LCD segment are activated when the battery voltage falls below the appropriate battery low threshold. The EPD will continue to run normally thereafter for a period of at least 10 hours, though this may be shortened by continuous audible alarm outpu t. When the EPD is no longer able to contin ue correct processing it enters a hardware reset state in which intermittent audible alarms are output until such time as the battery nears complete discharge state. This may continue for several minutes or longer. As the sound is initiated by the hardware it cannot be muted by pressing the button, but only by removing the battery.

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TECHNICAL DESCRIPTION

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TECHNICAL DESCRIPTION

Additional information and warnings relating to the EPD battery are given in Section 6.2.

4.2.3 On / Off Operating Modes

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 of f - 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 co ndition (i.e. fully operational). The EPD does not measure radiation when it is OFF.

Alternative OFF Display EPDs of software version 11 and later may be configured to display a 4 digit

Hexadecimal value instead of the OFF display. The 4 digit hex value may be written using suitable software, e.g. EasyEPD2. This facility is to provide customers with the option of having the EPD display the Calibration due date when the EPD is Off. So for example, 2512 could mean calibrate on 25 December.

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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.

EPD/HB/40521/000

TECHNICAL DESCRIPTION

4.3.2 Brief Mechanical Desc ri pt ion

The EPD is of semi-modular construction and compr ises an inner co nduct ive 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 to gether 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 assemb ly. The outer case an d lid are designed not come apart.

The complete assembly is engineered to house functional and operation components (e.g. EPD battery, LCD displa y, button, alarm LED, alarm sounder, IR communications link and beta window (see Fig ure 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 t he EPD bat tery, bat tery 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).

EPD/HB/40521/000

TECHNICAL DESCRIPTION

4.4.2 Brief Environm ent al De scription

The EPD is designed for use in the following environments:

♦ Office and Laboratory environme nt ,

♦

Industrial environments, Hospitals Military environments (including dockyards and shipping - but excluding

exposure to salt water and extremes in military en vir o nment).

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TECHNICAL DESCRIPTION

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.

ELECTRONIC PERSONAL DOSEMETER HANDBOOK

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 rea d data from store an d to write data to store so that EPD parameters, operat io nal c ontrol 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 but ton.

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

maintaining, configurin g and readin g EPDs. Th e IR communication r ange 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-o ut from the last communication after which the EPD reverts to normal display. There is also an inhibit timer that prevents an EPD from re-establishing communications immediately after

is a Thermo PC-based software product for

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TECHNICAL DESCRIPTION

communications are completed. This gives the user time to remove t he EPD from the IR field. The EPD continues to measure radiation during commu nic ation.

4.5.2 EPD Configuration via the IR Communications Links

Communication via the EPD’s IR communications link will allow access to the following EPD functions and displays:

♦ Default Display

EPD/HB/40521/000

♦

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

Access to these configuration parameters is restricted as follows:

1) CALIBRATION FACTORS: Write access to calibration parameters is pre ven te d un le ss th e EPD is

configured by the manufacturer with calibr ation parameters unlocked (default is locked). If the calibration parameters are un lo cked the n suit able s/ w ava ilable through Thermo can adjust the ‘gains ’ of the EPD calibration within specified % limits from the original manufacturer’s calibration.

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2) PTB APPROVED EPD

The Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, is the national institute of natural and engineering sciences and the highest technical authority for met rology and phys ical safety engineering of the Federal Republic of Germany.

EPDs supplied to Germany and elsewhere under PTB approval are specially configured by the manufacturer to en sur e cer tain functions cannot be enabled, as follows:

Alarm Configuration Alarms cannot be configured Off, be disabled, set to quiet or low frequency.

This ensures that Alarm sound le vel is >85dB(A) at 30cm from the EPD. The alarm times cannot be set to less than 10 minutes.

The following Alarm Control set tings may also not be changed f rom the factor y configuration: Battery alarm level 1, Battery Alarm Level 2, Battery Type Discriminator, Regulated voltage a lar m level.

LCD, Decimal Point position and display units. PTB EPDs are configured such that the settings for de cimal places, dos e units,

off display, wearer display, overr ange fl ashing, an d 1 minute lo gging, cannot be changed.

EPDs are factory configur ed to the required Display Settings and then 'locked' in that condition. This configuration is required for PTB approved EPDs.

Calibration Factors Beta/Gamma EPDs are supplied with calibration fa ct or s locked. Any attempt to configure PTB Approved EPDs contrary to this specification will

fail. If the configuration is attempted using EasyEPD2 then EasyEPD2 will display gives the error message 2 28.

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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 1 to 579 records for transitions up to 127 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.

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TECHNICAL DESCRIPTION

µSv. Store for up

Sv or

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 Dose Rate Alarms: 0µSv to 16Sv and 0µSv /h to 16µSv/h

Recommended minimum settings to avoid

Alarm Types: Audible and visual alarms for dose, dose

Tones: High/low tones, loud/quiet volume in seven

resolution V 1/64µSv and 1µSv/h

false alarm 7µSv/h Hp(10)/h and 100µSv/h Hp(0.07)/h

rate, count-down timer, read time and failure mode. Alarms are configurable via the IR communications link.

combinations of continuous or fast/slow intermittent.

Hp(10) Dose Chirp: Settable from 0.01

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. User-selected displays have a time-out period, wh ich can be set between 10 to 99 seconds. This time-out is the period of time that any display select ed 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 tha t 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-is sued 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 commun ications link.

Sv/chirp.

µSv/chirp to 100

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4.6.5 Dose and Dose Rate

EPD/HB/40521/000

TECHNICAL DESCRIPTION

The EPD calculates dose and d ose rate. Dose is ac cumulated in 3 stores:

Total Dose

and

Dose

The EPD displays Hp(10) (penet rating or deep) dose and Hp(0.07) ( superficial or shallow) dose. 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 is displayed as a decimal equivalent. Total Do se is a store providing a long-term record of dose accumulated by the EPD. range between 1

Accumulated dose is written to non-volatile memory at least every 15 minutes. Therefore is a reset occurs, due to the battery cap being removed or the EPD being heavily dropped, or a passivated battery fitted, up to 15 minutes of accumulated dose may be lost. Such events howe ver ar e detect ed and a count of resets provided as quality data associat ed with t he accumula ted do se, see se ction

4.6.7. Note that from software version 11 EPDs it is possible to configure the EPD to

make additional logs to the non-volatile memory at 1 minute intervals if the dose received in the preceding minute exceeds 1 uSv.

Display characteristics that can be set are:

Units Sv or rem

ADS Dose

Dose

is regarded as a short-term record of dose received, usually

Dose, Total Dose

Sv to 16Sv (maximum resolution 1µSv).

. Dose rate is the current rate calculated by the EPD.

ADS Dose

and

in units of 1/64µSv, although this

The LCD display can be set to auto-

Dose

Decimal Places: 2 or 3 decimal places Resolution: Default Time: 10 to 99 seconds

Note: For Gamma dose, two counts are appr oximately equivalent to 1/64

for Beta dose one count is approximately 1/6 inaccuracies doses should only be displayed in micro sieverts (or 0.1 rem), but when summing a number of d oses the full resolut ion should be used to minimize rounding errors.

Dose Rate

This is the current dose rate as calculated by th e EPD. It may be viewed on the display or read via the IR communications link. Dose rates are calculated using an averaging algorithm to re duce statistical variations to within ±20% under mo st conditions. This results in increased averagin g time constants at low dose rates.

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Sv or mSv

ISSUE 5

Sv and

Sv. To avoid statistical

EPD/HB/40521/ 000

TECHNICAL DESCRIPTION

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 us ed 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 t ime. The dose rate displays on the LCD are limited to 2 significant digits.

Longer time constants have to be used when a veraging the beta dose due to the lower sensitivity of the beta detectors. The time co nstant used maximises at 100 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 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 th e EPD since this value was last cleared is termed the peak dose r ate. The peak dose rates and t he 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.

ELECTRONIC PERSONAL DOSEMETER HANDBOOK

typically under-responds by up to 25% in

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 de te cto r s . The EPD calculates the Hp(10) and Hp(0.0 7) doses by weighted summing (ratios

set during calibration) of the count s r ece ive d on t h e fo ur de t ector channels. Counts can only be read via the IR communications link, although the least

significant digits are visible on the interna l cou nt s displa y ( sect io n 3.5 ).

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4.6.7 Dose Quality Flags

There are 7 dose quality flags set within t he EPD. Dose quality can only be read and cleared via the IR communications link. They are normally cleared with the dose and detector counters at the start of an Issue period, e. g. by Access Control or Issue/Return software. In ‘dose of record’ systems, EPD dose, detector counters and quality factors are all read together and stored on the system database to allow later integrity c hecking of the dose recorded. The dose qu ality flags are as follows:

(i) Reset Count

The reset count is a count of the n umber of times the unit has been reset, eithe r by:

(a) removing and re-fitting the bat tery, or battery cap, (b) use of an unsuitable or passivated Lithium battery, (c) b y a commanded reset via the IR communications link, (d) by a software reset, (e) by a f au lt condition. Note that the EPD loses recent dose received since the last log of dose to non-

volatile memory, as described in section 4.6.5.

EPD/HB/40521/000

TECHNICAL DESCRIPTION

(ii) Knock Time Seconds

The EPD detectors are susceptible to large mechanical shocks. This is overcome by detecting the shock with a piezo ‘knock’ detector. The EPD continues to accumulate dose during the shock period, but at the dose rate that was present immediately before the knock was detected. However, if the dose rate is greater than approximately 4mSv/h the cou nts caused by the knock will be small relative to the radiation count s a nd t her efor e a ll count s are used in the calculat io n of dose . Knock Time is the time period over which knock processing has taken place. Continuous Knock detection for greater than 15 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).

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(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 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 a larm has been activated. An abuse alarm is activated if mechanical knocks are detected continuously for greater than 15 seconds (see

Knock 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 up to 15 minutes of dose may be lost.

(viii) Low Voltage (EPD software version 11 and later)

The EPD analogue circuitry detected a low supply voltag e con dition .

(ix) Detector Fault (EPD software version 11 and later)

The EPD ‘flash LED’ detector test fail ed.

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 I R communication s link at the start of an issue period:

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TECHNICAL DESCRIPTION

♦

Three Dose alarm flags indicate that a dose has exceeded the

corresponding dose alarm thresholds. There are 1

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 1

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 2

1 and the 2

alarm threshold (dose or dose rate) always has a higher priority than the

alarm threshold. The 1st alarm threshold can be considered as a warning value

alarm threshold as a crit ical value. Therefore , the 2nd alarm threshold

should always be set to the higher value. Dose rate alarms can be configur ed to wor k with hyst eresis. 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 t he EPD will set an alarm flag and the sounde r 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.

Alarm thresholds are set via the IR communications link, or by the button if the user is granted authority (see Figur e 3.4), to any value in the following ranges:

Hp(0.07)/h 1 Hp(0.07)

& 2

& 2nd Hp(10)

Hp(10)/h

Sv/h to 16.777215 Sv/h

µSv/h to 16.777215 Sv/h

Sv to 16.777215 Sv

µSv to 16.777215 Sv

It is not recommended to set dose rate alarms to less than 7uSv/h (Hp10)/h or

100

Sv/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 EPD State Alarms

♦ Warnings

♦

Faults

♦ Event history

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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:

Issue Count. This is the number of times the EPD has been issued. Issued

. This is the present state of the issued flag, either EPD

Detectors State. This is the current state of the EPD’s operating mode,

Issued or EPD Not Issued.

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:

3 Dose Alarm Flags 3 Dose Rate Alarm Flags Return For Read. The EPD clock has exceed the Return For

Faults

The EPD retains a record of the following faults flags:

Event Logged

Connection Failed. Communication with the EPD failed. Cal Factors Bad

As section 4.6.8

. As section 4.6.8

Read time.

. An event (possibly but not necessarily a fault)

has been logged in the EPD’s event store.

. The EPD calibration factors failed a CRC

check and cannot be recovered from secure store.

EEPROM Fail. An un-recoverable EPD secure store failure

occurred.

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5. Bad Sectors. The number of bad EPD secure store sectors.

There is a maximum of nine spare sectors.

EPD/HB/40521/000

TECHNICAL DESCRIPTION

9. 10

Detector Test Fail

. The EPD detector test was run and the

number of counts received were less than required to pass the test.

Detector Threshold Fail

. The EPD detector thresholds failed to load

successfully

Radio Fail. Reserved for future use. Other Fault Disabled

. A fault occurred causing the EPD to reset.

. The EPD is not calculating dose.

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TECHNICAL DESCRIPTION

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

Note:

A dose profile interval of zero seconds turn s off the dose profile function.

Dose profile can only be read via the IR communications link. Dose prof ile may be synchronised to a particular time in the future, e.g. hourly logging on the hour.

Note

: The EPD has no conce pt of real-time but maintains a one-second tick that

is valid as long as the EPD is powered and not reset.

Sv or less.

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4.6.11 Event History Store

The EPD logs up to 23 events in non-volat ile store, together with a time stamp. These comprise alarm and fault events see tables 4.1 and 5.2. From software version 11, EPD ON and OFF events are also recorded ( s e e Table 4. 1) .

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 re cor d ed.

Events On Events Off

Code

Text as displayed by

EasyEPD2

200 Failure Alarm on 220 Clear Faults 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 219 Detectors ON* 239 Detectors OFF*

* Version 11 and later software only

Code Text as displayed by

EasyEPD2

EPD/HB/40521/000

TECHNICAL DESCRIPTION

Other Events

Thermo

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 Stor e .

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TECHNICAL DESCRIPTION

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FAULTS AND RECOVERY ACTIONS

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 t ake n to r est or e t he EPD t o op er a t ion al u se.

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 erro r 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 alar m the sounder can be silenced and the alarm Led extinguished by the action of pr essing 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 sound every 30 seconds thereafter.

An EPD conveys faults to the user by a number of displays, e.g.:

♦ Initialisation Error ( ♦ Communications Error (

♦

Error Code ( Fxxx on the LCD )

♦

Blank Display

♦

Other faults (e.g. display lock-up, n o hea r tbeat etc.)

___ ___ ___ ___

――――

on the LCD )

≡≡≡≡

on the LCD )

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:

Event Logged. An event (dose alarm or a fault) has been logged

in the EPD’s event history store.

EPD/HB/40521/000

10.

Communication Error

. Communication with the EPD failed, typically the

unit was removed from the IR media prematurely.

Cal Factors Bad

. The EPD calibration factors failed a CRC check

and cannot be recovered from secure store.

EEPROM Fail. An un-recoverable EPD secure store failure

occurred.

Bad Sectors

. The number of bad EPD secure store sectors.

There is a maximum of nine spare sectors.

Detector Test Fail. The EPD detector test was r un and the number

of counts received were less than required to pass the test.

Detector Threshold Fail. The EPD detector thresholds failed to load

successfully

Radio Fail Other Fault

. Reserved for future use.

. A fault occurred causing the EPD to reset.

Disabled. The EPD is ‘Off’ ( not calculatin g do se) .

This data may be read and cleared via the IR communications link & EasyEPD2.

5.3.2 Event Hi story store

The EPD logs up to 23 events in a non-volatile store, toget her with a time stamp. The Event History store is accessible when the EPD is interrogated over the IR communications link (e.g. by see Tables 4.1 and 5.2.

The store comprises a circular ‘buffer’, the latest event over-writing the oldest.

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EasyEPD2)

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. Alarm and fault events are recorded,

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FAULTS AND RECOVERY ACTIONS

Note

: The date/t ime data field wraps roun d after 194 days of operat ion. After this

time previous event-associated day/date(s) cannot be considered as accurate. In addition elapsed time du r ing loss of power is not recorded.

5.3.3 Dose Quality Factors

A number of faults and events are coun te d an d r ecorded in association with the measured dose. They are zeroed when the dose is zeroe d an d are subsequently read with the dose. These ar e r eferred to as the dose quality factors and are described in section 4.6.7. Non-zero dose quality factors imply that there may be an error in the dose reading due t o the way the product has been used, rather than due to a fault within the unit. For example, the battery cap may have been used or a passivated battery fitted, causing a reset and potentially lost dose.

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♦

FAULTS AND RECOVERY ACTIONS

5.4 Blank LCD Display and Other Faults

It may also be possible for the EPD to fail wit hout producin g 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 fa ults and the r ecommended course of action is given in the table below.

Symptom 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 Confidence Test

Sound fails to operate in alarm condition

Likely Cause

Battery Failure

Battery cap not corrected seated or battery out of specification

1 second timer error

Muting Disabled

Hardware fault

Sounder Disabled

Recommended Action

Attempt to communicate with the

EPD/HB/40521/000

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.

Attempt to communicate with the EPD via the IR communications link. Replace battery and restart un itsee 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.

Communicate with EPD via the IR communications link. Clear alarm conditions. Enable muting if required. Communicate with the EPD via the IR communications link to access stored data. Contact supplier.

Contact supplier.

Enable sounder if required

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Faulty LED

No visual alarm during Confidence Test

LED fails to operate in alarm condition

Faulty Display

Missing or additional segments on LCD display

Hardware fault

LED Disabled

Contact supplier.

Enable LED if required

Hardware fault

Conf ir m 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:

EPD/HB/40521/000

Initialisation errors typically refer to corruptions to data in the EPD’s non volatile memory (EEPROM). These are fa ults 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:

≡≡≡≡

)

Thermo

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 exa m ple an I ssu e of th e EPD to a per so n.

The error ( which is accompanied by an audible alarm ) alerts the user that the EPD is not in a valid operatio nal sta te. Howev er as de scribed ab ove, the cause is a user / operational problem and not a fault in the EPD.

An EPD will only raise this condition if it is first triggered by the system software, in effect a message is passed 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 no t to remove the EPD from the

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IR field until indicated ( i.e. by the system, through d isplays, Leds e tc. ). However the EPD communications software is toleran t of sh ort 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 ma y indicate a problem in the design of the system software, i.e. the user interface.

If the user or system fails to c lear the alarm in the way described above, then the condition can easily be cleared using Easy EPD2 .

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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 log ged in the Event History store, with date/time data. As an example th e fo llowing shows fa ult F09 5:

A list of EPD error codes is given in Table 5.2. They are divided into blocks according to the software module that ge ner a tes them.

Epd Action

This describes what the EPD does in addition to attemp ting to d isplay 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 for m may be used to log single or multiple faults. The completed form sho uld be copied to the supplier of the EPD ( Thermo 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 oper ation and IR communications are unaffected. This includes many Fxxx codes displayed on the LCD. Data should be extracted and logged as f ollo ws:

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 dos e- r at e /t ime dat a ( if a spur ious dose f ault is susp ect ed ) .

5. Dose profile da t a ( if a spuriou s dose fa ult 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 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 retur n in g th e un it to the supplier ( Thermo or other Supplier or Distributo r ) .

3. If the unit is to be restored to operational u se, clear down all faults on display and in the Fault Status Record, using EasyEPD2. This is to ensure that any subsequent faults are de tected.

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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. Supplie r 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)

EPD/HB/40521/000

Comms Module

Code

020 Comms Module Error Reserved for future use

Text as displayed by EasyEPD2

EPD Action

Recommended Customer Action

Remarks

Thermo

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FAULTS AND RECOVERY ACTIONS

Services Module

Text as displayed by

Code

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.

Remarks

This indicates a software fault. This indicates a software fault. This indicates a software fault.

User I/F Module

Text as displayed by

Code

EasyEPD2

040 User Interface Module

Error

Sounder Module

Code

Text as displayed by

EasyEPD2

050 Sounder Module Error Reserved for future use

EPD Action

Reserved for future use

EPD Action

Recommended Customer Action

Remarks

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FAULTS AND RECOVERY ACTIONS

EEPROM Module

Text as displayed by

Code

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

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

Remarks

been 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 faults.

EPD/HB/40521/000

Data Module

Thermo

Text as displayed by

Code

EasyEPD2

070 Data Module Error Reserved for future use

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EPD Action

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FAULTS AND RECOVERY ACTIONS

Counts Module

Text as displayed by

Code

EasyEPD2

081 Unexpected Texas chip

reset (Battery Low but no Batt Low Status)

082 Consecutive Drop (more

than 15 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

15 consecutive seconds of knocks)

EPD Action

Reset unit.

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

Recommended

Customer Action

Return to supplier if recurs.

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 counts ( 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

Text as displayed by

Code

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 logged

EPD Action

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-

Recommended

Customer Action

Reset unit. Return to supplier if recurs.

-ditto- -ditto-

-ditto- -dittoReset 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

Thermo

Text as displayed by

Code

EasyEPD2

100 IRDA Module Error Reserved for future use

EPD Action

Recommended Customer Action

Remarks

Table 5.2 EPD Faults Logged to History Event Store.

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ELECTRONIC PERSONAL DOSEMETER HANDBOOK

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 che ck th e 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 unchang ed throughout t he life of the EPD - p rovided the EPD remains undamaged.

Thermo normal policy is to supply EPDs with the calibration factors locked to prevent their subsequent modification, other than by Thermo. However where expressly requested by customers in t heir purchase order, EP Ds 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:

EPD/HB/40521/000

MAINTENANCE

Thermo

DISCLAIMER

The EPDs within this shipment have been calibrated using the factors as defined on the supplied Calibration Cer tificate. As th e calibr atio n is NOT LO CKED Thermo has no control over any subsequent adjust ments made by the end user to these factors. Thermo can therefore not warrant the calibration of these EPDs once they have left the factory. As such, Thermo accepts no liability for the accuracy of the radiological response of these EPDs.

EPD calibration may be checked using a Thermo irradiato r, 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 an nua lly.

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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 for repair, recalibration or replacement.

During calibration the calibration constants, and the threshold levels for each of the four channels are set. The thre shold levels de termin e 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

the four detector channels into dose equivalent s. These constants are:

HGSens10 SGSens10 HGSens07 SGSens07

ELECTRONIC PERSONAL DOSEMETER HANDBOOK

. Calibration constants c onve r t the counts accumulated on

FBSens07 BCSens07

Where EPDs are provided wit h calibration in the unlocked state (see above), it is these six factors which may be adjusted within the defined percentages from the manufacturers original calibration. These ‘gain’ adjustments are made using software facilities available via Thermo Electron but should only be consid ered in consultation with Thermo.

Detector Thresholds

. Detector thresholds discriminate between r adiation 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)

From software version 11 the detector thresholds were changed to improve the precision and accessible range. No facilities are provided to adjust the detector thresholds and these can only be set by the man uf act u r er .

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MAINTENANCE

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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 batter y (see Sect ion 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:

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 replacem ent ba tteries:

Other AA batteries may be suitable, but Thermo should first be consulted, especially in the case of Lithium batteries. The user is also advised that:

1. The lengt h of the battery including the battery anode (pip) should be in the range of 49.0 mm to 51.0 mm.

if in doubt - remove the battery

Sonnenschien - Lithium 3.6 V (SL-760) Duracell/Procell - Alkaline 1.5 V (MN 1500)

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 / r e placing 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 ma y leak, especially LTC batteries. Batteries should also be r emoved from any EPD that is going to be left non-operatio nal for any length of time to avoid the possibility th at leakage may occur and damage the EPD.

6.2.3 Lithium Thionyl Chloride Battery Warning

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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.

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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 cir cumst an ces.

♦

♦ opened, punctured, crushed or ta mpe r ed with.

3. Batteries in storage should be kept in an isolated, dry, well ventilated cool

4. Batteries are susceptible to fire and abuse. Some manufacturers provide

5. Electrolyte leakage can norma lly be detected by th e smell of sulphur dioxide

6. Batteries must be disposed of in accordance with the manufacturer’s

7. If LTC batteries are to be transpo rted by aircraft the batteries must be in their

used in excess of +70°C and never exp osed to temperatures in excess of +100°C.

environment and kept out of dir ect sunlight. Storage temperatures should be below +30°C.

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 th at could affect the battery , care must be exercised d uring batte ry replacem ent. The battery may have vented into the EPD case and caused the EPD to become pressurized.

and/or the presence of electrolyte solut es. If a leakage is suspected:

(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.

recommendation and Local/Nationa l regulations.

correct packaging.

ELECTRONIC PERSONAL DOSEMETER HANDBOOK

WARNING

6.2.4 Replacing the EPD Battery

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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). Dur ing fitment of the battery cap the EPD will begin its initialisatio n sequence. This is intentional and performs the f unction of EPD start-up. The procedure to replace/insert an EPD battery is described in Section 2.1.2. The initialisation/st art-up sequence is described in Section 2.1.3.

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6.3 EPD Clip Assembly

Depending on customer requirement s, 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 ga r m en t ( s e e Sect io n 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.

ELECTRONIC PERSONAL DOSEMETER HANDBOOK

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 Figu re 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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Thermo Electron EPD MK2 Technical Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

CONTENTS

INTRODUCTION

GETTING STARTED

OPERATING INSTRUCTIONS

TECHNICAL DESCRIPTION

MAINTENANCE