Two GM tubes in parallel for max sensitivity

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Home &rsaquo; Forum &rsaquo; Hardware &rsaquo; Two GM tubes in parallel for max sensitivity This topic has 7 replies, 2 voices, and was last updated 6 months, 1 week ago by R_A_Ghosh. Log In Register Lost Password Viewing 8 posts - 1 through 8 (of 8 total) Author Posts December 20, 2025 at 2:47 pm #30105 R_A_GhoshParticipant How to connect two gm tubes in parallel for increase sensitivity….. Any schematic? January 5, 2026 at 10:40 am #30172 uRADMonitorKeymaster We did tests with many GM tubes in parallel. Here is one example: https://www.pocketmagic.net/city-air-quality/ This increases detector capacity, so what you need to do is to adjust the compensation capacitor. It is explained here: https://www.uradmonitor.com/compensation-capacitor/ January 5, 2026 at 10:56 am #30174 R_A_GhoshParticipant What I did is to use an hvdc and two gm tubes with their separate anode resistors and cathode resistors and their respective compensation capacitor. Created two independent counter channels and finally added the counts per seconds. I used two LND7807 January 5, 2026 at 1:57 pm #30175 uRADMonitorKeymaster Sounds good! What HVDC did you use? Would love to see this setup, do you have pictures? What’s next in your project? January 5, 2026 at 2:34 pm #30176 R_A_GhoshParticipant I used a small ac to ac 230v to 230v isolation transformer for mains isolation. Then used a full bridge diode doubler followed by a 68k 5w resistor in series with 200+200+100 V 5watt zener diodes to get 500V. Extremely low noise than a dc dc converter that disturbed my previous setups …. April 14, 2026 at 11:54 am #30195 uRADMonitorKeymaster Interesting design, simple yet effective. Would love to see it should you post a few pics. April 15, 2026 at 10:35 am #30199 R_A_GhoshParticipant Please see attachment for schematic. I will post image of the setup soon. Small transformer provides necessary isolation from mains though. April 15, 2026 at 10:41 am #30200 R_A_GhoshParticipant check the image Attachments:hvdc-scaled.jpg Author Posts Log In Register Lost Password Viewing 8 posts - 1 through 8 (of 8 total) You must be logged in to reply to this topic. Log In Username: Password: Keep me signed in Antispam 2x(3+4)=? Log In

This topic has 7 replies, 2 voices, and was last updated 6 months, 1 week ago by R_A_Ghosh.

Viewing 8 posts - 1 through 8 (of 8 total)

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December 20, 2025 at 2:47 pm #30105

R_A_Ghosh
Participant

How to connect two gm tubes in parallel for increase sensitivity….. Any schematic?

January 5, 2026 at 10:40 am #30172

uRADMonitor
Keymaster

We did tests with many GM tubes in parallel. Here is one example: https://www.pocketmagic.net/city-air-quality/

This increases detector capacity, so what you need to do is to adjust the compensation capacitor. It is explained here: https://www.uradmonitor.com/compensation-capacitor/

January 5, 2026 at 10:56 am #30174

R_A_Ghosh
Participant

What I did is to use an hvdc and two gm tubes with their separate anode resistors and cathode resistors and their respective compensation capacitor. Created two independent counter channels and finally added the counts per seconds.
I used two LND7807

January 5, 2026 at 1:57 pm #30175

uRADMonitor
Keymaster

Sounds good! What HVDC did you use?

Would love to see this setup, do you have pictures?

What’s next in your project?

January 5, 2026 at 2:34 pm #30176

R_A_Ghosh
Participant

I used a small ac to ac 230v to 230v isolation transformer for mains isolation. Then used a full bridge diode doubler followed by a 68k 5w resistor in series with 200+200+100 V 5watt zener diodes to get 500V.

Extremely low noise than a dc dc converter that disturbed my previous setups ….

April 14, 2026 at 11:54 am #30195

uRADMonitor
Keymaster

Interesting design, simple yet effective. Would love to see it should you post a few pics.

April 15, 2026 at 10:35 am #30199

R_A_Ghosh
Participant

Please see attachment for schematic. I will post image of the setup soon. Small transformer provides necessary isolation from mains though.

April 15, 2026 at 10:41 am #30200
R_A_Ghosh
Participant
check the image
Attachments:
1. hvdc-scaled.jpg
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Viewing 8 posts - 1 through 8 (of 8 total)

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