The device is used in medicine and the military to measure the value of radiation. The dosimeter works on the principle of changes in the substance contained in it. Digital and film dosimeters are currently used. Most dosimeters measure in microSieverts per hour.
A radiation dosimeter is a device that measures dose uptake of external ionizing radiation. It is worn by the person being monitored when used as a personal dosimeter, and is a record of the radiation dose received. Modern electronic personal dosimeters can give a continuous readout of cumulative dose and current dose rate, and can warn the wearer with an audible alarm when a specified dose rate or a cumulative dose is exceeded. Other dosimeters, such as thermoluminescent or film types, require processing after use to reveal the cumulative dose received, and cannot give a current indication of dose while being worn.
The personal ionising radiation dosimeter is of fundamental importance in the disciplines of radiation dosimetry and radiation health physics and is primarily used to estimate the radiation dose deposited in an individual wearing the device.
Ionising radiation damage to the human body is cumulative, and is related to the total dose received, for which the SI unit is the sievert. Radiographers, nuclear power plant workers, doctors using radiotherapy, HAZMAT workers, and other people in situations that involve handling radionuclides are often required to wear dosimeters so a record of occupational exposure can be made. Such devices are known as "legal dosimeters" if they have been approved for use in recording personnel dose for regulatory purposes.
Dosimeters are typically worn on the outside of clothing, a "whole body" dosimeter is worn on the chest or torso to represent dose to the whole body. This location monitors exposure of most vital organs and represents the bulk of body mass. Additional dosimeters can be worn to assess dose to extremities or in radiation fields that vary considerably depending on orientation of the body to the source.