How does a Geiger counter work? Its 6 characteristics

Have you ever wondered how a Geiger counter works and how it can be used? how to measure radioactivity? In this article we will look at how a Geiger counter works so that you can easily understand it.

What is a Geiger counter?

A meter or Geiger counter-Müller is a device used to measure and detecting ionising radiation.

Homemade Geiger Counter Radioactivity

Its operation is based on the fact that when the ions that produce these radiations pass through the active volume of the detector they are accelerated by an electric fieldThe current pulse signals the passage of radiation.

Geiger counters are part of a family of radiation detectors called "...".gas detectors". These detectors, as the name suggests, are full of gas (some kind of inert gas at low pressure, about 0.1 atmospheres).

They have an electrode in the centre of the chamber and are configured in such a way that there is an electrical voltage between the electrode and the metal wall of the chamber

This is how a Geiger counter works

At the moment the radiation hits the gas molecules in the tube, separates electrons from atomsThis process is called ionisation. The electron is attracted by the effective charge of the anode and the rest of the atom (a positively charged ion) is thrown towards the tube wall. The electron then travels through the wires that form the electrical circuit and recombines with the ion. Part of the Geiger counter is a device that measures this electron flow.

Geiger-Mueller tube

Of course, it is very difficult to measure a single electronFortunately, the instruments do not need to do so. At the moment the electron and ion are accelerated towards the electrode and the chamber walls gain A LOT of energy due to the high voltage, they collide with other atoms and suppress electrons from in a process called secondary ionisation. Those electrons and, and also ions, in turn, cause even more ionisations and so on repeatedly, this amplifies the original signal at a very high leveluntil it reaches a point where the signal can be measured.

The creation of discrete avalanches in a proportional counter

In a Geiger counter, the voltage is so high that the whole gas chamber is ionisedThis gives a very high sensitivity to the incoming radiation. In other detectors (so-called ion chamber and proportional counters) the voltage is lower and the gas amplification ratio is also lower; only a few gas atoms are ionised in these detectors. The amplification ratio with increasing voltage is shown in the graph below.

Geiger-Mueller Region

To make sense of this graph, mainly by trying to understand how a Geiger counter works and some of its limitations, it is useful to know that alpha particles have considerably more energy than beta particles.

In addition, it helps to know that radiation dose is a measure of the proportion of energy that is deposited by radiation on an element, more energy means more doses.

Thus, looking at this graph, we can see that high energy radiation hitting a detector leaves a higher signal than low energy radiation.

Now look at the right-hand side of the graph, the Geiger-Muller region; in this region high-energy radiation generates exactly the same signal as low-energy radiation. So, we do not have the possibility to distinguish between high-energy radiation and low-energy radiation, which means that we do not have the possibility to always tell how much radiation dose an individual was exposed to if we are only measuring with a Geiger counter. This is one reason why not in all cases we have the possibility to use a Geiger counter to measure the radiation dose rate accurately..

If a Geiger counter, among other things, is calibrated to measure the radiation dose rate of the radionuclide Cs-137, it will be really useful if and when one tries to measure the radiation dose of this nuclide.

So far we have seen how a Geiger counter works in a simple way, but it is important to know that there are drawbacks to this type of radiation meter.

Limitations of Geiger counters

But what if you are trying to measure the radiation from cobalt-60 (Co-60)?

Well, then you're going to have a bit of a snag: the radiation of Co-60 has twice the energy of that of Cs-137so whatever the detector reads will be only half of the actual radiation dose. On the other hand, several radionuclides have lower energy. In such a case, your meter will read a higher dose rate than it is anyway. The end result is that a Geiger counter will only give an accurate radiation dose rate reading if it is measuring exactly the same radioactive material with which it was calibrated.. Hence, Geiger counters are not always the right instruments to measure radiation dose rates.

It turns out that there is a type of Geiger tube that will give very accurate readings of a wide range of radiation energies. energy compensated Geiger counters. These are designed to give a constant reading over a wide range of radiation energies, so if you are using an energy compensated GM detector you can take accurate dose rate readings. Otherwise, it may be better to carry out dose rate measurements with an ion chamber.

One more thing about Geiger counters: They are large general purpose radiation detectors because they have the possibility to measure the alpha, beta and gamma radiation. If you are measuring gamma radiation, you may be more interested in measuring the dose rate (measured in mR/hr or, for really low scenarios, µR/hr - microR per hour). If you are measuring alpha or beta radiation, then you are probably trying to find contamination and should measure counts per minute (cpm) or counts per second (cps), depending on the type of meter you are using.

Summary of the characteristics of a Geiger counter

  1. gas-filled detectors (such as Geiger counters and ion chambers) are filled with a gas to which an electric voltage is applied.
  2. When the radiation interacts with the gas it causes ionisations, and this small signal is amplified by the electric voltage. The amplification ratio is voltage dependent..
  3. Ion chambers have the possibility to measure the difference in the energy of the radiation, which is why they are special measures to measure the radiation dose rate.
  4. Geiger counters, on the other hand, have full signal amplification for any radiation energy that reaches them. For this reason, not all cases give accurate readings of the dose ratemainly if the radiation energy is different from that which was calibrated.
  5. Having said that, GM energy compensated detectors are designed to help solve this problem, now that they offer very accurate dose rates over a wide range of radiation energies.
  6. And finally, Geiger counters also have the possibility of measuring not only radiation dose gamma (measured in mR/hr or µR/hr), but rather in addition to the contamination alpha and beta (measured in cps or cpm).

I hope you enjoyed this basic explanation. If you did not find it enough and you want to learn more about how a Geiger counter works, I recommend you to see this wikipedia article.

Do you want to have your own Geiger-Müller counter?

I bought my Geiger counter as a kit several years ago and it was very easy to assemble. It has been working very well ever since.

If you want to have yours, here you have one. selection of best-selling Geiger counter kits to make it easy for you to find the one that's right for you.

Bestseller No. 1
Shkalacar Tube Radiation Detector, Nuclear Geiger Counter Kit,Assembled Radiation Detector System, DIY Miller Tube Module Experimental Module
  • This kit is compatible with Arduino.
  • 🚗Made of high quality materials, it will not rust and is durable.
  • Supports most Geiger tubes: M4011, STS-5, SBM20, J305, etc. (330 ~ 600 V operating voltage of the Geiger tube can be supported).
  • 🚗Supports computer (PC) data acquisition, analysis and Matlab processing.
  • Good kit for MCU software developers who just want to run Geiger Tube for their own software.
Bestseller No. 2
Handheld Portable Simple Assembled DIY Geiger Counter Kit Nuclear Radiation Detector Module X-Ray X-Ray γ-Ray β Iodine Detection 131 with OLED Display
  • Two forms of alarm: this nuclear radiation detector has a sound and light indication function, the results will alert you in time.
  • Multifunctional tool: has the functions of real-time dose rate, average dose rate, cumulative dose rate, trend graph, etc.
  • OLED display screen: a small OLED screen is adopted to clearly display the measurement results, you can see the data more clearly.
  • The ARM processor is adopted, which has fast operation speed and powerful processing function.
  • Wide applications: this nuclear radiation detector can detect X-rays, γ-rays, β-rays can detect the radioactive dose of marble, jade, Amoy sea products, iodine-131, various unknown minerals for decoration.
Bestseller No. 3
Assembled Radiation Detector System, DIY Miller Tube Tube Nuclear Radiation Detector Geiger Counter Kit Module Experimental Module
  • This kit is compatible with .
  • Made of high quality materials, it will not rust and is durable.
  • Supports most Geiger tubes: M4011, STS-5, SBM20, J305, etc. (330 ~ 600 V operating voltage of the Geiger tube can be supported).
  • Supports PC data acquisition, analysis and Matlab processing.
  • Good kit for MCU software developers who just want to run Geiger Tube for their own software.
Bestseller No. 4
XIYINLI Assembled Radiation Detector System, DIY Miller Tube Tube Nuclear Radiation Detector Geiger Counter Kit Kit Module Experimental Module
  • This kit is Arduino compatible.
  • Made of high quality materials, it will not rust and is durable.
  • Supports most Geiger tubes: M4011, STS-5, SBM20, J305, etc. (330 ~ 600 V operating voltage of the Geiger tube can be supported).
  • Supports PC data acquisition, analysis and Matlab processing.
  • Good kit for MCU software developers who just want to run Geiger Tube for their own software.
Bestseller No. 5
Unassembled DIY Geiger Counter Parts Kit M4011, Module, Nuclear Radiation Detector, X-Ray, X-Ray, γ-Ray, β-Ray
  • SUPPORTS MOST GEIGER TUBES: M4011 can be installed directly, other models cannot be installed on the board, but flying leads can also be used (digital multimeter measures the positive pole of the Geiger tube to the negative pole of the power supply, adjust the blue potentiometer until the multimeter shows DC 170 volts).
  • INTERRUPT OUTPUT SIGNAL: Can be monitored by an external display or a pointer meter. The output signal is interrupt output, the waveform is the falling edge of the pulse and the low level is valid.
  • LOW FAILURE RATE: The circuit structure of the DIY Geiger counterpart kit is stable and the failure rate is extremely low.
  • VARIOUS DETECTIONS: can detect X-rays, gamma rays, beta rays and can perform radioactive dose detection on decorative marbles, antiques, jades, foreign purchased goods, iodine-131 and various unknown minerals.
  • EXCELLENT RESIN MATERIAL: adopt good quality resin material, possess impact resistance, scratch resistance, environmental protection, heat resistant, low temperature resistant, possess excellent electrical properties.
Bestseller No. 6
Geiger Counter Kit Module Geiger Counter Meter Kit USB Visual Alarm Audible Visual Alarm LCD Data Acquisition for Nuclear Radiation Detection
  • Audible and visual alarm: This Geiger counter kit has a built-in audible and visual alarm and its working voltage is 380V-550V.
  • Compatible with most Geiger tubes: This Geiger counter module is compatible with most Geiger tubes M4011, STS 5, SBM20, J305, etc.
  • Function: The Geiger counter kit module is used to detect γ rays from 20 mR/h to 120 mR/h and soft β deflection variables from 100 to 1800, beam spot.
  • Support for computer data acquisition: The Geiger counter module supports computer and PC data acquisition for Matlab analysis and processing.
  • With LCD display: interrupt output interface, through which it can connect to the microcontroller and then display on the LCD.
Bestseller No. 7
Nuclear Radiation Detector, Detector Host, Geiger Counter, β γ-Ray Tester, DIY Radiation Monitor Assembly Kit
  • EASY ASSEMBLY: Nuclear radiation detection module assembly kit, equipped with USB cable, ready to test after assembly (battery not included).
  • RAY DETECTION: it can be used to detect γ-rays from 20 mR/h-120 mR/h and variable β-rays from 100-1800, which has a high accuracy.
  • MULTIPLE FUNCTION: can be connected to MCU for data display, PC data acquisition, for analysis and Matlab processing.
  • GEIGER TUBES: Supports most Geiger tubes, such as M4011, STS 5, SBM20, J305, etc., no replacement restrictions, good compatibility.
  • APPLICABLE SCENES: for detection of home decoration environment, detection of radioactivity of jewellery stones, detection of cosmetic radiation residues, etc.
Bestseller No. 8

Maybe you don't like electronics and gadgetry so much and you prefer to buy a finished Geiger counter. If so, here are these options:

GQ GMC300EPLUS COMPLUSE GEIGER DIGITAL Nulcear Counter Nulcear Radiation Detector Nulcear Radiation Monitor Meter Beta Gamma Dosimeter X-ray data data data monitoring
  • Small Geiger counter holder developed by gQ Electronics USA General indoor and outdoor detection.
  • Audible/visual indicator; Dot Matrix LCD display; real-time recording of data per second to internal flash memory.
  • USB data port for connection to PC/laptop GQ, Geiger counter software.
  • It has large-print text modes for easy reading and easier acquisition of information, e.g. CPM, date, time, elapsed time, USV/h, MR/h, etc.
  • The real-time graphical mode provides a real-time display of radiation level changes, making it easier to observe radiation changes.
GQ GMC-320 Plus Geiger Counter Nuclear Radiation Detector Meter Beta Gamma X ray Europe
  • Small, portable Geiger counter developed by GC Electronics in the USA.
  • Audio/visual indication; LCD dot matrix display, real time recording per second.
  • USB data port for connection/charging with Soft Geiger Counter PC software.
  • Large font size and easy-to-read text mode, maximum data information.
  • Real-time graph mode for displaying real-time fluctuation of radiation.
GQ GMC-500+ Plus - Geiger counter detector for nuclear radiation, for X-rays, beta and gamma rays
  • Independent detection mode
  • Continuous monitoring mode
  • Fast reading in seconds after power on
  • Accurate, real-time data
  • CPM, USV / H, MR / H display on one screen
GQ GMC-320 + V5-UK Digital Geiger Counter WiFi Wireless Wireless Data Wireless Data Dosimeter Radiation Detector
  • Log data through the wireless WiFi connection server and internal memory at the same time.
  • Edifi WiFi ready, keep in touch with Geiger Counter Map of the World
  • Free unlimited online data storage history and unlimited online Geiger Wold map counter service.
  • Real-time evaluation tests, scientific tests on the sample such as: Necessary for the construction of the Hospital Monitoring radiotherapy for cancer, food, water, indoor/outdoor, radiography, and more....
  • Real-time graphic, text and large font mode (radiation data recording and playback again later)
Smart Geiger Pro SGP-001 Radiation Meter for iOS Andriod Smartphone Geiger Counter Radiation Counter Radiation Counter Radiation Detector Geiger Counter
  • Whether synthetic or of natural origin - too much radioactive radiation is harmful. Not only in nuclear power plants, but also in other areas of everyday life Radioactive radiation is produced in various concentrations. among others food, construction and the research sector in varying degrees of these rays hit.
  • For example, check the materials of your living spaces (e.g. the collection of own mineral glaze tiles), clay, some granite, pumice, gypsum, slag, bauxite or red mud containing uranium ...
  • Smart Geiger Pro (SGP-001) is 10 times more accurate than the previous FSG-001. SGP-001 is only slightly 13.5 g, size 75x24x10 mm, connected the headphone jack, the Smartphone within seconds to a full radiation meter transform.
  • SGP-001 with 10 built-in semiconductor sensors now 10 times more sensitive With previous FSG-001, you can now also measure radioactive radiation in the air! Radiation measurement: gamma, X-ray - Measuring range: 0.05 ~ 200 mSv / h - Accuracy: < 15% - User interface: Smartphone (headphone jack) - Size: 75x24x9,9 mm - Weight: 13,5 g
  • FEATURE: practical, easy to carry, fast and accurate data, reasonable price, no battery needed, Personal EMF monitor for smartphone, easy and quick inspector. Compatible with smartphones: iOS 7.0, Andriod 4.3. Check before ordering if you can install "Smart Geiger Pro" app on your smartphone.
Radex RD1503 - Dosimeter (outdoor version) - High Accuracy Geiger Meter, Nuclear Radiation Detector
  • Outdoor edition
  • Combined detection of beta, gamma and X-ray radiation.
  • Detection range of 0.05 ~ 9.99 µSv/h (micro sieverts per hour) or millirems.
  • Audible alarm - Vibrator - Backlight.
GQ GMC-600 Plus Geiger counter detector Geiger counter detector Dosimeter Alpha Beta Gamma XRay LND 7317 sensor tube
  • High Sensitivity Pancake Geiger Tube lnd 7317 installed
  • Large LCD display - Auto source large horizontal and vertical display
  • Built-in flash memory and integrated WIFI
  • Real-time, Unlimited data logging, data logging data storage server
  • Rechargeable battery installed and many more...

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