Pocket radiation detector GMM 78 (Cracker)

For quick indication of ionising radiation. 

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GMM 78 (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 µSv/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.

Product references

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   µSv/h
Crunching from aprox. 1   µSv/h to aprox.  10   µSv/h
Buzzing over 10   µSv/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 230 g


Leaflet GMM 78  GMM_78-0.pdf 

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Pocket radiation detector GMM 78 (Cracker)