All our meters are designed and assembled in the U.S.A
The EPA recommends prudent avoidance of EMFs - Make sure your home is safe!


USB-RAD121 Geiger Counter

Lowcost USB Geiger Counter!


Geiger Counter

The USB-RAD121 is a radiation detector that runs completely off your computer's USB port.  The device features a classic geiger counter click and light pulse for every count registered, while radiation levels are displayed on the computer.  The simple RadGraph software interface displays and graphs readings over time, and even allows the readings to be streamed to a personal webpage.

Make sure your home or office is safe from radiation by monitoring it with the USB-RAD121 geiger counter!

RadGraph Screenshot:

RadGraph Screenshot



  • Accuracy: ±10% Typical, ±15% Max (Co60)
  • Measures: BETA and GAMMA Radiation
  • Uses a high-quality American-made geiger tube
  • Range 0-50 mR/hr
  • Anti-Saturation: 500 mR/hr Minimum
  • Sensitivity: 450 cpm/mR/hr, dead-time compensated
  • Unit of Measurement: mR/hr, μR/hr, μSv/hr, CPM (compensated or uncompensated)
  • LED Flashes with each count
  • Buzzer beeps with each count (can be disabled in software)
  • Detector Window: 30 mg/cm2 x .002” thick
  • Interface: Computer, USB Type B (Cable Included)
  • Power: Port-Powered from USB Port
  • Unit Weight (without cable): 1.6 oz
  • Unit Dimensions: 4.00" x 1.25" x 1.00"
  • Connects to PC with USB Type A to Type B Cable (included)
  • Software Interface: RadGraph or RadMeter (both free downloads)
  • 2 Year Warranty
  • Made in the USA
  • HS Tariff Number for International Orders: 9030.10.00

Note: The USB-RAD121 is a calibrated geiger counter, designed for general purpose use and should not be used in safety-critical applications.

Code Examples

Yes, we even provide you with a C++ code example and class for reading the USB-RAD121 geiger counter!  The class allows you to connect to the device, take readings, convert your readings to mR/hr, and enable/disable the sound on the device.  The library provided runs on Windows, but it is possible to get the code to run on MacOS X or Linux as well.

#include <time.h>
#include "CUSB_RAD121.h"

void main()
    CUSB_RAD121 counter;
    double cpm, mR_hr;

    counter.Open();                                 // Connect to the device
    Sleep( 30000 );                                 // Give the unit 30 seconds to gather counts
    counter.GetReading( &cpm );                     // Get the counts per minute from the device
    mR_hr = CUSB_RAD121::Calculate_mRhr( cpm );     // Convert cpm to mR/hr
    counter.Close();                                // Disconnect from the device

Download the Visual Studio C++ example project, with the class source code here:

Visual Studio C++ Code Example (Example Date: May 4, 2013)


Product Reviews

"Very good quality device with all the attributes of modern technology.

I got the USB-RAD121. Everything was delivered in complete order and at the first touch you feel professionally designed and assembled unit.  Installation of device driver and software to 64-bit Windows 7 was easy and straightforward. GUI interface is quite complex, but has no perception of the screen cluttered with many symbols, buttons and windows." - Alexandre, Cambridge, New Zealand

Send your product reviews to This e-mail address is being protected from spambots. You need JavaScript enabled to view it

$ 219.00