Simulation mode for the Geiger Counter

While obtaining samples of materials radioactive above background is not an easy task (fortunately for the sake of human health), I had to find a way of testing the dose measurement algorithm in a different way. As I have explained in a previous post, the device is divided in two modules: a UI module, and the detector device. Each has its own digital logic, and communicate with each other through an I2C bus. As such creating a simulation mode would be a simple mather of programming a new function in the detector that would allow randomly spaced pulses to be generated, instead of being triggered by the Geiger tube. This have been done simply by using the Atmel standard libraries random() function. Using the interrupt generated by the watchdog timer overflow, the following code is executed periodically:

LENA - Now featuring dose measurement

The DOSE feature discussed in the previous post is now done. Taking into account the GM tube characteristics, a realistic measure of radiation dose in uSv/hour is now being calculated, based on the single event rate. From the information obtained on the internet regarding the SI-39G tube, the value of 0.00049 uSv per pulse was taken into account for the calculation of the dose.

Additionally, another mode usually found in most Geiger counters and dosimeters is the CPM (Counts Per Minute) mode. It provides a relative measure (that is of course GM tube dependent) of the radiation exposure, based on the ammount of particles detected by the tube. In this case these can be either Beta particles with more penetrating energy, and Gamma photons. Alpha particles cannot be detected by this particular tube (the SI-39G).

LENA - The Geiger Counter that was finally made portable!

With the Geiger Muller tube module having been posted in a previous post, namely here, another important development was missing. While fully functional at that time as a sensor device which could readily be interfaced with via I2C, or having the pulses be directly picked up via a dedicated TTL signal, by itself the device could not be carried on the field and be expected to operate without additional hardware.

I2C Geiger Counter

With nuke plants operating under questionable technical safety, natural events threatening humans and their dangerous energy production artifacts, and other humans disseminating fear through nuclear sovereignty upon the rest of the world, we came a long way from the happy ignorance of distant decades.