Demo of the Eberline E520 with both the internal and HP-270 beta/gamma probes plus SK-1 speaker.

This is a fantastic unit which was manufactured in the early 90s. I calibrated it using a pulse rate generator, and did a very slight adjustment on the x1 and x10 scales. While I don’t usually recommend used equipment like this for professional use, this does exceed the NRC standard for calibration of instruments to be used at fuel processing, reactor, industrial radiography, well logging, and many other regulated applications. There’s no reason that this unit can’t be used professionally!
The .01x to 10x scales were also done using a calibrated Cs137 source. The x100 scale, which uses the internal probe, required a very high impedance probe set to calibrate; it was spot on and needed no adjustment.
The E520 is the one piece of equipment you’d want to have in the case of nuclear accidents or detonation of nuclear weapons, as it goes up to 2 Roentgens per hour, whereas most Geiger counters only go up from 50-200 milliRoentgens per hour, or up to just 1/10 of what this counter goes up to.
In disastrous situations, you can get a rough reading of gamma dose if the meter is pegged beyond 2R/hour by listening to audible feedback from the SK-1 speaker, which has a brand new 15 volt battery that is expected to last several thousand hours. I have seen several units with good batteries that were installed in the early 90s, so this should last you a very long time.
The E520 can be used with other GM probes like the HP-260/210 pancake and HP-190 end window alpha/beta/gamma probe, but it is specifically designed to be paired with the HP-270 for dosimetry. The meter face reads in mR/hour and counts per minute; the mR/hour scale is only valid when using the included HP-270 probe. It is not designed to use scintillation or proportional probes, and has a fixed voltage specifically for use with 500-900 Volt GM probes.
This unit is excellent for uranium and thorium mineral hunting, and this is one of the counters that I give to friends when we go to closed mines or tailing piles in search of hot rocks. This unit has never failed in over two decades of use, and two D batteries last a very long time; I’d estimate a solid 200-250 hours of use based on experience with this specific unit.
If you’re a doomsday prepper, this is the one you want. There is no other commonly available Geiger counter, with the exception of the Bicron Surveyor 2,000 and one Ludlum model which uses an internal probe only, which gives you such an extremely high dose rate measurement. And the Bicron 2000s are overpriced with fewer features.
I was surprised to find a small beta window on the internal probe! If you pop it out of its case, I can be used to determine beta/gamma combined if the source is placed directly in front of the small beta window, or if you remove the internal LND GM tube from its housing, as shown in the video.
This is the last E520 I own, and I have a lot of fond memories with it. The SK-1 speaker puts out a classic and distinctive sound, and is a fairly complex bit of machinery on its own; containing several resistors and capacitors to operate independently from the E520. In other words, you can use this speaker effectively with the BNC output jack on your favorite meter or scaler because it has circuitry independent of the unit…
Speakers usually rely on internal circuitry of a counter. I use one for audible feedback on an Eberline SAM-2, which has no built in audio, but is modified to have a scaler output jack. It can also be used with any other counter or scaler that has BNC output.
This unit comes with a very high quality stock BNC cable, which along with the speaker, will already be connected and ready for use right out of the box. I am a bit saddened to let this one go, but I have plenty of high range equipment and despite my desire to have such a solid and high range counter, simply can not justify keeping it.
The E520 is very well built, and has an excellent reputation as a meter which lasts forever. The only part I’ve ever seen go bad on one of these is the voltage regulator, and this units voltage regulator is just fine; there are no buzzes or hums from the transformer, and I sincerely believe that this unit will continue to serve its owner for decades without any problems.
It has gone for decades without needing adjustment during calibration. This unit was within specifications on the “as found” check, but the adjustments made brought it from within a 10% variance range to about 2 or 3%; not even noticeable. Therefore, it is highly accurate, and the specifications of the included HP-270 probe are all over the internet.
I also like this counter because it has a 0.01x range, allowing you to measure very low levels and background radiation. I can’t say enough good things about this model. This one is in good physical condition and flawless electronic condition. An autunite specimen in a lead pig is available free of charge, if you want it. I used to sell processed and filtered autunite samples for 65 bucks on eBay!