What’s the Difference Between a Geiger Counter and a Personal Radiation Detector?


It is common in popular culture to refer to all types of radiation detection instruments as Geiger counters. That, however, is a mistake. 

There are different types of radiation detection instruments. Not all of them are Geiger counters. A personal radiation detector (PRD), for example, is different from a Geiger counter. 

Difference Between A Geiger Counter And A Personal Radiation Detector

The U.S. Nuclear Regulatory Commission (USNRC) offers a detailed description of Geiger counter radiation detectors. Also known as Geiger-Müller counter or Geiger tube, this instrument derives its name from its inventor Hans Geiger. 

He later worked with his doctoral student Walther Müller to improve it. It also goes by the name of a G-M tube. 

How A Geiger Müller Counter Works

A Geiger counter is the least expensive electronic radiation detection instrument available. It can inform us when there is radiation around. However, it cannot provide information about the source, type, and energy level of the radiation.

There are two basic parts to a G-M tube. One is the sealed tube, which is a gas-filled chamber with a detector anode inside. The other part is for displaying the information.

A Geiger counter works on a high voltage. Each ionization reaction causes a gas amplification. Irrespective of whether it is due to a single particle interaction or something stronger, the entire detector anode gets charged.   

The electricity produced goes to the display board to move the indicator needle, or display a number. A G-M tube typically displays the number of ions entering the chamber per minute. 

A Geiger counter can detect alpha, beta, and gamma radiation. It cannot, however, distinguish between these radiation types.  

If you keep the loudspeaker on, you can also hear a clicking sound every time an ion pair enters the tube. There is a strong association between the sound of a G-M tube and nuclear weapons. This simple radiation device is very often an indicator of a nuclear disaster. 

Geiger counters are also regularly used to monitor and regulate nuclear waste and nuclear byproducts. Its spheres of application include, without being limited to, hospitals, mines, and nuclear power plants.

Personal Radiation Detectors (PRDs)

A PRD is a device that a person wears, says the USNRC.  A PRD can locate the exact source of radiation, which a G-M tube cannot. That is the main distinction between the two. 

Whenever a person wearing a PRD gets exposed to radiation levels beyond the natural background radiation, the device gives a signal. The signal is usually a flashing light and a tone, and/or vibration.

The biggest advantage of a PRD over a Geiger counter is that the former allows the wearer to address the exact location of the radiation threat. 

Types Of Personal Radiation Detectors (PRDs)

The Radiation Emergency Medical Management (REMM) unit of the US Department of Health & Human Services six different types of PRDs, along with the pros and cons of each. 

  • Personal Dosimeters are small ring-type devices that passively record accumulated personal exposure rate. Their main disadvantage is that there is no real-time display. 
  • Pocket Ionizing Chambers or Self-Reding Pocket dosimeters are devices with real-time display of radiation exposure. These can help monitor varying exposure ranges. 

The usual size of these devices is of a biggish writing pen. Their one limitation is that there is no alarm system. 

  • Electronic personal dosimeters typically get used by workers in known radiation situations. These devices display both the dose and the dose rate in real-time. Some of these also give off an alarm when the exposure rate crosses a preset threshold.  

These, however, are not suitable in situations that need an emergency response.

  • Personal Emergency Radiation Detectors are the most common type used by military and disaster management personnel. Also by others who need to be ready with an emergency response. 
  • These devices are meant for use in harsh environments with high-range exposure. Some variants do not have an alarm option, but most varieties do.
  • Personal Radiation Detectors in the shape and size of pagers are designed to detect the exact source of low-level radiation. Their typical use is by law-enforcement agencies.
  • Extended Range Personal Radiation Detectors are an improved version that facilitates the detection of high dose-rate range. The low-range detection function remains undisturbed. 

It is also possible to categorize PRDs into four types from the perspective of their application. 

  • It is customary to use basic survey meters as PRDs when the exact source of radiation is unknown, or generally present in the environment where the person is. They continue to monitor radiation range. Typical displays include the accumulated dose, dose rate, the gamma count rate, and count rate values.
  • Gamma Surveys are for people working in nuclear power plants, nuclear medicine, or any other profession that implies sustained radiation exposure. 
  • Surface Contamination and Post-Accident Response devices are also often not Geiger counters. However, they are more than PRDs.  
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