A device used to measure the dose of radiation a human being has been exposed to. A personal dosimeter is typically worn by radiation workers, such as doctors in radiology or workers in a nuclear power plant. The dosimeter measures the total dose to which a person has been exposed to during working hours. It is worn on the clothing where it measures the dose to the whole body, but it can also measure the dose to individual parts, e.g. a dosimeter in a ring measures the dose to the hands. Electronic dosimeters allow instant checking of the total dose and can be equipped with an alarm to warn if the permitted value is exceeded. They can be reset after use and used repeatedly. Other types of dosimeters, such as film dosimeters, are disposable and require post-processing to determine the total dose received.