Introduction to Dosimeter Fundamentals - bartlettams.com · Introduction to Dosimeter Fundamentals...

Introduction to Dosimeter, Reader & Software Fundamentals

Introduction to Dosimeter Fundamentals

MGP Instruments Learning Center Training Module


About this documentAbout this document

The contents of this document are the sole ownership of MGP Instruments and shall not be reproduced, distributed, altered or modified without the consent of MGP Instruments, Inc.

Modification to the information presented in this document may result in inaccurate operation of associated hardware and software.


IntroductionIntroduction

• This session is designed to provide the attendee a basic overview of features and operation of the DMC-2000S electronic dosimeter

• This session is prepared for individuals who are responsible formaintenance and oversight of electronic dosimeter use.

• This session does not provide guidance in repair, calibration oradvanced use of configuration software. However, it provides the tools for the attendee to be knowledgeable in the basic dosimeter operation, maintenance, and troubleshooting techniques.


AgendaAgenda

1. Electronic Dosimeter Theory, Features and Function

2. Operational Modes

3. Maintenance and Troubleshooting


Section 1:

Theory, Features and Functions of the DMC-2000

Section 1:

Theory, Features and Functions of the DMC-2000


DMC 2000S OverviewDMC 2000S Overview

General Features

• Solid State (silicon diode) detector

• Personnel & Area Monitoring capability

• Linear dose rate response to 1000 R/hr

• Energy Range: 50 keV - 6 MeV

• Self Testing/Diagnostics (battery, detector)

• Internal Memory “Histogram”

• Multi-Configuration:

- Dose, Rate and Time Alarm/Warning

- Satellite or Autonomous operation

- Hands-Free communication

• Small and lightweight - 56 grams (with battery)

• Rugged…

- surface-mount circuit board

- durable, high resistant ABS plastic

• Standard battery (Renata CR2450N) –2000+ hours life

• RF Resistant

• Waterproof - tested at 1 meter for 2 hrs


DMC 2000S Overview – cont.DMC 2000S Overview – cont.

General Features – cont.

• Alarm Thresholds- Primary Alarm for Dose and Dose Rate- Pre-Alarms (warnings) for Dose and Dose

Rate- Time

• Histogram – “Events History”- ~700 intervals- 10 sec, 1 min, 10 min, 1 hr, 24 hr- Stamps dose increment, date, time at

selected time interval; records alarm or error indication automatically

• Optical Detector Check- Expose diode to light source every 10

minutes- Three consecutive failures, detector fault

alarm (def det)

• Background Radiation Check- 10 uR/hr x 300 cps/hr = 0.003 cps or ~2

cpm- No counts in pre-determined time: det.

Fault- For 0.5% false positive error, circuit looks

for a count every 2.5 hours (9,000 seconds)

• Battery Voltage check every 10 minutes- New battery: 3.0 volts (CR 2450)- Low battery state: 2.7 volts- Battery fault: 2.5 volts- 460 days continuous operation in

background dose rates with no alarms - 30 days continuous operation in 100 mR/hr

field with audible and visual alarms - 188.5 days continuous operation with 10%

alarm condition



Measurement Range

• Dose Rate Response: Accurate for > 10 mrem/hr. Between 0.1 and 10 mrem/hr, does not indicate +/- 20% of true rate

• Dose Response: When exposed to 0.1 mrem/hr for 1 hour, dosimeters accurately indicated a dose of 0.1 mrem

• Additional Specifications and Test Reports can be obtained via the web at: www.mgpi.com

Microprocessor Functions

• Counts pulses• Converts to dose• Calculates dose rate• Keeps time• Drives display• Alarm logic• Reader communication• Manages EEPROM• Micro-phonics compensation• Controls RS-232 Output Stores internal

parameters (ROM)• Stores temporary parameters (RAM)

Audible Alarm Intensity• Alarm frequency measured at ear location

when worn normally: approximately 5,300 Hz

• Sound pressure level measured at 30 cm in front of speaker: - 2000S: 85-90 dBa (dose) and 85-90 dBa (rate)- DMC/CTM: 80-83 dBa (dose) and 77-80 dBa

(rate)Standards are 80 - 85 dBa



General Features – cont.

Speaker Port Battery Cover

ISO Connector

Removable Clip

Push-Button

DetectorLocation“+”

Display

IR Ports – 3(hole in clip for center IR port)

SerialNumber

Position “notches”for external devices (transmitter, etc.)


DMC 2000S DetectionDMC 2000S Detection

DMC 2000S DETECTOR BOARD

Speaker & Battery Compartment

Circuit Board

Detector Assembly

Micro-processor

Capacitor


DMC 2000S Detection – cont.DMC 2000S Detection – cont.

Energy Compensation Shield

Silicon Diode Detector

Optical Test DiodeDetector Element

DMC 2000S Detector Assembly

Flash LED


DMC 2000S Detection – cont.DMC 2000S Detection – cont.

Detector

Empty Region

(Interaction Zone)

++

Bias Voltage(2.5V)

Pulse Pre-Amp(Detector Board)

To Detector Board

P-Region

+ + + + + + + + ++ + + + + + + + ++ + + + + + + + ++ + + + + + + + +

N-Region

-- -- -- -- -- -- -- ---- -- -- -- -- -- -- --

Incident Gamma

Silicon Diode DetectorWhen gamma radiation interacts with the mass in the vicinity of this region, charged particles are created in the empty region. A small charge is created and collected by the polarization voltage, thus producing a small pulse across the diode. This pulse is fed “downstream” to a discriminator / preamplifier circuit and eventually to the amplifier

The preamplifier converts the charge to an electrical pulse and the discriminator eliminates signals due to electrical noise. The amplifier then produces a pulse of significant amplitude for the microprocessor to count. The number of particles generated in the detector is proportional to the incident radiation and the mass of the material in close proximity of the detector. The detector shielding is one of the reasons why the dosimeter is accurate. It ensures that the response of the detector, that is number of pulses per mrem/hour of exposure rate of a given energy, is approximately constant.


DMC 2000S Mode DisplayDMC 2000S Mode Display

EXT

PAUSE DisplayedDeactivated mode - “OFF”

..or custom User display(Cal Due Date, Serial Number,

etc…)

PAUSE DisplayedPAUSE DisplayedDeactivated mode Deactivated mode -- ““OFFOFF””

..or custom User display..or custom User display(Cal Due Date, Serial Number, (Cal Due Date, Serial Number,

etcetc……))

“D” – Dosemrem – incremental dose

““DD”” –– DoseDosemrem mrem –– incremental dose incremental dose

“R” – Dose Ratemrem/h – rate of exposure

““RR”” –– Dose RateDose Ratemrem/h mrem/h –– rate of exposurerate of exposure

PAUSE Mode RUN Mode


DMC 2000S Mode Display – cont.DMC 2000S Mode Display – cont.

ALARM Display

DOSE AlarmDOSE AlarmDOSE Alarm RATE AlarmRATE AlarmRATE Alarm


DMC 2000S Mode Display - cont.DMC 2000S Mode Display - cont.

Low Battery Status Message

In PAUSE Mode… In RUN Mode…

BA LO display indicatesapprox. 72 hours of

remaining battery life. The BA LO message

alternates with the PAUSE display. The battery life (hours) is not displayed.

BA LO display indicatesBA LO display indicatesapprox. 72 hours of approx. 72 hours of

remaining battery life. The remaining battery life. The BA LO message BA LO message

alternates with the PAUSE alternates with the PAUSE display. The battery life display. The battery life (hours) is not displayed.(hours) is not displayed.

BA LO display indicatesapprox. 9 hours of

remaining battery life. The BA LO message performs an

hourly countdown and alternates with the PAUSE

display.

BA LO display indicatesBA LO display indicatesapprox. 9 hours of approx. 9 hours of

remaining battery life. The remaining battery life. The BA LO message performs an BA LO message performs an

hourly countdown and hourly countdown and alternates with the PAUSE alternates with the PAUSE

display.display.

Note: a Low Battery alarm occurs when the voltage has dropped to 2.7 volts. Further reduction in voltage (2.5 volts) results in a blank display and loss of power.

Typical operating voltage is in the 3.0 to 3.2 range.


DMC 2000S Mode Display – cont.DMC 2000S Mode Display – cont.

Display Messages – Internal Faults

Defective Detector:Remove from serviceReturn for repair/replacement

Defective History:Start new histogram using Reader – Entry/Exit

Defective Battery:Battery discharged/removed;Change battery, check for short Or defective ground wire

Defective EEPROM:Problem accessing data in Memory; remove battery for72 hrs,reinstall

Defective Calibration:Calibration data integrityproblem; re-calibrate dosimeter

Defective Componentfor Pulse Counting:Remove from service; return For repair/replacement

Defective External Detector/Initialization:External detector calibration value corrupted; Data integrity suspect or corrupted; re-initialize calibration or system parameters. ContactMGPI for help

Drained Battery:Remove battery for 72 hrs; inspect for damage

Refer to Troubleshooting Section of this ModuleRefer to Troubleshooting Section of this ModuleRefer to Troubleshooting Section of this Module


Section 2:

Operation Modes of the DMC-2000

Section 2:

Operation Modes of the DMC-2000


DMC-2000 OperationDMC-2000 Operation

The DMC-2000 operates in two distinctive modes:

• Satellite Mode• Autonomous Mode

The Satellite Mode of operation requires a dosimeter reader for activation, deactivation and programming. This mode is typically used in a facility (e.g.; nuclear power plants, other licensed facilities, etc.) which utilizes exposure records management software to automatically program the dosimeter for use.

The Autonomous Mode of operation permits the user to manually activate, deactivate and configure specific parameters using the push button.

This section describes both operational modes.


DMC 2000S Display – cont.DMC 2000S Display – cont.

Display Device Parameters – Satellite Mode:

Serial Number

Cumulative Dose

Maximum Rate

Time

Dose Alarm Threshold

Dose Rate Alarm Threshold

Audible Alarm Mode

Operating Mode

External Detector



Active Information Display: Alarm Set-points

Note: When the DMC-2000 is active or in the run mode, the user can display the Dose, Dose Rate alarms configured for the dosimeter.

If the dosimeter is configured for Time and Pre-alarms (warnings), then these additional set-points will automatically be displayed

1. Press & Hold Button for 8-10 seconds

2. Display shows Dose Alarm(maintain pressing button)

3. Display shows Dose Rate Alarm(maintain pressing button to cycle through set points again, or…)

4. Release button to return to active display

Display Device Parameters – Satellite Mode:



Display Device Parameters – Autonomous Mode:

Serial Number

Cumulative Dose

Maximum Rate

Time

Dose Alarm Threshold

Dose Rate Alarm Threshold

Audible Alarm Mode

Operating Mode

EXT

Reset or Total

Parameter Modification

Change

External Detector


DMC-2000: Autonomous OperationDMC-2000: Autonomous Operation

1. Press Button Once

2. Display changes to CHANGE

3. Display changes to ENTER- Press Button Once

4. Display changes to IN- Beep, LED Flash

5. Dosimeter Active

EXT

Note: The dosimeter pushbutton may be rigid or stiff upon first use, and seem difficult to operate.

After time, the pushbutton will soften, permitting ease of use when activating and deactivating the dosimeter

Activating the DMC-2000S – from PAUSE to RUN:


DMC-2000: Autonomous Operation – cont.DMC-2000: Autonomous Operation – cont.

Active Information Display

1. Display Dose - mrem


3. Display changes to Rate - mrem/h


5. Display changes to Dose – mrem

Note: The dosimeter can be configured to display the dose and rate values either manually or automatically.

These parameters can be configured using the DOSIMASS software utility (requires a Reader)



Active Information Display: Display Set Points

Note: While the DMC-2000 is active or in the run mode, the user can display the Dose, Dose Rate alarms and configured for the dosimeter.

A steady press of the button must be applied.

If the dosimeter is configured for Time and Pre-alarms (warnings), then these additional set-points will automatically be displayed


- Display changes to CHANGE(maintain pressing button)

- Display changes to GO OUT(maintain pressing button)

2. Display shows Dose Alarm(maintain pressing button)

3. Display shows Dose Rate Alarm(maintain pressing button to cycle through set points again, or…)

4. Release button to return to active display



Deactivating the DMC-2000S – from RUN To PAUSE:


- Display changes to CHANGE(maintain pressing button)

2. Display changes to GO OUT- Release Button

- Display changes to OUT- Beep, LED Flash

3. Dosimeter Deactivated (Pause)

EXT

Note: A steady press of the button must be applied.

If you notice the display change while holding the button, release and start the process again to initiate deactivation.



In the Autonomous Mode of operation, specific parameters can be modified using the push-button:

- Dose Alarm, Dose Warning- Dose Rate Alarm, Dose Rate Warning- Keep or Clear previous Cumulative Dose on Entry- Fast Entry

The following slides provide instruction in this process.

Manually Modifying Parameters



EXT

1. Start from PAUSE mode- Press button once

2 Display changes to CHANGE- Press button once

3 Display changes to MODIF

4 When ENTER is displayed, press button to access modification mode

5 Press button – Serial Number is displayed

6 Press button – RESET is display with a flashing “P”

Note: Modifying the parameters requires continuous selector button presses.

The dosimeter will return to the PAUSE display if the selector button has not been pressed after 5-10 seconds.

This process takes practice and patience

Manually Modifying Parameters – cont.




At this point, the flashing “P” indicates that the dosimeter parameters can be modified. The process is three-fold:

- Toggling the display to a specific parameter Flashing P

- Selecting the digit to be modified Flashing D

- Changing the digit increment Flashing I




To change Dose Reset (re-zeroes dose when dosimeter is deactivated) to Dose Total (accumulates dose total each time dosimeter is turned on):

1. From the flashing “P” on the RESET display:

2. Hold the button until the “P” changes to “I”.

3. When the “I” flashes, press button once to change to total. Press and hold button to change I to P to continue parameter changes.

4. Continuously press button to cycle to the desired parameter to modify while the “P” flashes.




When the desired parameter is displayed, perform the following to modify the values:

P – Select ParameterPress the button continuously to select the desired parameter to bemodified. When the selected parameter is displayed…- Hold button down until “P” changes to “D”:

D – Select the Digit of each NumberWhen the “D” flashes, press the button until the desired digit is highlighted. - Hold button down until “D” changes to “I”:

I – Change the Increment of the DigitPress the button to change the digit increment.When completed, hold the button and the display will change from I to D, allowing the user to select another digit to be changed. Repeat process.

When completed, release the button and the dosimeter will return to PAUSE after approximately 10 seconds.


Section 3:

DMC-2000 Maintenance & Troubleshooting

Section 3:

DMC-2000 Maintenance & Troubleshooting


DMC 2000 Maintenance – cont.DMC 2000 Maintenance – cont.

REPLACING THE BATTERY

Battery Cover: use tool to remove, turning

counter-clockwise

Battery Cover: Battery Cover: use tool to remove, turning use tool to remove, turning

countercounter--clockwiseclockwise

Remove Clip First!

Remove Clip Remove Clip First!First!

Use the battery tool (provided by MGP Instruments) to ensure proper removal and replacement of the battery cover.

Use of other tools may result in damage to the case during removal and replacement.

Inspect Compartment…• Ensure O-RING is seated

properly• Ensure presence of insulator• Ensure contacts are secure

Inspect CompartmentInspect Compartment……•• Ensure OEnsure O--RING is seated RING is seated

properlyproperly•• Ensure presence of insulatorEnsure presence of insulator•• Ensure contacts are secureEnsure contacts are secure



REPLACING THE BATTERY – CONT.

Replace with fresh battery in same orientation as removed:

Label / Positive (+) Down…

Replace with fresh battery in Replace with fresh battery in same orientation as removed:same orientation as removed:

Label / Positive (+) DownLabel / Positive (+) Down……Reinstall battery cover

securely. DO NOT TIGHTEN

EXCESSIVELY

Reinstall battery cover Reinstall battery cover securely. securely.

DO NOT TIGHTEN DO NOT TIGHTEN EXCESSIVELYEXCESSIVELY

Note: Use only Renata CR2450N or Toshiba 2450 Batteries.

Do not use reference replacements, such as Duracell, Energizer, Sanyo or Varta as they may result in a loss of power or adverse operation due to incorrect dimensions and positioning.

Renata Duracell Eveready

Remove Clip First!

Remove Clip Remove Clip First!First!



The only replaceable parts on the DMC-2000 are:

• Clip• Battery Cover• Battery• Insulator• O-ring

There are NO internal parts that can be repaired. Removal of the4 screws on the rear case will result in a void of the warranty, as well as compromise the waterproof capability of the dosimeter.

REPLACING PARTS


DMC 2000S Troubleshooting – cont.DMC 2000S Troubleshooting – cont.

TROUBLESHOOTING COMMON FAULT MESSAGES

Defective Detector:Remove from serviceReturn for repair/replacement

Defective History:Start new histogram using Reader – Entry/Exit

Defective Battery:Battery discharged/removed;Change battery, check for short Or defective ground wire

Defective EEPROM:Problem accessing data in Memory; remove battery for72 hrs,reinstall

Defective Calibration:Calibration data integrityproblem; re-calibrate dosimeter

Defective Componentfor Pulse Counting:Remove from service; return For repair/replacement

Defective External Detector/Initialization:External detector calibration value corrupted; Data integrity suspect or corrupted; re-initialize calibration or system parameters. ContactMGPI for help

Drained Battery:Remove battery for 72 hrs; inspect for damage


Troubleshooting – cont.Troubleshooting – cont.

DMC-2000 TROUBLESHOOTING GUIDE



DMC-2000 TROUBLESHOOTING GUIDE – CONT.



DMC-2000 TROUBLESHOOTING GUIDE – CONT.

NOTE: This guide is designed to provide easy troubleshooting and resolution of common dosimeter error messages and faults. Contact an MGP Instruments representative for clarification or further information.


Associated LessonsAssociated Lessons

• DOSIMASS Fundamentals• Reader Fundamentals

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