Meters and dosimeters have separate roles in indicating the presence of hazardous radiation levels and are critical life-saving tools in nuclear emergencies.

Survey Meters

The following instruments measure exposure rate or the intensity of radiation at a location at some point in time: survey meters, field survey meters, rate meters, radiac meters, radiation detection meters, low-range meters, high-range meters, airborne meters, fallout meters, remote monitors, Geiger counters, and even dose rate meters.

Like the speedometer of a car shows miles/hr, they all show measurements relative to time, such as R/hr or mR/hr. If you enter a radioactive area and your meter displays 60 R/hr, then it means you will be exposed to 60 R if you stay for a whole hour. In general, survey meters are used to measure high levels of radiation, such as when you measure exposure rate or the intensity of radiation in an area.

Geiger Counters

The Geiger counter also measures exposure rate or the intensity of radiation at a location at some point in time. However, it utilizes a Geiger tube rather than an ion chamber. Geiger counters measure low levels of radiation, such as looking for surface contamination.

Dosimeters

Dosimeters can be in the form of a sticker, badge, pen/tube type, or even a digital readout. They all measure the total accumulated amount of radiation to which you were exposed. Similar to the odometer of a car, they measure an accumulation of units. Dosimeters will indicate a certain total number of R or mR exposure received, just as the car odometer registers miles traveled.

Example of the relationship between a survey meter and a dosimeter

Imagine yourself taking both a survey meter and a dosimeter into an area of measurable radiation. Your survey meter says you are standing in a 30 R/hr radiation field, and you stay for two hours. As you leave, your dosimeter indicates 60 R. The meter measured the exposure rate or intensity of the radiation in the area and the dosimeter accumulated the total amount of radiation you were exposed to in the two hours. If you had left after only half an hour, your dosimeter would have shown 15 R.