Voltcraft Dosimeter - Radiometer | RKSB-104 contamination meter [teardown pics] - Page 1
Forum section: electronics / testgear

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: September 09, 2017, 05:51:45 pm
content: Dear forum,some of you might have noticed that I am a sucker for older hand held electronic devices.Today I can give you some teardown pictures and basic info on my newest acquisition: A contamination meter that can detect gamma and beta particles.This meter is a re-branded, Russian made RKSB-104 with two radiation-counter tubes.Features (non-exhaustive):radiation dose equivalent measurement (0.1 ... 99.99 µSv/h)two measurement time frames, short - low precision, long - higher precisiondetection of gamma and beta particlesenergy field of measured radiation: 0.5 ... 3 MeV (beta) and 0.06 ... 1.25 MeV (gamma)DIP switch configurable detection modesmeasuring mode and surveillance mode with selectable warning threshold9V battery poweredportableThis is a pretty straight forward and simple device. It is not a precision instrument but can be very useful in prospecting radioactive minerals or checking for surface contamination. Sadly it does not have a counts-per-minute mode.It can detect ionizing radiation but will only give quantitative data. To get qualitative data e.g. what kind of radiation one is looking at, higher quality equipment such as a scintillation detector is needed. Scintillation spectrometers can also detect alpha particles and are able to tell specific radiation characteristics apart, thus providing means to look for radiation sources in foods or accurately identify various sorts of radio isotopes. (The concept of scintillation detectors is very interesting in my opinion and very well worth taking a closer look at!)The Voltcraft Dosimeter – Radiometer came with its original protective case. (just minor surface defects on the front lid, looks like from a hot soldering iron)It was working out of the box after inserting a 9V battery, the LCD has started breaking down however.This is the back with the beta-particle filter attached.Beta-particle filter and battery compartment lid removed.Three screw have to be removed to open the device. The bottom screw was "sealed" with some black wax-like gunk.Inside there are two SBM-20U tubes. Checkthis site for technical reference.Here is the front PCB with LCD and large piezoelectric speaker. The LCD shows some break down but apart from the blots along the edges it still works fine.The assembly consists of two double layer PCBs, connected on the lower edge via blank wires. In between the two PCBs there is a piece of fiberglass filled epoxy resin board as an insulator, held in place nicely with three plastic mounts.PCB A frontPCB A backPCB B frontPCB B backInside of the housing (there was some soft foam in the battery compartment that I already removed - it was completely disintegrated).Some variants of the RKSB-104 feature a connector for external probes, such as higher sensitivity pancake probes etc. The board of the Voltcraft has the corresponding traces, but no connector is populated.Also, the backside of the housing looks like it is prepared to hold a probe connector (minus the through-hole).If you are interested in looking into the provided manual (German), please let me know. I will eventually put it on my flatbed scanner and build a PDF file. It is a very funny size (74mm x 120mm brochure) and looks like it was duplicated on a hectograph. I am not sure about that however, since I can only remember purple colored ink for this process. On second thought it maybe was printed on a mimeograph machine - who knows.The meter does not seem to have been used much and right out of the box it gives some sane values for the backround radiation that is to be expected in this area of Germany.Operation is pretty convenient. Once you have set the detection mode via the DIP switches in the back (in this case gamma detection, dose equivalent reading), you select the acquisition mode (27-28 seconds or 270-280 seconds) via the X 0.01 / X 0.001 switch, set the MESS/MELD switch to MESS (measure/warn) and turn the device on (EIN/AUS). The device starts counting and after the set time has elapsed, the speaker beeps several times and you can take the reading from the display. In my case it reads 0175 in the more precise acquisition mode. The value has to be multiplied by 0.001 to get the scaled value in µSv/h = 0.175 µSv/h.To do surface contamination screening for beta particles you need to configure the DIP switches differently and remove the back shielding. There is also another measurement mode, namely measurement of specific activity from Cesium-137.You can configure 31 different warning thresholds from 0.1µSv/h up to 16µSv/h.In surveillance mode the device draws around 0.8mA. I am using Ansmann 9V batteries (for smoke detectors)9V battery comparison tests840mAh (from the test results in the link above) should give about 1000 hours or 42 days - that is not too bad for my tasteThe surveillance mode works just like the measurement mode with some differences: The internal speaker gives an audible "tick" for every particle detected (measurement mode is silent) and the measured dose equivalent reading is zeroed every complete cycle without beeping feedback. This way, the device can be used as a sweeping scanner for surfaces and provides quantitative audible feedback alongside the displayed reading.I hope this was at least a bit interesting for you all. I could not find anything on the RKSB-104, Radian-104 and similar re-branded devices here on the forums and thought some of you might be interested.Best regards,Frederik

author: Emo
author_rank: Regular Contributor
timestamp: September 10, 2017, 07:26:38 pm
content: Hi Frozenfrogz,A simple schematic is available for this instrument, see attachmentEric

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 10, 2017, 08:15:03 pm
content: What is the reason it has 2 tubes in parallel? I can't remember seeing this before...

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: September 10, 2017, 08:38:48 pm
content: Thanks Emo,maybe I can do some reverse engineering and clean up in KiCAD next time there is real bad weather and not much else to doQuote from: PA0PBZ on September 10, 2017, 08:15:03 pmThere are several detectors out there with 2, 4 or even more tubes in an array. My guess is, that it gives more accurate readings especially when doing surface screening. The DRG-06T has 4 built in SBM-20 tubes if I remember correctly.

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: September 11, 2017, 05:24:18 pm
content: ErratumThere is no true audible feedback on counting a particle - neither in measuring mode nor in surveillance mode. The tubes "tick" every time a particle hits. This tick is very quiet and since I tried the surveillance mode late at night and my ears had adopted to the overall low sound levels I misinterpreted the ticks as coming from the internal speaker. However, I have seen some hints onmodding the devicein case one wants the typical Geiger-counter ticking.Also, the count/signal path seems to be broken out to the unpopulated soldering through holes for an eight pin DIN socket, so hooking the device up to an Arduino should be easy

author: kt3102em
author_rank: Newbie
timestamp: October 11, 2024, 07:32:51 am
content: I see the topic is not active, but for the sake of history I will add that there is such a version of the circuit in good quality. And it is possible to output a sound indication of particle registration using one low-power diode. See photo.