| T O P I C R E V I E W |
| hannaconner |
Posted - 07/07/2025 : 00:44:30
Hi All
I bought GC-500 last year and yesterday also Radiacode 103G which was about 5x more expensive than GC-500.
I noticed that GC-500 readings in CPM are significantly different (lower) compare to Radiacode 103G which shows about 60x higher! I assume that GC-500 has a bug in calculation of CPM as it actually shows CPS (Counts Per Second) and not CPM (Counts Per Minute). Attached comparison photo. At the beginning I suspected that something is wrong with my GC-500 as it says that it has M4011 tube, but mine has J321? Has anyone noticed this, is my GC-500 I bought on Amazon.de counterfeit product? I attached photos.
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| 1 L A T E S T R E P L I E S (Newest First) |
| EmfDev |
Posted - 07/07/2025 : 13:32:03
The RadiaCode 103G, like many compact radiation detectors using silicon photomultipliers (SiPMs) or similar solid-state sensors, may indeed show higher CPM (counts per minute) values compared to Geiger-Müller (GM) tube-based devices. But that doesnt necessarily mean its detecting 60× more gamma radiation in reality. Heres why:
Possible Reasons for High CPM Readings in the 103G:
Multiple Small Detectors
The 103G uses an array of small light detectors and scintillator material (e.g., CsI(Tl)). These can be highly sensitive and fast, but if the system lacks proper shielding or background rejection, it may pick up more environmental noise or low-energy photons, inflating the CPM. Or a gamma particle just produces too many photons.
CPM vs µSv/h Conversion Differences
A device showing 10,000 CPM doesn’t automatically imply high dose unless the calibration factor justifies it. The 103G may simply report CPM with more granularity, but its µSv/h reading is what should be compared across devices for actual dose rate.
Physical Limitations
Detecting 60× more gamma in the same physical space would require:
A significantly larger or more efficient scintillator
Better photon collection optics
Extremely low noise electronics
While the 103G may be more efficient than a GM tube in some energy ranges, a true 60× improvement for gamma detection in such a compact device is unlikely without trade-offs in precision, selectivity, or false positives.
Youre right to be skeptical. The CPM count can be misleading if viewed in isolation. Its likely that:
The 103G is very sensitive, possibly to a fault (overreporting background),
It shows more raw events, but not necessarily more meaningful gamma dose,
The dose rate (µSv/h) is a better metric for cross-device comparison.
If youre comparing with another device (e.g., GMC-600+ or RADEX), focus on the µSv/h readings, not just CPM. |
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