Радиометр РК-01
Hello, friends! Recently I managed to acquire another rare device for my collection: this is a pocket radiometer RK-01. I've been hunting for one like this for a long time, and finally luck has come, I have the device. However, you can see for yourself, that the radiometer's condition is a C minus. The body is very battered. On the bottom side the paint is almost completely worn off along with the primer. The screen is torn.
The condition on the top side is better, but on the body we see many scratches, dents, and some writings. The carbolite plugs of the range regulators are missing, screws are screwed in instead. However, one plug still remained, but it is also broken. The leather strap turned into hard plastic, and besides, it is broken in half and held together with a screw. The power control button is not original. Some of the screws that secure the body are missing.
The switch handle is also missing, instead of it is installed conditionally suitable in size, but inappropriate in the way of attachment, it is not fixed. In general, even from the appearance it is clear, that the device was used not just actively, but mercilessly. But, nevertheless, let's see what's inside the radiometer.
And inside it is heavily dug up. Two counters are not original, there must be SI-1BG and SI-2BG, and instead of them there are SI-10BG and SI-11BG. They are a little off in size, but the characteristics, fortunately, are similar. Unfortunately, because this counter is longer, there was no room in the radiometer for a second internal pillar, with the help of which the halves of the body are fastened together.
Well, and accordingly, there is no clamping plate for the counter either, and the counter is soldered to the neighboring one. At least one original electrolytic capacitor remains, and most of the capacitors have already been replaced with newer ones. In general, these capacitors don't last that long.
and most likely, this electrolyte also needs to be replaced. Two transistors are also not original, they should be P14, but they are MP40. Well, the diode is also not original.
The button here is electric with wires, although structurally it should be mechanical. And here there should be a tab that closes the contacts when pressed. There are still many traces of soldering, which once again confirms the difficult life of a radiometer. They repaired it many times and clearly didn’t want to let it retire. But looking ahead, I will say that the device, despite the problems, it is still conditionally working.
Of course, I will not claim that it functions exactly as intended, however, I have already checked it, there is an adequate response to the radiation source on all subranges. So I want to restore it to the best of my ability, and then we will consider the purpose of the RK-01 radiometer and its structure. And I will say in advance that the design of the device has many unusual and interesting points. The original handle of the RK-01 radiometer is metal and does not look at all like the one with which it came to me. Unfortunately, the search for the original part yielded nothing. But this handle doesn't fit here, since it is not fixed on the switch shaft, and it is simply not usable.
So I printed a new handle on a printer, melted a threaded bushing into it, and it turned out to be a completely functional part. I'll leave this option for now, but maybe someday I will be able to find an original handle or make something more suitable. Having made the handle, I noticed, that after a long period of inactivity the radiometer has difficulty reaching the operating power mode. As a rule, it is always connected with the exhaustion of gas-discharge stabilizer SG-301S – it takes a very long time to ignite. And so when checking the power supply, the needle goes off the scale, which indicates that the voltage is not stabilized. The point is that the glow discharge stabilizer, according to the passport data, is designed for 1000 hours of operation.
Therefore, in devices that were actively used, these components have already exhausted their service life. And the first thing I'll do is replace this part. The procedure is very simple, the stabilizer is accessible without the need for disassembly, therefore we unsolder its leads and push it out.
We insert the new part in place of the old one and solder the leads. In addition to replacing the voltage stabilizer, I replaced the remaining electrolytic capacitors with new ones. The old ones are completely unusable, they dried up long ago and lost their capacity. So, although it was a pity to part with them, but this operation is necessary.
By the way, it turned out that they are no longer original either, one from '71, the other from '67. But these capacitors turned out to be completely serviceable, that's why I didn't replace them. As a result, after replacing parts the radiometer finally started working properly. Now when checking the power supply the needle moves smoothly and without going off-scale beyond the red mark and slowly returns to its original position, and the device is ready for use immediately after switching on. And before it was necessary to turn it on and off many times, to wait, to hope – in general, the radiometer did not work rather than worked. Now let's pay attention to the screws that act as plugs.
The original plugs are made of carbolite, but three of them are completely lost, and one remained, but its head is broken. There is no place for screws here at all, so I printed 4 new threaded plugs on the printer, and they look almost like standard ones. The original strap cannot be restored, so i will make a new one from faux leather. The leather used here is hard, and there is an assumption that the strap is used, among other things, as a stand when the device is lying on the table. But I couldn't find one that was as rough, so we'll have to use what we have. Besides the artificial one, I also have a strip of genuine leather, that's why I decided to make this option too.
Although real leather is even softer than leatherette. But I'll see what I like best. Now I want to restore the body.
First of all, I will need to remove the old paint from the bottom of the body and straighten out the dents. Then I will prepare the surface and I will cover it first with acid primer, and then with filling. I'll have to use putty somewhere. After these operations, the body can be painted. The top part will be almost the same, but there is a marking here, so I'll tape it up so I don't paint over it, and then I'll have to finish painting it by hand. Of course, the radiometer will not look like new, but I think that its appearance will improve significantly.
The beta filter flap is chrome plated brass plate. It looks very shabby and the coating needs to be restored somehow. Unfortunately, I don’t know how to chrome parts, but I want to try to plate it with nickel. I don’t know whether it will work or not, I’ll try.
The idea of covering the markings with tape turned out to be a failure and had to be redone. The method turned out to be much more successful with full painting of the top panel, and the grooves of the symbols can be scratched again. It was difficult, but I am very pleased with the result. I also really dislike the fact that the radiometer is missing one inner pillar, because of which the upper part of the body is held by a single screw.
The reason for this is that originally the instrument used a SI-2BG meter, which is shorter. And now the SI-11BG is installed, which is one and a half centimeters longer, and it overlaps the location of the pillar. That's why it was removed at some point. I thought for a long time about what to do with this, I even wanted to put a SI-3BG counter, but it is several times less sensitive, that's why I didn't like this idea.
But when I unsoldered the meter, it turned out, that it can be slightly bent to the side – there is some space here, although it is a bit tight. Then the pillar will fit into its original place without any problems. I'll need to solder a stiffer wire to hold the meter well. Or I'll connect it to the standard terminal. And I will insulate the pillar itself.
The original part is aluminum, but I'll put a brass one because that's the only one I have. So, first I soldered the counter to a thick wire, but then I came up with a better idea. I installed this holder on the board and thus killed two birds with one stone: firstly, space was freed up for a pillar, and secondly, no soldering is needed here anymore, the counter is now easy to insert and remove. Then I screwed the pillar into place, and now the body can be fully fastened using all 4 screws. I also successfully nickel plated the beta filter plate, it is no longer shabby. The nickel certainly doesn't shine like chrome, but it's still much better than it was.
Well then, friends, after the restoration, my radiometer was significantly transformed, and plus, I made a user manual for it based on the original brochure. We'll look at it later, now let's get acquainted with the purpose of the device. RK-01 is designed to monitor radiation safety on gamma and hard beta radiation in laboratories, in production as well as in the field. It was developed at the Institute of Biophysics in Moscow, the first RK devices appeared in 1958 and were produced at least until 1960. I even managed to find out the name of the developer – this is candidate of technical sciences Viktor Vasilyevich Markelov. And production was located at Moscow Plant No. 642,
which still exists and is called the Vympel Machine-Building Plant. In August 1946, under the leadership of Igor Kurchatov a radiation laboratory was organized in order to create safe working conditions in the nuclear industry. The laboratory was later transformed into the Institute of Biophysics. The Institute's task was to ensure radiation safety of personnel involved in nuclear production at all its stages. This included the development of dosimetric monitoring devices, radiation safety standards, organization of the work and rest regime of personnel in the conditions of nuclear production.
The institute also created special protective equipment from many types of radiation and developed prevention methods and treatment of radiation injuries. And I think that this device, which is in my hands, has seen so much radiation that it is difficult for an ordinary person to imagine. And what tasks and in what quantity were accomplished with its help, we can only guess. Just in case, I’ll calm the radiophobes – there is no radiation contamination on the radiometer, I have thoroughly washed it, checked it and it does not emit any radiation. In the late 50s the bulk of the radiometers were quite large, although the technology already made it possible to create compact devices, which would be convenient to carry with you.
It should also be noted here, that in those years all laboratory dosimetric equipment were devices based on ionization chambers. An example of such a device is the MAK microroentgenometer. But the RK-01 was the first portable device, where halogen meters were used. It is difficult to say how much demand there was for such radiometers, however, the RK-01 was produced for three years, and after it the RK-02 device appeared, created at the same Institute of Biophysics, moreover, it was produced until the end of the 80s.
By the way, there is a very good review of the RK-02 on the Vickydseek channel, I'll leave the link in the description under the video. Pocket radiometer RK-01 is a small-sized device weighing only 650 g and measuring 170×80×50 mm. It has 4 working ranges for measuring gamma radiation from 0 to 1 μR/sec, up to 10, 100 and 1000 μR/sec. And the radiometer is also suitable for measuring beta contamination of surfaces from 0 to 100 particles per cm²/sec and beta particle fluxes up to 35 particles per cm²/sec.
The device has a very small error on all ranges – no more than 10%. It is powered by a single 1.5 volt cell of size 373, and the operating time is up to 200 hours.
RK-01 operates at temperatures from –40 to +50 degrees and at humidity up to 98%, although it must be said that it does not have any airtightness, and is also not protected from dust. Inside the radiometer there are three counters of different sensitivity – these are STS-5, SI-1BG and SI-2BG, thanks to which the device is able to work in such a wide range of measurements. There is a measuring device on the front panel – this is a microammeter M592, power check button, range regulator plugs and a switch for operating ranges. The instrument scale is graduated in μR/sec, which is quite unusual – but we remember, that RK-01 was designed for laboratory use. At the bottom we see an engraving with the name of the radiometer model, year of manufacture and number.
On the left side there is a battery compartment, which is closed with a screw-on aluminum lid. One cell of type 373 is installed here, which is placed positive-side out. On the sides of the case there are fastenings for a strap which is made of artificial leather.
The strap is needed mainly for safety, when the device is in the hand, and it can also be used to carry the radiometer. By the way, the RK-01 was supplied in a special leather case. There is a beta window on the back cover of the device, which is closed with a brass screen.
The window is located opposite the highly sensitive STS-5 counter, which is capable of working with hard beta. To turn on the device, you need to turn the switch and select any required measurement range. When we turn it on, we immediately hear the familiar whistle of a blocking generator. Using the “K” button the voltage of the power supply cell is monitored.
The needle should move beyond the red mark on the scale. The mark corresponds to a voltage of 1.1 V, and if the needle does not reach this line, then the battery needs to be replaced. Let me remind you that the scale is graduated in μR/sec, and if you convert them into μR/h, then on the first range the very first mark means 0.04 μR/sec, or 144 μR/h.
And the full scale is 3600 μR/h. On the last range the limit is 3.6 R/h! That is, RK-01 is completely unsuitable for measuring near-background values. And this is not surprising, the radiometer was intended for serious laboratory research.
However, it still reacts to weak radiation. This is my cesium source, it emits somewhere around 60–80 μR/h. And that's about what we see on the scale.
The manual does not mention, how should beta radiation from an object be measured, but it is obvious that such a measurement can be made only with the STS-5 meter, that is, on the first range with the curtain open. The entire scale is taken as 100 particles per cm²/sec. Let's open the curtain and we'll bring some beta source, and now we see the device gives some readings. Considering that uranium glass emits virtually no gamma radiation, the beta flux density can be estimated at 10 particles per cm²/sec, or 600 particles per minute. Let's compare with another radiometer – As you can see, the result is very close.
Let's now take a gamma source, and here we will need the range “×10”. The device shows a dose rate of approximately 2 μR/sec. And to test the 3rd and 4th ranges, I need an even stronger gamma source, which I don't have, so we will check them after disassembling the device, but with a beta source. Let's take a look at the schematic diagram and the internal structure of the RK-01 radiometer.
There are some very interesting features here. The device's circuit diagram is quite simple. On the left side there is a blocking generator, which converts the voltage from the battery into high voltage. Here we come to the first interesting point, which has never been encountered in other radiometers: after the transformer we see a voltage doubler, assembled on two selenium rectifiers and two capacitors. That is, the transformer does not immediately produce 400 volts, necessary to power the meters, and produces a conventional 200 volts, which are multiplied by two times, and only then the resulting voltage will be stabilized using a gas-discharge stabilizer SG-301S. Let's find all these parts on the board.
This is a transformer, blocking generator transistor, here is a rectifier diode, here are two selenium rectifiers ABC-1000, one of the capacitors, and the second one is in the depths. Well, this is the voltage stabilizer we are familiar with. Further on in the diagram we see 3 Geiger counters with different sensitivity. When the pulse passes through the counter the corresponding capacitor is recharged. A high-resistance resistor is connected in parallel to the capacitor, through which the capacitor discharges. What's interesting here is that that in all other radiometers that we know, range calibration is carried out using trimmer resistors, and RK-01 has it implemented through trimmer capacitors.
The last counter has two such capacitors, for 3rd and 4th ranges. When the range “×100” is turned on capacitors operate in parallel, and their capacity is summed up. And there is only one resistor here. And this is how these parts look in real life.
The next interesting feature is the mode switch. We are used to rotary switches, but in RK-01 it is not like that at all. The diagram shows metal plates with a bold line which close certain contacts when turning the switch.
This is what the mechanism looks like: you see two semicircular brass plates, and on the sides there are spring-loaded contacts, which close when switching. This part turns on the power supply to the device, and this one connects the meters. If you look at the diagram more closely, then we will see that when the first range is turned on all 3 counters will be activated in parallel mode, on the second one SI-1BG and SI-2BG will be working, well, on the rest – only SI-2BG. This is done for the purpose of to avoid the needle from going back in case of overexposure, when the STS-5 and SI-1BG counters switch from pulse mode to current mode.
Well, then the current goes to the amplification circuit, running on two transistors, and then goes to the microammeter. These are the transistors on the board. It is interesting that for the sake of compactness the microammeter has the usual contact pins removed, and the wires come out from the side. And finally, the Geiger counters, there are three of them here. The most sensitive is STS-5, it operates on the first range with both gamma and beta radiation.
The second counter is SI-1BG, or its analogue SI-10BG, as I have. This is a medium sensitivity meter for radiation powers up to 1.5 R/h. And the roughest one is the SI-2BG counter, or, as here, the similar SI-11BG, capable of registering radiation up to 50 R/h.
And let's check the operation of RK-01 on the last two ranges. Let me remind you once again that only the SI-2BG counter is used, instead of which the SI-11BG counter works in my radiometer. On the range “×100” the check source is expected to cause an off-scale reading.
On the range “×1000” we see the readings, approximately corresponding to 3 R/h, which is very close to the truth, because other devices somehow estimate this source in the same way. Well, the diagram turned out to be extremely unusual, this is the first time I've encountered something like this. So for me it was very interesting. Now I suggest you get acquainted with the operating manual for the RK-01 device. It is a small book, and in the original it is a little smaller than what I made. But for the rest I retyped and redrawn everything very accurately.
At the very beginning we see a description of the purpose of the radiometer and its technical characteristics. What follows is very interesting and useful description of the operation of the electronic circuit of the device. This is followed by a chapter devoted to working with a radiometer. As always, there is a short list of faults, and also the circuit diagram of RK-01. And at the end there is a graph of non-linearity of readings on the last range. Well, here is the device passport.
We got acquainted with another unique example of Soviet atomic science. I am very pleased that I finally managed to acquire the RK-01, even in such a worn-out condition. In this case, I don't consider its problems to be shortcomings. The radiometer worked very hard, obviously brought a lot of benefit, and with its direct help developed the cause it served.
And I must say, that most of the RK-01s that have survived to this day also quite battered by life. Somewhere they were repaired, somewhere they were modified to suit their tasks. Only one RK-01 was found in its original form – it was lucky and got into the museum. I also put my hand to my device – I fixed its power supply circuit, fixed the meters, made the missing parts and restored the body. It will be very interesting, if you share your emotions about RK-01 in the comments. Write what seemed unusual and surprising to you.
And with that I say goodbye, thanks to everyone who watched! Until next time!
2025-04-30 23:55
