Top 7 Geiger Counters & How they work

Top 7 Geiger Counters & How they work

This article was written by Dave Robertson (see bio below). I asked him to write this knowing that I had little knowledge of Geiger Counters, but also knowing that I really wanted you guys to get solid basics and a decent comparison. I consider a Geiger counter a luxury item, unless you need it. Please keep in mind some of the recent (early 2016) articles in the news about documents stating that large amounts of radioactive material may have disappeared in the middle east. Of course we can’t say for sure what the who and why are, but we can say that dirty bombs are a very low tech way of causing large disruption once you have the material. Please keep in mind that you may need a Geiger counter to determine how radioactive your water supply or food might be. Even oceans can carry radioactive material as we saw from the recent nuclear disaster in Japan. Please don’t hesitate to add a Geiger counter or two to your bugout gear. John

What do they do?

A geiger counter is a device that detects radioactivity, also known as ionizing radiation. Nearly all geiger counters detect x-rays and gamma rays, the two strongest and most dangerous types of radiation. X-rays can travel long distances and can pass through most any material except lead. Gamma rays, though usually not as strong as x-rays, still require thick shields of lead or concrete to stop them. Both are very dangerous to the health of humans. Some geiger detectors also detect alpha and beta radiation. These types of radiation consist of particles produced by the decay of certain unstable atoms. These types of particles can only travel a short distance through the air and both can be stopped by heavy clothing or thick cardboard. Alpha particles can be dangerous, however, if ingested or inhaled.

Each geiger counter contains a small device called a Geiger-Muller sensor. It’s the thing that actually senses radiation. A pocket style geiger counter is roughly the size of a cell phone and stows easily in a pocket. You could walk down a city street, checking radiation levels as you go and nobody would be alarmed. The other type of geiger counter has an external wand and the sensor is contained in the wand. If you’re checking the radiation of specific objects, you’ll need to get the sensor close whether it’s the wand or the pocket unit itself. Most geiger counters show radiation levels with a visual readout and with an audible signal, a tick or click that sounds for each particle detected. The more noise the detector makes, the higher the concentration of radiation found. You’ve probably seen movies where characters use a geiger counter. A few random clicks might be acceptable, but when there is radiation danger the counter sounds like a radio emitting heavy static. Time to hightail it out of there.

Why do I need one? (Prepping for SHTF, TEOTWAWKI)

If a nuclear facility has a meltdown or a “containment problem”, you’ll want to know how it affects you. Also nuclear material is routinely mined, transported, and stored. What happens when there’s an accident? Are we always informed, or do problems happen without our knowledge? The authorities may be able to hide these problems, but if you have a geiger counter you can still be aware of the danger. Let’s say you find yourself in a situation where you need to bug out. Are there old uranium mines in the area? Recent hazardous spills? A geiger counter can help you stick to areas with lower radiation. It can also be used to test food, fish, and other game for high radiation levels. Even if there is no disaster situation, a geiger counter can be very useful. You may have items in your home that emit or contain low levels of radiation. Did you know that some antique pottery and furniture is coated with a radioactive glaze? Glow in the dark watch dials are usually slightly irradiated, smoke detectors contain a radioactive material called Americum (a tiny amount, but still). Are there unknown sources of radiation near your home or safe place? Get a geiger counter and check.

‘Normal” Radiation and what in the world is a microsievert?

People who measure radiation use various units of measurement. One is microsieverts/hour which is often shown as uSv/hr. You’ll also see it with a long tail on the left side of the “u”. That’s the technical symbol, but for those of us who can’t figure out how to make that fancy symbol on our keyboards, we just use uSv/hr. Sometimes you’ll see mcSv/hour which also stands for microsieverts/hour.

So how many microsieverts/hour is “normal”. Well, that’s a bit of a problem. No one seems to agree on what’s normal and “acceptable levels” as defined by the US government have changed several times over the years. But here’s one way to look at it. The average American is exposed to about 3600 microsieverts a year. That works out to about 10 per day, or .41 uSv/hour. If your geiger counter is showing .25 to .5 uSv/hr you know you’re pretty close to normal. Again, we all are receiving about 10 microsieverts per day. Consider that normal background radiation. For perspective, A dental x-ray adds 5 microsieverts. A flight from NY to LA exposes you to an additional 40 microsieverts. Spending one hour near the Chernobyl nuclear plant in 2010 would have netted you 6 sieverts, which is 6,000 microsieverts! Who knows what the level could be in a Teotwawki situation?



Another unit of measurement is milli-Roentgens/hour shown as mR/hr. In the US, Roentgens used to be the standard unit, but that is quickly being replaced by microsieverts which is the standard in much of the rest of the world. Most of the detectors you’ll find today still can be set to microsieverts or milli-Roentgens. Also, many radiation detectors will have audible, visual, or vibrational alarms that will go off when radiation levels are high. With most detectors you can set the level where you think “high” begins. 1.0 uSv/hour is considered by some to be “unsafe”, while 1.2 or more is considered “dangerous’. Again, there is no universal agreement on what constitutes unsafe or dangerous.

Geiger Counters Compared

Many of the most common radiation detectors I found are from four main companies: GQ, Radex, Soeks, and GCA. They are listed in order of price. The more expensive ones tend to have more functions and claim to be more sensitive and more accurate. All are calibrated from the factory and should be accurate out of the box. Some of the online reviews are helpful in determining the reliability and functionality of different units.

$99 – rating average on Amazon 4.2 stars (100 reviews) View on Amazon



This is a pocket sized geiger counter that has both audible and visual signals for detected radiation levels. Visual LED readouts show radiation detected in both microsieverts and milli-Roentgens. The device can continually monitor radiation levels and store the data in its internal memory. It can also be connected to a PC via the device’s USB port so that data can be stored and analyzed. It is powered by a rechargeable internal battery which can be charged using the supplied wall adapter. Continuous data monitoring is possible using the wall charger. An included disk provides software for use with a PC.

$147 -rating average on Amazon = 4.5 stars (84 reviews) View on Amazon



Pocket sized and operating on AAA batteries, the Radex is for use indoors, outdoors, and with objects. It has audio and visual readouts (in microsieverts and Roentgens) with audio and vibration alarms. The company claims the unit has been tested by the Japanese Consumer Protection Agency and it is backed by a one year warranty.

$174 -rating average on Amazon = 4.7 stars (17 reviews) View on Amazon



The Soeks Defender portable pocket size radiation detector includes 3.5 inch military grade Geiger Muller Tube SBM 20-1 that is the standard for surveying areas for potentially harmful ionizing radiation levels and for detecting radioactive contamination of food, packages, supplies, equipment and people after SHTF. The color display shows radioactivity levels in graphs and numbers and changes color to red for Dangerous Levels of radiation (greater than 1.2 uSv/hr) ,green for Normal radiation background measured less than 0.4 uSv/hr, yellow for HIGH radiation background 0.4-1.2 uSv/hr. Users can scroll through 3 menu categories: Device Settings, Measure and Radiation Dose; Users can easily set a threshold value, access Screen settings such as Brightness, Themes (4 possible), Off time, Sound (keypad, sensor and dose sound for the alarms and volume) Accumulated Dose. Accumulation process of radioactive dose begins after the device is switched ON and goes on permanently until device is switched off, regardless of current mode. When you turn it back ON, accumulation process continues; Battery life is 10 hours of continuos use batteries rechargeable through included USB cable or charger; Alarm sounds an audible alert when the measured radiation level exceeds safe level and can be turned off in settings. Designed by SOEKS and manufactured in Russia,

$260 – rating average on Amazon = 4.4 stars (17 reviews) View on Amazon

So what’s the difference between this unit and Radex’s lower cost RD1503? Whereas all the detectors mentioned so far have one Geiger-Muller sensor (that’s the thing that senses the radiation) this unit has two sensors. Like the other Radex unit, it has the same simple design with three buttons, LED display, and similar functions such as alarms, backlit display, and so on. It is covered by a one year (limited) warranty.

$288 – rating average on Amazon =4.0 (13 reviews) View on Amazon



This pocket size geiger counter is able to continuously monitor the radiation environment up to 999 days and work continuously up to 700 hours and alert a user if the preset dose and dose rate thresholds are exceeded. It measures bets, gamma, and x-ray radiation. This unit has two Geiger-Muller sensors, audible and visual alarms, and a color display. it has a USB port for connection to a PC and comes with 2 rechargeable batteries, an AC adaptor, and USB cable. It is covered by a two year warranty.

$350 – rating average on Amazon = 4 stars (22 reviews) View on Amazon



The GCA-07W is a professional quality monitor that can be certified accurate by the NCR, an independent licensing lab in the U.S. This radiation detector uses an external wand. The wand actually contains the Geiger-Muller sensor. This wand can then be more accurately aimed at radiation sources. Also, if you wish to monitor the radiation outdoors, you could project the wand outside and stay in relative safety indoors. It measures alpha, beta, x-ray, and gamma radiation. The Liquid Crystal Display shows levels in milli-Roentgens/hour or micro-sieverts/hour. The unit has both audio and visual indicators, a USB port to connect to a PC, plus headphone and power jacks. It uses a 9V battery for mobile operation but can be used with a wall adapter (included).

$595 – rating average on Amazon = 4.5 stars (33 reviews) View on Amazon



The Mazur Instruments unit detects alpha, beta, gamma, and x-ray radiation. The two-line, alphanumeric display supports both English and Japanese languagest. The display is backlit to support low-light conditions. Using only one key, users can scroll through several screens that display present, average, maximum and minimum measurements in uR/hr, mR/hr, uSv/hr, Counts per Second (CPS) or Counts per Minute (CPM). The PRM-9000 instrument not only records the maximum radiation measured, but also displays the time and date at which the maximum occurred. Battery life is over 4-years under normal conditions from a single 9-volt lithium battery. Standard alkaline 9-volt batteries available everywhere provide over 2-years of life under normal conditions. With over 100K bytes of data logging memory included, the PRM-9000 can autonomously store up to 91,466 minutes of time-stamped measurements. These measurements can then be uploaded to a PC in CSV format for analysis. A user-settable dose rate alarm sounds an audible alert when the measured radiation level exceeds that of the alarm level setting. Designed by Mazur Instruments and manufactured in the USA, the PRM-9000 includes abundant I/O options including support for headphones, external speakers, external power and PC/Mac USB data exchange (requires optional 3.5mm to USB adapter cable).



