All that’s required to measure radiation is a simple PIN photodiode and a suitable preamplifier circuit. We present here an optimised preamplifier and a microcontroller-based counter. The microcontroller takes care of measuring time and pulse rate, displaying the result in counts per minute.
This device can be used with different sensors to measure gamma and alpha radiation. It is particularly suitable for long-term measurements and for examining weakly radioactive samples. The photodiode has a smaller sensitive area than a Geiger-Müller tube and so has a lower background count rate, which in turn means that the radiation from a small sample is easier to detect against the background. A further advantage of a semiconductor sensor is that is offers the possibility of measuring the energy of each particle, allowing a more detailed investigation of the characteristics of a sample. The optional PC-based software displays the energy spectrum, permitting a very detailed analysis to be carried out.