No signal from my geiger tube

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Loynis
Posts: 2
Joined: Thu Apr 19, 2018 11:58 pm

No signal from my geiger tube

Postby Loynis » Fri Apr 20, 2018 1:01 am

Hi everyone,

I've seen that some of you are experienced with geiger tubes, could someone help me plz ?

I bought a geiger tube (CTC-5) some weeks ago and tried to connect it properly:
I downloaded the datasheet and made my own circuit:

I'am using a 4.5V battery, which is boosted to 5V then to 380V;
then i connected a 6,8 Mohm resistor (R1), my geiger tube, then a 100k resistor (R2) and back to the ground.

With an oscilloscope, i checked the signal between R2 and the ground: where i should get sometime 5V , i have nothing.
I tried to replace short-circuting my tube by connecting R1 to R2, and then i get my 5V signal.

I tested my circuit with another tube, and i still have the same problem.

Is there something wrong i'm doing ?


Thanks,

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mightyohm
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Posts: 975
Joined: Fri Apr 03, 2009 10:29 pm
Location: Seattle, WA
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Re: No signal from my geiger tube

Postby mightyohm » Sat Apr 21, 2018 10:16 pm

Have you verified that your high voltage supply is working and the voltage is correct?
Do you have a radioactive sample for testing or are you relying on background radiation?

Loynis
Posts: 2
Joined: Thu Apr 19, 2018 11:58 pm

Re: No signal from my geiger tube

Postby Loynis » Sun Apr 22, 2018 9:58 pm

Yes, i checked my voltage (i had to adjust it) with 2 different multimeters.
Is there a chance the current is too low ?

I used a radioactive source, but nothing more happenened.
I borrowed a SBM-20 and nothing happened too: I'm desperate :'(

Any other way to check if my tube is functional ?

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mightyohm
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Posts: 975
Joined: Fri Apr 03, 2009 10:29 pm
Location: Seattle, WA
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Re: No signal from my geiger tube

Postby mightyohm » Mon Apr 23, 2018 9:47 am

Check out my Geiger counter kit: http://mightyohm.com/geiger

I sell a minimal version of the kit that includes a high quality PCB and all electronic components needed to build the kit. You can supply your own case and SI-3BG, SI-1G, SBM-20 or CTS-5 Geiger tube.
It would be useful to have this kit as a "known good" circuit for testing, and if you have any problems with the kit I can provide support.


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