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 2.GQ Geiger Muller Counter
 Modifying GMC500+ to support extern Counter Tubes
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Geo-Johnny

Austria
154 Posts

Posted - 10/07/2019 :  13:14:53  Show Profile  Reply with Quote
The new version of the GMC500+ is ideal for DIY and experiments thanks to the dual technology of the two counter tubes, the automatic and manual voltage adjustment, the separate calibration option and the separate dead time setting. Inspired by the colleague Stargazer_40 and his wand solution, I have realized a high voltage output for the connection of different counter tubes by means of a 3,5mm hollow plug socket(like the DC jack of old Nokia phones). When connecting an external counter tube, one of the two inner counter tubes is automatically switched off. Ideally, the internal counter tube 1(M4011) should be switched off and its AVA used for the output. After much deliberation, I decided to switch off the internal counter tube 2(SI-3BG) because of the shorter internal cable routing. It is more important to me to set the high voltage manually for the external counter tube itself.

A few components:


High Voltage Output:




Finished:


Everything works great. It has already been tested with several counter tubes, only the new LND712 tube shown above is broken. The seller sends me a free replacement. The outer conductor of the coaxial cable is the anode lead and shields the inner counting cathode lead. This saves you a separate shielding.

Sequel follows ...

Edit: The internal anode resistor was not used externally. It is the full high voltage at the output. So each external counter tube needs its own special anode resistor near the anode itself! This is the better solution because each counter tube type needs a different value for the anode resistance.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20

Edited by - Geo-Johnny on 10/07/2019 13:28:19
Reply #1

Geo-Johnny

Austria
154 Posts

Posted - 10/07/2019 :  14:04:43  Show Profile  Reply with Quote
A store and restore function of the user settings in the GMC Data Viewer / Logger Pro would be very desirable for my purposes. So I could save the settings for all external counter tubes in different profiles and restore if necessary with a mouse click for the currently used counter tube. Please support, so build a store and restore function in the programs! It would also help many other users.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #2

Stargazer 40

USA
346 Posts

Posted - 10/07/2019 :  18:27:07  Show Profile  Reply with Quote
Very nice. I used a three pin din plug for the connection. The 3.5mm mini plug is much more available. There still is a problem with voltage drop out of plateau region for high counts, but really I think this mod (like my V1 500+) will allow testing many different tubes with a manual measure of voltage. Not convenient, but once you map percentage to voltage it's done.

Like the appliques on the HV warning. :=)

It will make the stock 500+ more expensive, but really we need to get AVA applied to both tubes for constant voltage no matter the CPM.

Stargazer 40

Edited by - Stargazer 40 on 10/07/2019 18:29:02
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Reply #3

Geo-Johnny

Austria
154 Posts

Posted - 10/07/2019 :  22:50:49  Show Profile  Reply with Quote
@ Stargazer_40, you are 100% right, a further development of the GMC500+ in relation to the AVA for both counter tubes would be highly recommended and desirable. The manual setting of the high voltage is not a problem for occasional tests, automatically is easier of course. Much more important to me personally would be a store / restore function for the user settings. No matter how the development progresses, it's certainly not my last Geiger counter from GQ Electronics.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #4

Stargazer 40

USA
346 Posts

Posted - 10/08/2019 :  03:56:52  Show Profile  Reply with Quote
The latter they have agreed to pursue. There is always lead time for hardware change, but GQ is very nimble and we can hope.

Stargazer 40
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Reply #5

Geo-Johnny

Austria
154 Posts

Posted - 10/17/2019 :  07:55:11  Show Profile  Reply with Quote
Today my replacement LND712 counter tube arrived. Immediately I connected it to the GMC500+ and tested it. Everything works perfectly. Nice would be a separate calibration menu for calibration, dead time and voltage setting for an external counter tube. Ok, you can not have everything, so I'm going to make the GMC600+ myself a Christmas present.

Edit: And here is my Calibrationsdaten for the LND712 counter tube externally on the GMC500+ as counter tube 2 ...

Tube Voltage: ~500V = 60%
Calibration: 525CPM = 4,85uSv/h
Dead Time: 90uS

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20

Edited by - Geo-Johnny on 10/17/2019 08:36:35
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Reply #6

Stargazer 40

USA
346 Posts

Posted - 10/17/2019 :  14:29:33  Show Profile  Reply with Quote
Thanks Geo-Johnny for the calibration data. I'll compare with my LND712 and see how I faired on these two points.

Stargazer 40
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Reply #7

Damien68

France
58 Posts

Posted - 10/17/2019 :  23:31:54  Show Profile  Reply with Quote
often these cables that you use are not coaxial cables but consists of 2 independent wires surrounded by a sheath.
In all cases it must work but it must still remain sensitive to electromagnetic disturbances.

Especially at the level of the tube, if for example you approach your hand to the cathode tube this must create disturbances.

That is why the recommended connection of the LND-712 and all alpha window tubes in general is not the same as for a classic tube.

See datasheet:
https://www.sparkfun.com/datasheets/Components/General/LND-712-Geiger-Tube.pdf

The detection is not done on the cathode current sensing but on the anode current sensing through a splited anode resistor, and the cathode is directly connected to the ground.

We could try to make the same connection using 3 outputs (Ground, HV, Signal) and a splited anode resistor + a high voltage decoupling capacitor.
GND is PCB Ground
HV is M4011 or tube 2 Anode connection (before anode resistor)
Signal is M4011 or tube 2 Cathode connection

The pulse will be reversed but it should not disturb, But I do not think it will work because in this configuration the detection is sensitive to the HV generator noise.
If the HV power supply is too noisy (not regulated enough) it will create detections. in my opinion it will be the case.

When I have time, I will try to do it to see what it gives.

The best I think is to do as you did but to keep a cable short enough

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 10/18/2019 00:07:21
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Reply #8

Geo-Johnny

Austria
154 Posts

Posted - 10/18/2019 :  00:52:29  Show Profile  Reply with Quote
@ Stargazer_40, my calibration values are not exact. These are values that can easily be set on the device itself in mobile use, because the CPM value can only be set in hundreds of steps. For a very precise setting, you must calibrate the values via the data logger via the PC. But with about 3 to 5cm distance of the source to the counter tube, these are my values sufficiently accurate. Therefore, I wish for mobile use a small app for the smartphone, with which you can set or synchronize the calibration, the dead time, the counter tube high voltage and the time.

@ Damien68, I used the shield for the anode side and the inner conductor for the counting cathode. Even with about 80cm cable, I have no electromagnetic interference, which affect the count (the smartphone is at a distance of 10cm next to the cable). I soldered the 10MOhm anode resistor directly to the plug of the counter tube. It works ...

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20

Edited by - Geo-Johnny on 10/18/2019 01:06:22
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Reply #9

Damien68

France
58 Posts

Posted - 10/18/2019 :  01:41:22  Show Profile  Reply with Quote
@Geo-Johnny
is OK and reliable,
Smartphone is not a problem because his frequency is high and cutted by filter.
Many switching mode power supply or other can be.
But there is just to be careful though.
We can make some test with the foolowing unit for 23€:
https://www.amazon.fr/Sourcing4U-Executioner-Mosquito-Swatter-Zapper/dp/B003TT3GDC/ref=sr_1_1

Image Insert:

112666 bytes
image is from Amazon site.


This make hard noise around GM tube pulses bandwith

for example if i aproche it near my GMC-500+ this disturb it strongly.

This is normal and not critical, and it certainly do for all similar counter of the market. But is in this case a good test to know about EMI immunity
and a good device to kick the bugs :)

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 10/18/2019 03:28:12
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Reply #10

Geo-Johnny

Austria
154 Posts

Posted - 10/18/2019 :  05:35:38  Show Profile  Reply with Quote
Of course, such devices disturb the Geiger counter, of course. But you could use the high voltage part of such a killing machine for a DIY Geiger counter, especially since these things are cheap to buy.

Back to the topic ... I am eagerly waiting for any small smartphone app for the GQ Geiger counters. Unfortunately, I can not program it myself, so I hope that this is a programmer read and finally published a mobile help for the GQ GMCs.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #11

Gelu

Romania
16 Posts

Posted - 10/18/2019 :  06:32:26  Show Profile  Reply with Quote
quote:
Originally posted by Damien68

often these cables that you use are not coaxial cables but consists of 2 independent wires surrounded by a sheath.
In all cases it must work but it must still remain sensitive to electromagnetic disturbances.

Especially at the level of the tube, if for example you approach your hand to the cathode tube this must create disturbances.

That is why the recommended connection of the LND-712 and all alpha window tubes in general is not the same as for a classic tube.

See datasheet:
https://www.sparkfun.com/datasheets/Components/General/LND-712-Geiger-Tube.pdf

The detection is not done on the cathode current sensing but on the anode current sensing through a splited anode resistor, and the cathode is directly connected to the ground.

We could try to make the same connection using 3 outputs (Ground, HV, Signal) and a splited anode resistor + a high voltage decoupling capacitor.
GND is PCB Ground
HV is M4011 or tube 2 Anode connection (before anode resistor)
Signal is M4011 or tube 2 Cathode connection

The pulse will be reversed but it should not disturb, But I do not think it will work because in this configuration the detection is sensitive to the HV generator noise.
If the HV power supply is too noisy (not regulated enough) it will create detections. in my opinion it will be the case.

When I have time, I will try to do it to see what it gives.

The best I think is to do as you did but to keep a cable short enough

Hi, with my apologies, I try to express my own opinion about what Damien68 expressed. For the measurement of Alpha, Beta, Gamma, these tubes are constructed specifically to be snsibile for the corresponding wavelengths. The signal is recommended, as a rule, to reap the Katod with a resistance of 100KOhm to GND. One primary reason is to have a maximum signal/noise gain. The second reason is to protect the circuits that process the useful signal from high HV values. It is true that it works with very small currents but it is about the high potential of tension. A third reason would lose the gain signal/noise.
I agree with Damien68, when he said that I need a coaxial cable with the third shield. I argue this, by the fact that the third shield binds to a single point of GND, preferably to the device, to cancel the loop against the GND.
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Reply #12

Gelu

Romania
16 Posts

Posted - 10/18/2019 :  06:52:02  Show Profile  Reply with Quote
quote:
Originally posted by Damien68

often these cables that you use are not coaxial cables but consists of 2 independent wires surrounded by a sheath.
In all cases it must work but it must still remain sensitive to electromagnetic disturbances.

Especially at the level of the tube, if for example you approach your hand to the cathode tube this must create disturbances.

That is why the recommended connection of the LND-712 and all alpha window tubes in general is not the same as for a classic tube.

See datasheet:
https://www.sparkfun.com/datasheets/Components/General/LND-712-Geiger-Tube.pdf

The detection is not done on the cathode current sensing but on the anode current sensing through a splited anode resistor, and the cathode is directly connected to the ground.

We could try to make the same connection using 3 outputs (Ground, HV, Signal) and a splited anode resistor + a high voltage decoupling capacitor.
GND is PCB Ground
HV is M4011 or tube 2 Anode connection (before anode resistor)
Signal is M4011 or tube 2 Cathode connection

The pulse will be reversed but it should not disturb, But I do not think it will work because in this configuration the detection is sensitive to the HV generator noise.
If the HV power supply is too noisy (not regulated enough) it will create detections. in my opinion it will be the case.

When I have time, I will try to do it to see what it gives.

The best I think is to do as you did but to keep a cable short enough

More wish to make a remark, never send through a high-value HV cable, even if it has shieling, or uncoupling capacitiva, to such types of devices. As an example, there are appliances that read high Gamma fields, they use complex detectors, which receive low DC voltage values, to feed the Power module of HV which is very close to the detector (Geiger Tube). And the signal picked off the Katod, is modulated in the current and sent back to the monitoring point. It prefers modulation in the current under different standards of signal issuance to suppress the noise.
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Reply #13

Damien68

France
58 Posts

Posted - 10/18/2019 :  13:21:41  Show Profile  Reply with Quote
@Geo-Johnny
I made my app under windows, I know that Android supports natively the USB/CDC class necessary to communicate with the counter there is no software particular difficulty. What GQ do?
after if we connect a counter to a smartphone, I'm not sure if it's really feasible.
There are normaly hardware protocols to follow in USB connection, the current available on the USB port of the smartphone in OTG mode is not necessarily compatible with the current management done in the counter unit, mostly if counter try to charge his own battery.
Today, all pc can provide 500mA on their USB port, for smartphone it's less sure.

In fact the feasibility is not necessarily obvious,there may be hardware issues.

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 10/18/2019 13:37:41
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Reply #14

Geo-Johnny

Austria
154 Posts

Posted - 10/18/2019 :  13:37:25  Show Profile  Reply with Quote
No idea. In any case, we first have to find someone who can program an app for Android and / or IOS. Then you can decide whether the app should connect to the GMC via USB, Wifi or both.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #15

Damien68

France
58 Posts

Posted - 10/18/2019 :  13:46:27  Show Profile  Reply with Quote
it's stupid I know someone who already mastered all this, he programs apps on tablet for wifi devices that I made, but I can not ask him that.

Mastery is acquired by studying, with it everything becomes simple
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Reply #16

Stargazer 40

USA
346 Posts

Posted - 10/18/2019 :  15:54:02  Show Profile  Reply with Quote
Gamma sensitivity of LND712 is 1080 CPM according to LND. That's for a Co60 source which is mostly higher energy gammas. I normally go with their published numbers.

Stargazer 40
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Reply #17

Geo-Johnny

Austria
154 Posts

Posted - 10/18/2019 :  23:02:17  Show Profile  Reply with Quote
I'm generally convinced that the WiFi module should be exploited much more in the newer GMC500 and GMC600. Just sending the data to the world map server is not enough. If you are already in the same network via a router or hotspot connection, you should use this immediately for a data and control exchange, as the function for the world map server is not affected. Therefore, it would be important for smartphones, tablets and computers to program software that can communicate with the GMC via Wifi. That would make the GQ GMCs much more valuable. The older models will not be enough room for the necessary code in the firmware, but with the newer GMCs should be possible without problems.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #18

Damien68

France
58 Posts

Posted - 10/19/2019 :  01:02:55  Show Profile  Reply with Quote
You're right Geo-Johnny, I did not think about that, to communicate via wifi between a smartphone and a counter, it's necessary that the firmware of the counter is made for that.
In fact, as it's, it can't work.
ESP-12s inside the counter is a ESP-8266, is a cheep version of the ESP-32 and dedicated to IOT device but without Bluetooth. It would have been ideal to can have bluetooth connection.

Mastery is acquired by studying, with it everything becomes simple
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Reply #19

Geo-Johnny

Austria
154 Posts

Posted - 10/20/2019 :  08:54:37  Show Profile  Reply with Quote
No, no, you can easily let the Wifi module work as a server and access the Geiger counter via a TCP port. But this must be set up in the firmware of the Geiger counter. If the Geiger counter sends data via a smartphone hotspot to the world map server, it is already connected to its own WLAN and gets a unique internal IP address. Thus, a smartphone app would have access to the WiFi Geiger counter module. Bluetooth is another story and meaningless if the wireless connection is already available anyway. Bluetooth is more for children, because the range is just a stone's throw. WiFi is strong enough and above all already installed and in operation. So it's just a software matter.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #20

ZLM

1241 Posts

Posted - 10/20/2019 :  20:09:20  Show Profile  Reply with Quote
I agree with Geo-Johnny s point. The Wifi is a much advanced connection than bluetooth. The bluetooth only for short distance communication.
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Reply #21

ullix

Germany
418 Posts

Posted - 10/20/2019 :  22:38:49  Show Profile  Reply with Quote
@ZLM:
quote:
The bluetooth only for short distance communication.


Really?
WiFi goes up 100m. Bluetooth goes up to 100m. Which of the two is shorter?
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Reply #22

Geo-Johnny

Austria
154 Posts

Posted - 10/20/2019 :  23:33:40  Show Profile  Reply with Quote
Bluetooth

And why should one convert to Bluetooth, if a good WiFi module is already installed and in use? Unfortunately, only a small function is used at the moment, the module itself offers much more potential.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #23

Damien68

France
58 Posts

Posted - 10/21/2019 :  06:30:25  Show Profile  Reply with Quote
@Geo-Johnny:
my god, I'm over 50, I withdraw what I said about Bluetooth, it's true that it go no more far than a baby park :-)

@ullix:
Bluetooth Class 1 is +20 dBm (100mW) RF output power and can be received at 100m
Most android smartphones and most Bluetooth devices are Bluetooth Class 2 or 3 and can therefore be received between 1 and 10m
For iphones I do not know exactly but Bluetooth Class 1 is outside his field of application and is very rarely used
h**p://bluetoothinsight.blogspot.com/2008/01/bluetooth-power-classes.html

Wifi vs Bluetooth, it depends on the applications, but it is true that we are not there to make a specification.


Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 10/21/2019 07:45:13
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Reply #24

Geo-Johnny

Austria
154 Posts

Posted - 10/21/2019 :  09:12:25  Show Profile  Reply with Quote
quote:
Originally posted by Damien68

@Geo-Johnny:
my god, I'm over 50, ...

Welcome to the club, i am 58+.

And now the end with the Bluetooth discussion. Bluetooth is only for kids to listen to music and play games.

We need a good app on the smartphones for the GMCs, thats it.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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Reply #25

Stargazer 40

USA
346 Posts

Posted - 10/21/2019 :  13:11:58  Show Profile  Reply with Quote
I have two HVAC thermostats that I get readings and control heat, ac, and blower with a phone app. The thermostats connect to my wifi and the phone app picks up data from the internet. The thermostat maker acts as server and I pay a small fee for each per year. I like the local, internet free Bluetooth approach that works between my Fitbit and phone app, but also like getting readings across the internet when not at home from my thermostats (and controlling them).

As a parallel my CDV-717 ionization chamber survey meter allows the base to be separated from the meter with a 25 foot cable. This allows the detector to be placed outside a shielded area to monitor activity without exposure. I like that aspect of remote measurement and think that certainly would likely be in the 1-10m range making Bluetooth viable.

Stargazer 40

Edited by - Stargazer 40 on 10/21/2019 13:53:16
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Reply #26

Damien68

France
58 Posts

Posted - 10/21/2019 :  23:34:56  Show Profile  Reply with Quote
if there are containment walls, it can drastically reduce the range of wifi and bluetooth.

Mastery is acquired by studying, with it everything becomes simple
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Reply #27

ullix

Germany
418 Posts

Posted - 10/22/2019 :  01:46:22  Show Profile  Reply with Quote
As Damien has already pointed out, there are multiple classes of Bluetooth, which basically determine the energy consumed by the device. And lastly the power available to the device determines the range.

So it is not the technology per se, but the design decision, which determines range. Both technologies are equal in potential(!) range. The lower range of certain devices is by design, not by technical possibility!

WiFi power can also be restricted by design, and further might be impacted by the legal situation, permitting power only within certain limits.

Confusing the matter, Bluetooth is available as the "Classic" Bluetooth, or as the "BLE" (Bluetooth Low Energy, BT version 4).

The Classic is more suited for a steady stream of data (like music sent to earphones), while BLE more to chunks of data. A Geiger counter application is suited for BLE.

If low energy consumption - like wanting long lasting batteries in a mobile Geiger counter - is a wish, you want to go BLE, and also limit power consumption, hence thereby also limiting range.

But programming BLE is a whole lot more complicated than either classic BT or WiFi. GeigerLog can communicate with devices by WiFi; it is easy and actually is already implemented.

I am now working on a project coupling GeigerLog to a BLE device. Well, that is a real challenge...

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Reply #28

Damien68

France
58 Posts

Posted - 10/22/2019 :  07:05:01  Show Profile  Reply with Quote
Hi Ullix, welcom to BLE world, BLE is one of my specialties too (hardware in my case and low level device chipset software).
as you say it is a challenge, there is a lot of things to assimilate. With my colleague (for the software) we had to put 10 months to release our first complete system from scratch (home automation) .
As you say BLE is no worse of Wifi, and largly better for low bitrate devices.
BLE having a much narrower bandwidth, his receiver have therefore much more sensitive nature, and for the same power of émission, it carry therefore more far.
The difference in receiver sensitivity between the two (Wifi(bgn) vs Blutooth 4) is about 13 dB this is a power ratio of 20. it marks a first difference.

the principle of BLE is to spend time to wake up and sleep synchronized with the access point. after connected, each device has a periodic time slot during which it must be woken, otherwise he can sleep. During sleep time is totaly frozen, only a wake up timer remain active. It is the first fundamental principle of BLE

So keep connection active with wifi draw minimum of 70 mA on battery as long as the connection is active.
With the Blutooth, it is more arbitrary and parametrable.
Some devices powered with 220mAh coin cell maintain an open connection up to 3 months this gives an average current of 0.3 mA (200 time less than Wifi)
Other Bluetooth home automation devices can hold up to 10 years on the same 220 mAh battery, but they do not make physical connection and just send advertising
It marks a second difference.
Afterwards, if a device is not connected and is trying to connect, then it consumes a lot more, but, less than Wifi. that's why in general you have to press a button to make a connection request.

BLE data flow is limited, his data packets are limited to maximum of 27 or 251 Bytes (depending on the BLE version)
But it's true that BLE seems optimum for a connection between a meter and a phone.
But if you want for example multiple simultanous opened connections (many devices connected to the meter), with Wifi you can have many sockets opened in same time, with BLE this is not possible unless if it's the meter that act server, but it's becoming perverted.
With lasts versions of BLE you can share device with multiples server, but limited to only one connection active.

Otherwise, to return to the USB connection, I did a quick test by conecting a 500+ on the USB connector of a Nexus 5X with a USB Ampere-meter / volt-meter.
During my tests, at boot time the meter has to consume up to 150mA on the USB port of the phone, after boot it consumes less.
150mA for some telephones can be already too much, I can not say too much whether it is correct or not, but I do not feel it.
For a PC connection, this is not a problem

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 10/22/2019 07:43:20
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Reply #29

ullix

Germany
418 Posts

Posted - 10/22/2019 :  23:26:54  Show Profile  Reply with Quote
@Damien: good to know what you are up to! Would you mind if I contacted you when I have some BLE questions?
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Reply #30

Damien68

France
58 Posts

Posted - 11/12/2019 :  13:08:58  Show Profile  Reply with Quote
@Geo-Johnny:
About LND-712 (I just ordered one in germany), why we don't put the tube in a lead pipe, this would reduce the background noise of the tube, and should not affect the sensitivity of the tube in front of its window.
it could make it possible to increase the Signal / Noise ratio in case we want to measure small levels of radiation. I'll do tests when I get it
Also we could place a complete wand like the Stargazer40 one in a lead tube, this in the same way guarantee the necessary cathode electrical insulation.
Image Insert:

112074 bytes

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 11/12/2019 13:35:37
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Reply #31

Geo-Johnny

Austria
154 Posts

Posted - 11/12/2019 :  14:05:18  Show Profile  Reply with Quote
@Damien68

I already had the idea with the lead pipe. But I wanted to make it movable and changeable. A lead pipe and an aluminum pipe. Then you can filter out with aluminum beta rays and with the lead pipe the background radiation. For the front window, I've considered the same thing with removable discs.

Geiger Counters: GMC320+V5 & GMC500+
Geiger Tubes: M4011; SI-3BG; SBT-9; LND712; SBM-20
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