POCKET RADIATION DETECTOR GMM 78 (CRACKER)
“Cracker” is pocket detector for ionising radiation. It is used for quick indication of radioactivity. As a detector, cylindrical thin-wall Geiger Mueller tube is used. Each pulse caused by a passing photon is heard as crunching coming from the built-in loudspeaker. At the background radiation (aprox. 100 nSv/h), about 10 cracks per minute are heard. To the dose rate of aprox. 10 ?Sv/h, cracking sound is heard, which, at the dose rates higher than that changes into a buzzing sound which faints at higher dose rates.
Energy source for the instrument is built-in battery that can provide power continuously for 100 hours. For changing the battery, back cover of the instrument must be removed. With almost empty batteries, sound becomes weaker.
Technical data:
| Detector | cylindrical halogen Geiger Mueller tube type SBM 20 |
| High voltage | 400 V |
| Background | aprox. 10 imp/min (100 nSv/h) |
| Cracking | to aprox. 1 ?Sv/h |
| Crunching | from aprox. 1 ?Sv/h to aprox. 10 ?Sv/h |
| Buzzing | over 10 ?Sv/h |
| Limit of use | aprox. 1 Sv/h |
| Power supply | battery, 9V |
| Dimensions | 135 x 60 x 30 mm (L x W x H) |
| Mass | 230g |
