S.E.I Radiation Alert Inspector Geiger Counter

Product Name:Radiation Alert Inspector USB Handheld Digital Radiation Detector with LCD Display
Brand:Radiation Alert
S.E.I Radiation Alert Inspector Geiger Counter
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For the past several years the S.E. International Alert Inspector was our top rated Geiger counter. While this year it’s slipped to the #2 position, it’s still an excellent detector that’s head and shoulders above most of its competition and remains one of the most popular portable Geiger counters ever built.


One of the few detectors still manufactured in the U.S., the Inspector offers great performance in a rugged field tested case. It can detect alpha, beta, gamma and x-rays and includes a backlit 4-digit liquid crystal display that indicates readings in your choice of counts per minute, mR/hr, counts per second, uSv/hr or accumulated counts. The digital readouts are highlighted with a red count light and beeper sound for each count detected. Other features include configurable alerts, external calibration controls and an adjustable timer.


Unlike other Geiger counters with board mounted tube, the Inspector uses an external halogen quenched Geiger-Müller tube with a thin mica window 1.75″ across. It detects alpha particles down to 2 MeV, Beta to .16 MeV and Gamma to 10 KeV.


User configurable alerts can be set for µSv, mR, and CPM, and are audible in the Timer Mode when the programmed alarm threshold is reached. The display updates every 3 seconds, with each update being a 30 second rolling average at ambient background. This average time period decreases as the radiation level increases.


Operating life with one 9 volt alkaline battery is an impressive 2160 hours. The internal memory is able to store 1356 data points, which works out to 226 hours (9+ days) at 10 minute intervals and 1356 hours (56+ days) at one hour intervals. The device has a standard mini USB plug and can be connected to a Win/Mac for data download to proprietary software.

S.E.I. Inspector Geiger Counter

Current Specification Summary


Detection Profile —

Halogen-quenched, uncompensated GM tube with thin mica window, 1.4-2.0 mg/cm2 area density.
Effective diameter 45 mm (1.77 in.).
Alarm: mR/hr .001 – 50 and CPM 1 – 160,000. 70db @ 1m. Pulsating beeper.
Radiation Detected: Alpha, Beta, Gamma, X-ray
Operating Range:
mR/hr – .001 (1μR) to 100 CPM – 0 to 350,000
μSv/hr – .01 to 1000 CPS – 0 to 5000
Total/Timer – 1 to 9,999,000 counts
mR/hr ±10% typical (NIST), ±15% max – 0 to 100
μSv/hr ±10% typical (NIST), ±15% max – 01 – 1000
CPM ±10% typical (NIST), ±15% max – 0 to 350,000
Alpha to 2 MeV.
Beta to16 MeV;
Gamma to 10 KeV


Internal Data Logging —

Set in included USB Observer Software
Default internal memory 10 minutes.
Stored in a text delimited file.
Interface to computer, data logger, or other device.


User Interface —

Languages: English
Display: The LCD shows various indicators according to the mode setting, function(s) being performed, and battery condition
4 digit liquid crystal display with indicators. Display updates every 3 seconds.
Count Light  Red LED flashes with each radiation event.
Audio Indicator Internally mounted beeper (can be switched off for silent operation)
I/O Ports: Dual miniature jack drives CMOS or TTL devices and counts to computer or data logger.
USB for use with Observer USB Software for PCs
Power: Alkaline battery 9-volt. Battery life is ca. 2000 hrs.
Temperature Range: -10ºC to 50ºC (14ºF to 122ºF)
Weight:  273 g (9.6 oz.) without battery
Dimensions: 150 x 80 x 30 mm (5.9 x 3.1 x 1.2 in.).
Warranty: 1 year limited warranty. 90 day limited on GM Tube


Suggestions for Improvement

My major complaint is larger form factor. The unit has not been redesigned in many years and looks a bit clunky and primitive when compared with the newer European models. I also think it’s about time to add some more firmware enhancements to display data in multiple formats.



Accurate external probe
2160 hours on single battery
Easy data logging and upload
Dual 3.5mm audio and USB ports
Detects alpha, beta, gamma, and x-rays.



Oversize form factor could be reduced
Sensitive to high temperatures



The S.E.I. Alert Inspector is a Geiger Counter for both the serious hobbyist or security minded professional who needs accurate and reliable radiation detection at home or in the field. It offers enough professional features combined with simple operation to fit nicely in the market niche of high-end consumer or low-end professional applications. At $450+, you can’t go wrong with the Alert Inspector.


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