Monitor 4 Geiger Counter


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2.00 LBS
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m4casetn.jpgThe Monitor 4 detects Alpha, Beta, Gamma, and X-radiations. It also offers 3 operating ranges, a battery check feature, and includes a padded carrying case (right) with belt clip.

m4panel.jpgA red count light flashes with rising radiation levels, along with an audible click which can be switched off for silent operation (see photo at left).

Radioactivity also registers on a dual scale analog meter adjustable for 3 operating ranges up to 50 mR/hr or 50,000 CPM (see photo below right).

Play this sound file to hear the audible clicks of  the Monitor 4, recording 3 different tones, depending on which of the 3 operating ranges is set.mrhr.jpg


In addition to detecting X, Gamma, and Beta radiation, the Monitor 4 is capable of detecting  Alpha radiation by virtue of a thin mica window at the end of the Geiger-Mueller tube.  It is located strategically at the top of the instrument which,  combined with the ergonomic enclosure design, makes aiming the unit at a specific source for Alpha detection that much easier.  See photo at left.m4windowtn.jpg

This unit also has a Data Output port to record counts on a computer or data logger, as shown in the picture at right.  Click on this link for more on the on data output, and the optional Software accessories.m4dataport.jpg

The Monitor 4 runs on a single 9 volt alkaline battery (included) which will last up to three months on continuous use at background levels.

The Monitor 4 is an excellent all-around Pocket Geiger Counter.  The switchable operating range is an especially nice feature if you are dealing with low levels of radioactivity - you can set it to the most sensitive operating range so the meter is easier to read, i.e. the needle will "jump" that much farther for the same level of radioactivity.

usvhr.jpgFor the same price, the Monitor 4 is also available in a dual-scale meter that reads in µSv/hr (in lieu of CPM), in addition to mR/hr (see picture).  Readouts in µSv/hr are more popular in Canada and overseas.  So please specify which meter configuration you wish to order.

This item typically ships within 1 business day.m4-response-curve.gif

Specifications for the Monitor 4 Geiger Counter:  


Halogen-quenched, uncompensated Geiger-Mueller tube with thin mica end window

Window Size

1.5 to 2.0 mg/cm² thick; effective diameter is .360”

Radiation Detected Alpha, Beta, Gamma, X-ray


Detects alpha down to 2.5 MeV; efficiency at 3.6 MeV > 80%


Detects beta at 50 keV w/35% efficiency, at 150 keV w/75%

Detects gamma and X rays down to 10 keV thru window, 40 keV minimum through case; gamma sensitivity is 1,000 CPM/mR/hr


± 10% of full scale, referenced to Cs-137

Operating Ranges

0-.5, 0-5, 0-50 mR/hr. and 0-500, 0-5,000, 0-50,000 CPM

Optional Meter Range 0-.5, 0-5, 0-50 mR/hr. and 0-5, 0-50, and 0-500 µSv/hr.


At factory to NBS standard Cesium 137 gamma source


Holds full scale in fields as high as 100X maximum reading

Power Required

One 9-volt alkaline battery (included in price of the unit)

Battery Life

Up to 2,000 hours use at normal background levels

Temperature Range

- 20° to + 55° C (- 4° to + 131° F)


215 grams (7.6 oz.) with battery


206 x 71 x 48 mm (8.1 x 2.8 x 1.9 in.)


LED indicator, internally mounted audible beeper for count rate

Warranty One year limited, includes CE mark

Country of Make


Click on this link for the Operating Manual for the Monitor 4 and Monitor 4EC 


2 Reviews Hide Reviews Show Reviews

  • 4
    Awesome counter

    Posted by Ray37212 on Mar 21st 2018

    The Monitor 4 works very well stand alone or on the GeigerNetwork. The only con is that there is no external power connection so I bought rechargeable batteries.

  • 4
    Great portable unit

    Posted by Ray on Mar 11th 2018

    Works well and has good battery life. The down side is that it does not have an external power jack so it always runs on batteries. I also have a 2007 model that still works!