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Description: The Type 5 Pocket Geiger Radiation Sensor from Radiation Watch is a highly sensitive radiation sensor designed for the embedded systems market. Capable of detecting Gamma and Beta radiation, this sensor has a simple pulsed output that can be used with any microcontroller. Radiation Watch has a handful of documents and example Arduino code to get you up and running. They have also written a Windows example program in C# (source included!) to output graphs to a computer using an Arduino as the reader.

These small Geiger sensors feature a measurement range of 0.05uSv/h to 10mSv/h at 0.01cpm to 300Kcpm with a required measurement time of two minutes. The Pocket Geiger has an onboard DC boost circuit, so the board can be supplied with a friendly 3V to 9V. Using only 30mW (10mA @ 3V), it is very low power. Additionally, the counter comes with an optional enclosure and 3.5mm cable.

Note: This product is for educational purposes and should not be directly relied upon for determinations regarding one’s health or safety.

Dimensions: 58 x 26 x 11mm

Product Includes:

  • Type5 Geiger Sensor board with copper EM shielding
  • Brass plates (attach to block beta particles)
  • 16” TRRS cable
  • Plastic enclosure
  • Extra 3.5mm TRRS jack


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Customer Comments

  • An Arduino library is available if you go to the Library Manager in the Arduino IDE and search for “RadiationWatch”. This library is also available here: (disclosure: I worked on the original version of this library which was derived from the sample code).

  • This is one of my favorite sensors.

    Here’s an open driver:

    The Arducorder mini, a handheld multisensor device, that includes a backpack board to make the Radiation Watch Type 5 more sensitive. Some of the posts also show histograms of pulse widths from this sensor, that appear to contain some energy-level information:

    OpenCT, an extremely low resolution scanner using this sensor and a radioisotope source:

  • I like this sensor. Appears to work well with Arduino - particularly with interrupt based counter. The pulse width seems to encode photon energy. Calibrating now but initially matches background radiation.

  • So glad I got the email for this. The First Sensor pin diode is extremely accurate. I’ve tested it against an industrial gamma detector with a Cesium-137 source and they are very close.

  • A little disappointing straight out of the box…the incredibly long response time, using the included Arduino sketch, makes the sensor basically useless.

    I have a small chunk of uranium ore to use for testing radiation detectors. It takes this sensor ~2.5 minutes to respond to the ore, slowly coming up from (about) the 3 cpm background to 600 cpm ore count. Likewise, when the sample is removed, it takes another 2.5 minutes to settle back to the background 3 cpm. I’m thinking the included sketch needs some work…

    Also, the companion Windows C# program, PokegaMonitor, is limited. It only allows communications on serial COM1 through COM9. You’ll have to edit and recompile the code to get it to work at other ports above COM9, like mine at COM11. Even at that, it has a very limited range - the ore sample sends it off the chart.

  • I’m curious what people are seeing for background CPM, and what samples people have found interesting when using this device? (I’m seeing about 3 CPM currently and am considering getting the Geiger test card from United Nuclear…)

  • I’m trying to understand the schematic. Can anyone point me to a data sheet for U4, which the schematic says is an LT1651? My search skills have come up short.

  • How durable is this sensor? Is this sensor durable enough for used on weather balloons or drones?

    • I plan to fly it on rockets and possibly balloons above 100k'.

      I suspect will see noise on rocket flight during motor burn. But expect should work well during coast, at apogee and during descent.

    • why send it in the sky? want to read high levels of radiation (radon) put it in your basement, you’ll be surprised - depending on where you live in the country, but should still pick it up. When radon decays it emits a beta particle and gamma ray so should be picked up by this sensor if my thinking is correct.

    • It’s measurements tend not to be accurate when it’s being vibrated (that’s what the “NS”, or noise pin is for, though it does not appear to pick up all vibrations that affect the sensor). I’ve had one on a handheld device for 2 years and it’s still working well (though it isn’t in environmentally challenging applications like weather balloons that probably require it to be in a complete sealed enclosure)

  • Hmm, to my knowledge the Type5 version cannot simply be connected to the phone via jack as stated in the video: But perhaps I am wrong?

    • Pls check my sketch, Type5 -> 3.5mm phone plug (MIC), thanks!

    • Agreed, only the type 4 can be connected to a phone via a TRRS jack and even then supposedly only to certain iPhones or iPads:

Customer Reviews

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Unable to get it to work.

The Sparkfun write up says the pocket geiger can be connected to mobile phones and used with a downloaded app. It didn’t work with my Samsung Galaxy S7 Edge.

Spark fun Tech Support confirmed it didn’t work with their Galaxy S5 or iPhone 6, and suggested that I could build a small interface and power supply circuit, which they said worked great on the iPhone 6, and sort of worked for their Galaxy S5. I explained that I wasn’t looking for a new project, just a sensor that worked. I returned it.

Yeah unfortunately it only works with some phones. We’re unable to confirm its compatibility with all types of phones.