Go Direct® Radiation Monitor (GDX-RAD)
Specifications and User Guide

Primary Test

  1. Connect the Radiation Monitor and start Graphical Analysis, Graphical Analysis Pro, or LabQuest App (LabQuest 2 or LabQuest 3 only).
  2. Verify that the Radiation Monitor is automatically identified.
  3. Place the Radiation Monitor near a radioactive source and collect data.
  4. Look at the LED, labeled αβγ, on the body of the Radiation Monitor – it will flash with each count; optionally turn on the audio signal to listen for counts. The total counts will accumulate in the data-collection software.

Tip 1: The Radiation Monitor measures total counts during the data-collection period, including any background radiation. A simple way to estimate the background radiation in your location is to run the Radiation Monitor without any radioactive source nearby for the same duration as your experimental trials. The total counts during that time interval will give you an idea of how much background radiation you can expect during each of your experimental trials.

Tip 2: Alpha particles interact easily with other matter and may be intercepted by the air between the source and the Radiation Monitor. If you are using an alpha source, be sure to place the Radiation Monitor within 1/4″ of the source. Likewise, alpha particles (and low energy beta particles and gamma radiation) do not have the energy to penetrate the plastic body of the Radiation Monitor. Place your source close to the wire screen at the end of the tube for the best reading.

What are the similarities and differences between radiation monitors?
How can you tell whether you have alpha, beta, or gamma radiation?
Can I monitor the radioactivity of red Fiestaware with your Radiation Monitor?
Where can I buy sources for nuclear radiation activities?

Sensor: LND 712 (or equivalent) halogen-quenched GM tube with a mica end window, 1.5 to 2.0 mg/cm2 thick
Gamma sensitivity: 18 cps/mR/he referenced to Co-60
Temperature range: -20-50˚C
Operating range: CPS 0-3,500
Shortest count interval: 20 milliseconds


If the sensor can be turned on when connected by USB but not when disconnected from USB, the battery either needs charging or has reached its end of life and can no longer hold a charge. First, try charging the sensor for several hours. If the sensor still won’t turn on when disconnected from USB, the battery has likely reached its end of life. If you intend to use this sensor wirelessly, the battery will need to be replaced. The rechargeable battery in this sensor is covered by a one year warranty but should last two to five years in typical use.

The GDX-RAD has a 5 year overall warranty, with a 1 year warranty on the GM tube. The GM tube has a finite life span, and it is normal that it must be replaced after a few years (although some tubes last much longer).
Tubes that fail within a year of purchase will be replaced under warranty.
Tubes that fail after a year will be replaced for a fixed fee of $89.
Tubes that are punctured will not be replaced under warranty.

Nuclear Radiation with Vernier (NRV, discontinued)
Vernier Radiation Monitor (VRM-BTD)