How to Use It
Easy — turn on the switch and listen for clicks! And watch the LED: it will flash every time a beta particle or gamma ray hits the tube!
NOTE: The tube that comes with this kit is not sensitive to alpha particles. However, the kit is compatible with other tubes that do detect alpha.
Mute: If you get tired of hearing the clicks, you can push the button S2 to mute the sound.
Pulse connector: The pulse connector (J6) has the following pinout:
1. VCC (nominally 3V)
2. Pulse output — a short (100µs) active high pulse every time the Geiger tube fires
For more information, design files, source code: mightyohm.com/geiger
To connect your computer to the serial port (J7), you'll need a USB-serial converter that operates at 3.3V TTL levels. The serial header is set up to work with the common FTDI-232R-3V3 serial cable.
Data is sent over the serial port at 9600 baud, 8N1. The data is reported in comma separated value (CSV) format:
CPS, #####, CPM, #####, uSv/hr, ###.##, SLOW|FAST|INST
There are three modes. Normally, the sample period is LONG_PERIOD (default 60 seconds). This is SLOW averaging mode. If the last 5 measured counts exceed a preset threshold, the sample period switches to SHORT_PERIOD seconds (default 5 seconds). This is FAST mode, and is more responsive but less accurate. Finally, if CPS > 255, we report CPS*60 and switch to INST mode, since we can't store data in the (8-bit) sample buffer.