Expanded and combined uncertainty in measurements by GM counters

This paper deals with possible ways of obtaining expanded and combined uncertainty in measurements for four types of GM counters with a same counter’s tube, in cases when the contributors of these uncertainties are cosmic background radiation and induced overvoltage phenomena. Nowadays, as a consequence of electromagnetic radiation, the latter phenomenon is especially marked in urban environments. Based on experimental results obtained, it has been established that the uncertainties of an influenced random variable ′number of pulses from background radiation′ and ′number of pulses induced by overvoltage′ depend on the technological solution of the counter’s reading system and contribute in different ways to the expanded and combined uncertainty in measurements of the applied types of GM counters.