• Radiation Detectors

Old, vintage Geiger counters are a lot of fun. Not only they are built like tanks but also have a certain character and feel to them. Unfortunately, the calibration on them might be a bit off as a result of their ageing components. Today I want to show you how you can easily calibrate your Geiger counter so that it shows accurate readings again!

In order to do this you will need:

• a multimeter with 2 probes and a 1G Ohm (1000M Ohm) resistor for measuring the HV
• a pulser
• and your Geiger counter with a cable to connect a GM probe

Firstly, you will need to check if the voltage on your meter if it is correct using a multimeter and a 1G Ohm resistor. I already made a post about it which you can find HERE.

The next step is to connect the pulser in place of the probe. Pulser will generate “clicks” at a consistent rate which will allow us to calibrate the meter. I personally use one made by GEOelectronics and I highly recommend it but others should also work fine.

Now turn on your meter and set your pulser to generate a desired amount of CPM. Make sure that the needle on the meter is showing the correct amount of CPM generated by the pulser on every scale. If it is not, then adjust the calibration potentiometer until it sits right where you want it.

If your meter uses dose units such as uSv/h, then you will need to find a conversion rate from CPM to uSv/h for the Geiger tube used in your meter. THIS post by DIYGeiger covers most of the GM tubes commonly used and gives a rough conversion ratio from CPM to uSv/h. Please note that this isn’t very accurate and if possible, you should use CPM when measuring activity of a samples. Dose units work only when the meter is calibrated to the specific isotope which is being measured. In other cases, the readings can be lower or higher than in reality.

Congratulations, you have now successfully calibrated your Geiger counter! However if you are a professional and you want the most accurate calibration on your meter, then you should most probably send your meter for calibration to a professional lab but for most hobbyists, this method should be more than enough!

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Recently, I have acquired an Eberline 120 survey meter however since it is pretty old, I was a little bit worried that the voltage coming from the unit might be too high for the probe due to the age of the internal components so I decided to measure it just to be sure.

Unfortunately, if you are going to measure the voltage using a cheap multimeter, you won’t get an accurate reading. That is because the impedance on the multimeter is different from the one on the Geiger counter. An easy way to fix this issue is simply to add a 1G Ohm (1000M Ohm) resistor between the positive probe and the Geiger counter.

Now simply set the multimeter to the 2000mV and connect probes to the BNC connector on the Geiger counter. The number on the display of the multimeter shows the voltage coming from the Geiger counter.

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Since I have a lot of Geiger counters, I have decided to make my own probe with a 1G Ohm resistor built into it. Whenever I want to measure the voltage in my meters I can quickly change the standard probe for my moded one!

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Here is another great post on this topic:

https://ea4eoz.blogspot.com/2012/09/one-gigaohm-high-voltage-probe.html?fbclid=IwAR35wkE80V-yRVkkodyz_Gpa6DZnuyyPXcLMwAthdo9z8kKJjrWDpUucpsY

Today I want t show you a device that allows you to do gamma spectroscopy on the go! Let’s take a closer look at the RAYSID Gamma spectrometer.

RAYSID is a gamma compensated dosimeter, gamma spectrometer and radiation mapping/logging device all in one small package. There are 4 models with the cheapest being 300 euros and the most expensive being 600 euros. All of them have exactly the same features with the only difference being the value of the FWHM which is important only when doing gamma spectroscopy. So if you are not interested in doing gamma spectroscopy then you will be perfectly satisfied with the cheapest model but if you would like to do gamma spectroscopy then I would suggest you invest in the slightly more expensive model.

In terms of size, RAYSID is comparable to a Zippo lighter and weighs only 65 grams. Inside there is a rechargeable battery that lasts for over 10 days on a single charge. The heart of this device is a 5 cm3 Thallium activated Caesium Iodide (CsI(Tl)) scintillation crystal.

Inside the box, there is a manual, USB charging cable, caring case, selfie stick with a holder for RAYSID and RAYSID itself.

In order to use the RAYSID

to its fullest potential, it is best to connect it with RAYSID app. Unfortunately, the RAYSID app does NOT work with iOS and is only compatible with android 5.0 (or higher) devices.

In order to turn the unit on, we simply need to press the power button. Next, we can open the RAYSID app and connect RAYSID with our phone. In order to turn on/off the speaker simply press the power button once. To turn the unit off press and hold the power button.

Search mode

Search mode is useful when searching for radioactive hot spots. The upper side of the screen displays a graph showing current CPS and the dose while the lower side shows the rough gamma spectrum which is updated in real-time.

On the right side, there is a set of icons. The first one locks the display in the current position (vertical or horizontal). The camera icon allows you to take a photo with the current measurements.

Gamma Spectroscopy

One of the best features of RAYSID must be its ability to do gamma spectroscopy. Depending on the model, FWHM varies from >15% to <8.5%*. The smaller the FWHM the more accurate and narrow peaks. For the best result, it is best to have FWHM below 10%.

As of right now, the spectrum range is from 25 keV to 1000 keV which means you should be able to identify the most common radioactive isotopes such as U-238, Th-232, I-131 or Cs-137. In a future update, the range will be extended to 3000 keV allowing for the identification of radioactive isotopes such as K-40 or Co-60.

Another great feature is that RAYSID has a temperature compensation which results in the spectrum not being affected by the weather (in extreme cold or heat, spectrum mode is unavailable). Manual calibration can be done in the “settings” tab.

What I really like is that when doing a gamma spectrum, the app automatically identifies different isotopes based on their energy peaks which means you don’t need to analyse the spectrum to identify the isotope you are measuring. The average dose and CPS are also displayed.

It is also possible to save the background spectrum which helps visually to see any minor differences when measuring samples for a trace amount of radioactive contamination. In order to do that simply click on the “BG” icon with a “download” arrow. This will save the current spectrum as background. You can toggle on and off the background spectrum by pressing the “BG” icon.

Triple pressing the power button will restart the spectrum

*FWHM measured at 662 keV

Map

Since RAYSID is so small, it is very portable and you can take it anywhere you want. What is even better is that it automatically makes a map of background radiation anywhere you go! You can set the map to show background dose (uSv/h, uR/h) or background activity (CPS, CPM and Bq/m2 (only for Cs137)).

To enable global map press the “web” icon. If you wish to share your map with RAYSID global map than press “share” icon. If you want to delete point on the map click the “bin” icon and hover the red square over the points you want to delete

You can have a look at the current state of the map by clicking HERE

Alarm & Log

A CPS or dose alarm can be set in the “setting” tab. When an alarm is trigger, it will be logged in the “Log” tab. Double pressing the power button will turn the alarm on or off.

Conclusion

I personally think that RAYSID is the best device of its kind. Relatively low price and very good performance make it one of my favourite radiation detectors in my collection and since it is so portable, I take it everywhere with me! So if you are in the market for a portable gamma spectrometer I highly recommend the RAYSID.

Gamma-Scout is an iconic Geiger counter but is it any good? Let’s find out!

Before I start, I must say that the unit that I got is not stock. It has a new battery and the GM tube was swapped for Philips ZP1400 since the original Ludlum LND712 was broken. Lastly, I have also added a metal mesh in front of the GM tube for some additional protection when measuring alpha radiation.

The version I got is the Standard model which retails for around 380 euros. Gamma-Scout offer three other models. Alert model which has an audible clicking sound and a settable alarm, a rechargeable model that has a rechargeable battery and an Online model which allows user to connect the Geiger counter to PC wirelessly.

Despite the fact, the GM tube was not original, the results I got were fairly similar to my other Geiger counters which meant that Philips ZP1400 is a very good alternative to the LND712.

One small design issue that I noticed with the Gamma-Scout is that the GM tube is slightly pushed back into the meter. This means that detecting alpha particles will be more difficult since they have a very small range.

What I really like about this meter is that it can detect alpha, beta, gamma radiation and it shows readings in dose units as well as raw activity (CPS).

Unlike most electronic devices, Gamma-Scout has no on/off button. It remains always turned on until the battery dies. Luckily, this unit is designed to run for over 10 years without the battery running out, and if it does, Gamma-Scout recommends sending the unit back to them for battery replacement and calibration but in my experience, it is fairly easy to replace the battery by your self if you know how to solder.

Unfortunately, this meter also has some downsides. There are some quality control problems including the radioactive logo being distorted and the upper and lower body parts not fitting perfectly even with screws tighten. These are small issues but they should not exist on a Geiger counter that cost almost 400 euros!

What bothers me the most is that the standard model does NOT come with a speaker! In my opinion, a clicking sound should be a standard feature on EVERY modern, handheld Geiger counter. Even my cheap 30 euro DIY Geiger counter has a tiny speaker built-in. If you want audible clicking sound then you need to buy a more expensive Alert model.

Overall, I think that Gamma-Scout is a-OK Geiger-counter but it feels outdated and I find it to be overpriced. That is why I would not recommend the Gamma-Scout standard model and I would suggest looking at other meters from the competition. A good alternative that comes to my mind would be Radiascan 701.

Hi, Today I want to tell you a little bit about an iconic soviet Geiger counter which is probably most famous for being used during the Chernobyl accident clean-up, the DP-5V.

It is primarily made out of a very strong, military-grade, green plastic. Some people love the colour while others hate it. I personally am somewhere in between.

The unit measures 19x17x8cm (with caring case) and weighs around 3kg. The cable connecting the Geiger counter with the probe is fixed and measures around 115cm which allows for moving the probe comfortable.

Unlike its older brothers, DP-5A and DP-5B, this Geiger counter doesn’t require the user to set the correct voltage manually before use. This means it is simpler and quicker to operate.

To power on the unit we simply need to turn the selector switch that is located on the right-hand side. Just like in polish DP-66M, the first position means the unit is turned off, the second is a battery test, the third is 200 R/h scale (bottom scale), the fourth is the upper scale in mR/h x1000, the fifth is the upper scale in mR/h x100 and so on until the eighth position which is x0.1.

The rotary switch is very hard to move which prevents the user from accidentally switching to a different scale. This being said, in my opinion, it is way too hard to move and I feel that I could break it just by switching from one scale to another. I much more prefer the selector switch on my Ludlum.

The scale on this unit, as well as the area around the selector switch, is covered in luminance paint (it is not radioactive like in DP-63-A). Unfortunately, since these units are pretty old, the glow does not last for very long. There are also two small light bulbs that can light up the display if we would be taking measurements in a dark environment. Turning the light on is done simply by flipping the switch on the left side of the unit.

Since this is a military Geiger counter, it is waterproof, however, I would still suggest you keep it away from a wet environment because the seals are old and can leak water inside!

Calibration can be done very easily by adjusting potentiometers after opening the unit.

One very annoying thing about this meter is the fact that it runs on obsolete soviet batteries. Luckily, it is fairly easy to make adapters for AA batteries using cardboard and some aluminium foil or to bend the contacts. The unit runs on 2 batteries while the third one is used to power on the light bulbs.

Another negative thing about this meter is its very small display which measures only 5x3cm compared to DP-66M’s 7.5x4cm or to Ludlum’s 6×3.8cm. The display on DP-5V also seems to be placed pretty deeply which makes the viewing angle much more narrow.

There is a headphone out but it uses a weird, obsolete connector which means that you can only connect the original headset to it. Sadly, mine did not come with the headset so I decided to make my own speaker using 2x screws, a buzzer with a generator and Polymorph plastic.

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On the bright side, the needle moves smoothly and doesn’t jump around like in Universal Radiation Meter Model 1700.

The DP-5V has two Geiger Muller tubes, an STS-5 for the lower range and a SI3bg for higher. The beta window has an area of around 3cm^2 which allows more particles to hit the tube making the unit more sensitive.

Originally, these units came with B-8 Strontium 90 check source, however, mine had its removed.

Wrapping things up, this unit is a solid Geiger counter and is a great choice if you are just starting out or you are looking for something with more Cold War vibe.

Hey guys! I hope you are doing well. Today I want to tell you a little bit about this lovely antique gamma scintillator so grab your morning coffee or evening popcorn (depends on what time zone you’re in) and enjoy.

This unit was produced (most probably) during the 1960s in Canada by a British company called Nuclear Enterprises. The meter itself is called Universal Radiation Meter Model 1700 and the serial number on my unit is 71.

What makes this unit unique is the fact that it was purchased and used by the Polish Nuclear Agency (Państwowa Agencja Atomistyki). How do I know that? Well, Poland was a communistic country until the late 80s. This meant that it was pretty much impossible to get things from outside of Poland (not to mention scientific equipment). The only people who had the power to import things were state agencies and party members. While being used by state agencies, this unit was modified to run of 4x AA batteries or a power supply (PT-1).

After the fall of communism, this unit was sold to the private market and then it finally found its way into my hands.

This meter although designed for scientific use is not very precise. The needle on the meter doesn’t stay in place and jumps all the time making it impossible to measure things accurately. What is more, the unit was most probably designed for high-level gamma radiation detection since weak samples are not (or barely) detected.

https://youtu.be/Nt8MVYpNI0c

Although not perfect, this meter is a really cool antique gamma scintillator with an amazing history behind it.

Greetings fellow radiation nerds!

Recently I managed to acquire an old, vintage, Polish Geiger counter from the early 70s, the DP 66M. What makes them a very interesting is the fact that they can measure anything from background to extremely high levels of radiation and they are really affordable costing as low as 50 euros/bucks on the used market!

My first impressions.

I got my unit from a warehouse, this meant it was stored in really bad condition. When it arrived, I had to clean it few times in order to get the dust off and remove unbearable smell of mould. If that wasn’t enough, batteries that were inside of this unit have leaked into battery compartment resulting in me not being able to remove the batteries! Luckily these units are fairly simple to disassemble and I managed to remove old battery compartment with a help of a hammer and replace it with a new one that I have build myself from a PVC pipe. Finally I managed to fire this guy up and luckily the unit was working fine, however calibration was way off, so I had to calibrate it. This Geiger counter uses military version of the same tube that is inside my Terra-P Geiger. This meant that I had a relatively good reference point for calibration. I used samples of pitchblende and uranium glaze from my collection in order to calibrate the unit (please note, this is not “professional” way to calibrate Geiger counter, but for the home use, I think it is more than enough). After cleaning, repairing and modifying my DP 66M, it was finally in a working condition and I could start measuring stuff with it.

How does DP 66M perform?

Despite being old unit from the 1970s, DP 66M still holds it ground and pushes modern digital Geiger counters to the test. There are 8 positions on the rotary switch. I did find it confusing at first so I made a table for you guys on how to read the measurements correctly.

W= Device is off

K = Battery check (needle should be reaching red K on the meter, if it is not, you need to change batteries)

200 R/h = use scale on the meter that goes up to 200. This is your reading in R/h

5 R/h = Multiply your reading from the 0-5 scale on the meter by 1. This is your reading in R/h

0,5 R/h = Divide your reading from the 0-5 scale on the meter by 10. This is your reading in R/h

50 mR/h = Multiply your reading from the 0-5 scale on the meter by 10. This is your reading in mR/h

5 mR/h = Multiply your reading from the 0-5 scale on the meter by 1. This is your reading in mR/h

0,5 mR/h = Divide your reading from the 0-5 scale on the meter by 10. This is your reading in mR/h

Now if you are little bit up to date you probably know that mili Roentgens are no longer used and have been replaced by Sieverts. Luckily it is relatively easy to convert mR to uSv, 10uSv is around 1mR. Here a table with the readings but in Sieverts

200 R/h = use scale on the meter that goes up to 200 and multiply you reading by 10. This is your reading in mS/h

5 R/h = Multiply your reading from the 0-5 scale on the meter by 10. This is your reading in mS/h

0,5 R/h = Multiply your reading from the 0-5 scale on the meter by 1. This is your reading in mS/h
uSv/h

50 mR/h = Multiply your reading from the 0-5 scale on the meter by 100. This is your reading in uSV/h5 = Multiply your reading from the 0-5 scale on the meter by 10. This is your reading in uSv/h

0,5 mR/h = Multiply your reading from the 0-5 scale on the meter by 1. This is your reading in uSv/h

The range on the unit is very impressive, from 0mR/h to 200R/h (0 – 2 Sv/h). This means you will most probably never run into 3,6 Roentgen situation. There are two other switches on the unit. The one on the left side with “KAS” written above it is used to reset measurement/zero the meter. This is helpful when you are measuring different samples and you don’t want to wait for the needle on the meter to drop down. Second one with OŚW. written above it, turns on a small lamp that allows you to see the measurement during the night or when there is little to no light. 
The meter on the DP 66M is made out of glow in the dark material which makes reading the measurement in the dark easy. Unfortunately, due to the age of the geiger the glow does not last long so I would not rely on it.
Bonus feature of the DP 66M is its ability of charging (zeroing) DKP-50 personal dosimeter. To do that simple unscrew cap and insert DKP-50 dosimeter, then use potentiometer to “zero” reading on the dosimeter.

Different DP 66 models.

Let’s start with the most basic version, the DP 66. The main differences between DP 66 and DP 66M are different external probe designs (they are still identical on the inside) and better quality components on the M (military) model. Also the DP66 measures in mili roentgens, roentgens and in CPM (0 – 1 000 000 CPM) while DP66M measures in mili roentgens and roentgens. Third variation is the DP66M1. It is identical to the DP66M except that the DP66M1 can be powered by an included power cable without needing adapter like the other models.

What to look for when buying DP 66M?

If you are considering buying DP 66M (or any other model from DP66 family), make sure you got some basic DIY skills and you are capable of doing some minor repairs. It would also be good idea to get in contact with a seller before buying and making sure that there was no battery leakage (like in my case) or any other problems with the unit in the past. Most units had their Strontium-90 check sources removed when they were decommissioned from military use, however some units can still have them. If you find one that has it, lucky you! In terms of price you can find them in “unknown condition” for as low as 30 euro/dollars on European used market. If the unit is in good working condition the prices might be higher, ranging from 40 to 70 euros/dollars (in states, prices can be higher). Anything above that I would consider a rip off unless it’s made out of gold.

Conclusion.

If you are in the market for a Geiger counter that won’t break the bank and has Cold War vibe, I would highly recommend the getting DP 66M as long as you got some basic DIY skills just in case if the unit needs few mods or repairs. I hope you enjoyed this review of the DP 66M Geiger counter. If yes please feel free to subscribe to my blog and let me know in the comment section what is your your experience with Cold War Geiger counters!

Cheers!