Geiger Counter Vs. Dosimeter: What is the Difference?

Dosimeter and Geiger counter are measuring instruments that measure the amount of radiation in an area. Like the speedometer of your car, they show radiation contamination per hour.

A typical reading from a Dosimeter can be 50R/h. That means if you stay in that area for an hour, your body will be exposed to 50 R. Generally, these instruments measure the level of radiation contamination.

Read on to find out the main difference between a Dosimeter and Geiger Counter, including their working principle.

Geiger Counter

1. What is A Geiger Counter, and How Does it Work?

A Geiger Counter, also known as Geiger Muller Counter or GM Counter, is a traditional device for measuring the exposure rate or intensity of radiation in an area at a given time. It uses a Geiger tube to detect surface contamination by radiation. However, it cannot tell the original source, radiation type, and energy it has.

Geiger Counter is an inexpensive radiation detection device you can buy to help you detect radiation, but how does it work? This instrument consists of two main parts – a sealed tube and a display unit. This sealed tube, also known as the chamber, is full of gas.

The radiation enters the chamber and collides with the gas, which pushes electrons away from the gas atoms. This phenomenon creates an ion pair. A wire in the sealed tube attracts those electrons, creating other ion pairs and making current flow through the wire.

The current created drives a point across the scale or is used to drive a digital display, depending on the type of Geiger Counter. You can hear a beep when an ion pair is created for devices equipped with loudspeakers. The number of beeps tells you how much radiation enters the Geiger chamber.

There is usually background radiation that Geiger Counter detects. These come from the sun, rock, radon, natural uranium, and other sources. Also, it varies from region to region depending on the weather and climatic conditions.

2. Applications of Geiger Counters

Geiger Counters are undoubtedly one of the most popular radiation detection instruments worldwide. These devices have existed for centuries and still have many applications in the modern world, including the following:

Detecting radioactive rocks and minerals in the mines
Hazard management personnel to check for radiation contamination.
Monitoring the level of radiation around a nuclear power plant.

Radiation detection in the scrap metal processing industry
Radiation detection in erstwhile warzones.
Monitoring radiation levels in X-ray rooms in hospitals

Dosimeter

1. What is A Dosimeter, and How Does it Work?

Dosimeters are examples of personal radiation detectors that come in different form-factors. You can find them as a sticker, badge, pen type, or digital readout. Regardless, these instruments measure the total accumulated amount of radiation you are exposed to. Think of it as the odometer of your car that measures the mile coverage since it was manufactured.

For example, a dosimeter reading in an area can indicate 60 R. If the intensity or rate of exposure in that area was 30 R/h, it means you were exposed for two hours. Had you stayed in that area for 3 hours, the accumulated radiation could be 90 R.

A dosimeter detects high-energy beta, gamma, or x-ray radiation. However, it is unable to detect low-energy radiation from some sources such as sulfur-35 and carbon-14. But how does it work?

Dosimeters are different types with unique principles to detect radiation. The most commonly available ones include the following:

Film badges
Optically stimulated luminescence dosimeters

Thermos-luminescent dosimeters
Direct-ion storage dosimeters [Source: ORAU]

The film badge is a single-use dosimeter that detects the amount of radiation exposure. The digital ones provide instant data that can be analyzed using a computer, a smartphone, or other capable devices. On the other hand, thermos-luminescent dosimeters (TLDs) use a lithium fluoride (LiF) or a CaD₂ crystal. They detect radiation by measuring the amount of light emitted by the crystal when heated by radiation.

2. Applications of Dosimeters

Dosimetry is a relatively new technology but has a wide range of applications in radiation detection. Their higher capability and small size make them the preferred choice over Geiger Counters.

Dosimeters are commonly used by workers in unknown radiation situations or emergency response teams. Even military and disaster management personnel wear them when on duty to detect radiation in places of work.

Comparison Chart: Geiger Counter Vs. Dosimeter

Geiger Counter	Dosimeter
Uses a sealed tube filled with gas and a wire inside it to detect radiation	Uses film and filters, aluminum oxide, crystal, or ion chambers and an electronic element to detect radiation dose levels. It depends on the dosimeter type.
Detects radiation around you but cannot tell you the source, type, or energy it contains	Detects and localizes radiation sources from nuclear and radiological dispersal devices
Does not detect uncharged particles such as neutrons.	Some Dosimeters can detect doses due to neutrons.
Relatively bulky and heavy	Compact, lightweight, and portable
Has a wide range of applications and is affordable	Has a wide range of applications but is relatively expensive

Final Remarks

Exposure to large doses of radiation can be fatal. Radiation ionizes living cells, killing them in the process. That is why you should keep away from areas with radiation poisoning. But if you are a worker with a duty to visit such places, have a dosimeter to measure the amount of radiation in the area and stay away if it is above the recommended level for humans. You can also wear or put on dosimeters to measure the radiation exposure level and warn you when it is getting to a dangerous level.

Geiger Counter and dosimeters are all crucial radiation instruments that ensure your safety and other area residents. Despite the differences in capability and operating principles, they all save people from radiation poisoning.

Other related pages:

Best Geiger Counter Reviews

List of Instruments to Measure Ionizing Radiation