A few years back, I built a geiger counter from a popular kit to get to know more about radiation. In order to do some online baselining of background radiation, I implemented an edge detector on an mbed (NXP LPC1768) microcontroller that will count the pulses, create an average (counts per minute, CPM), and upload the data to Xively. I also added a BMP085 temperature and air pressure sensor in order to graph the current temperature and barometric pressure.
The setup looks quite prototype-ish as it mainly consists of a lot of jumper wires on a breadboard, but it's been working well for over a year at my former flat. So today, I installed the kit in the lab's 19' rack, graphing vital information about the general climate (temperature, pressure and hard gamma rays) at FabLab Zurich.
Please don't fiddle around with the kit too much as the wires will come off easily. Also, please don't bring fissionable material to the lab since it will mess up the background radiation measurements besides being a general health risk.
You can find the current measurements (updated every minute) as well as three months worth of graphs here.
While normal background radiation should average somewhere between 20 and 30 CPM, I’m currently seeing sporadic measurements up to 400 CPM, which I cannot explain right now. Will investigate this further.
Ich konnte mit meinem Geigerzähler keine Strahlung im Lab finden 🙂
(Zumindest keine zum Zeitpunkt der Messung)
Indeed, it seems I was overloading the HV part of the counter, causing sporadic avalanche effects in the geiger tube.
Lowering the voltage on the tube to the recommended seems to have fixed this, so the measurements are now accurate.