This is the smalles geiger tube I could find. It’s so cute but… so insensitive to the background. It’s a good tube to build around it a personal dosimeter. It’s not suitable to monitor background radiation.
Tech. spec.: ·Radiation determine: beta soft/hard; gamma ·Voltage of start of counting: 260V - 320V; ·Operating voltage (recommended): 380 - 420V; ·Length of flat part of counting curve (plateau): 100 V ·Slope of the counting data: < 0.15%/V; ·Own background: < 0.2 imp/s; ·Max. counting range: 650 imp/s; ·Sensetivity: 6.5 - 9.5 imp/uR standard 137Cs, p = 10 uR/s; ·Working temperature range: -50…+60 C ·Weight: 0,8g. ·Dimensions: counter length 21mm, diameter 6mm