Electronic Personal Dosimeters - Technical Specifications

electronic personal dosimeter

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Front view of a single electronic personal dosimeter (EPD). The EPD is rectangular shaped, off white in color and has a black lid located at the top. It has an orange/reddish circle centered at the bottom and a small orange light slightly above. There is a black circular knob on the left side, near the top and a black oval button on the front side, also near the top of the dosimeter. SIEMENS is written in black capital letters just below the black oval button.

Dosimeter Overview

The Electronic Personal Dosimeter, or the EPD® as it is more commonly called, is a personal radiation monitor that detects and measures beta and photon radiation. Radiation that is detected by the EPD is processed to give a real-time readout to the user via a liquid crystal display (LCD) for deep dose, skin dose and the dose rates.

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 deep and skin dose and dose rate. Other functions include: storage in a memory chip of detected radiation, triggering an alarm when alarm conditions are met and a user interface comprising a LCD display and button.

The EPD calculates both the accumulated dose and the dose rate for deep dose (Hp10) and skin dose (Hp0.07). These, and other data, are stored in an internal store memory chip within the EPD. A button on the EPD case allows the user to retrieve this data from storage, 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. To minimize the loss of data from battery or other failure, data is saved to secure memory within the EPD every 15 minutes.

Audible alarms are triggered if either the accumulated dose or dose rates exceed programmable threshold levels. Clients should inform their Customer Service Representative if they would like a specific alarm configuration.

Dosimeter Reading Equipment

Data is written to and read from the EPD via an integral infra-red communications interface/reader. The Thermo Electron EasyEPD2 software program reads and writes data to the EPD via its infra-red communications link and displays the data in a PC window. The equipment used to configure and read the EPD is licensed to be used solely by the National Dosimetry Services (NDS).

The EPD is returned to NDS for maintenance on a yearly basis. EPDs are subjected to annual calibration and functionality testing before they are sent out to clients. Calibrations are performed by exposing the EPD to a known quantity of radiation and measuring its response; this response is then compared to a calibration verification tolerance of +/-10% to determine a pass/fail.

Accreditations

The EPD is not licensed to be used as a “Dose of Record” and dose data is not sent to the National Dose Registry (NDR). An EPD is meant to be used as a dose management tool and can be used in conjunction with a passive dosimeter (e.g. TLD, InLight dosimeter, etc.).

Technical Specifications

Dosimeter Name
Electronic Personal Dosimeter (EPD®)
Dosimeter Type
Active
Radiation Detected
X-ray, Gamma and Beta
Wear Location
Waist (belt), Shirt (pocket)
Doses Reported
Hp(10), mSv ("Deep Dose" or "Body Dose") and Hp(0.07), mSv ("Shallow Dose" or "Skin Dose")
Energy Response
Gamma, X-Ray: 15 keV to 10 MeV
Beta radiation: 250 keV to 1.5 MeV
Power Supply
Single AA 1.5V alkaline battery for approximately 8 weeks continuous operation, or 3.6 V Lithium battery for approximately 5 months continuous operation
Display Units
Sieverts (Sv) or rem (with prefixes)
Dose Display and Storage
0 µSv to 16 Sv
Display Threshold
1 µSv
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