Anyone know how to test a geiger circuit/tube?

Discussion in 'General Electronics Chat' started by doug08, Aug 17, 2011.

Thread Status:
Not open for further replies.
  1. doug08

    Thread Starter Member

    Jan 30, 2011
    153
    2
    I made this circuit and added one extra voltage multiplier to get the higher output voltage I needed, I also switched the schematics 10M anode resistor to 1M as per the GM tube spec sheet:

    http://www.galacticelectronics.com/GeigerCounter.HTML

    I'm using this 700v tube with the following specs instead of the schematics 500v tube: USN-5980 /beta-gamma/ operating volts 660-800 / Recommended operating voltage 700V/ start up voltage 640V / anode resistor 1M / tube capacitance 3pf.

    The circuit works, I can hear the HV circuit whining softly and the voltage is adjustable from 485V to 760V. With my high quality DMM I get 700VDC BEFORE the anode resistor, and 425V after the anode resistor. Is this normal? I know you'll get a drop, but is that a normal drop? Is the drop because of the DMM impedance? Seems like a lot. The circuit will emit a click at varying intervals(4-9 per minute), sometimes a double click. Vaseline Uranium beads have almost no effect. Is there a way to find out if the tube is good? I read something about shorting the tube while in operation to see if you get clicks. Really sucks because the entire thing is completed and looks store bought. It also has a built in low battery LED which I made illuminate when the 9V battery drops to 7.25V. I also added a built in 9V nimh charging circuit made from an lm317t for regulating the charging voltage at 9.65v, and some resistors to lower the charging current down to around 20-30ma. Thanks for any/all help. I have lots of pics of the completed geiger counter.
     
  2. doug08

    Thread Starter Member

    Jan 30, 2011
    153
    2
    Last edited: Aug 18, 2011
  3. MrChips

    Moderator

    Oct 2, 2009
    12,442
    3,361
    You will have to get your hands on a source of gamma-ray radiation. Not an easy thing but still possible. Try the Physics department in most universities.

    The only other thing I can think of is to get a household smoke detector/alarm that has Americium-241 source in it.
    Do not take the alarm apart. Just bring the alarm up close to the Geiger counter.
    I don't know if this will work. I will have to test this and get back to you later, maybe tomorrow.
     
    Last edited: Aug 18, 2011
  4. MrChips

    Moderator

    Oct 2, 2009
    12,442
    3,361
    Ok, I checked. A smoke detector has 1uCi of Americium-241, half-life is 432 years. It puts out both alpha particles and gamma rays. The alphas are what are used for the smoke detection. The gammas are what you will detect with the Geiger counter.

    If you bring the Geiger Counter close up to the source you should get about 5-10 counts per second, compared with about less than 1 count per second for background, depending on the efficiency of your detector. Certainly an appreciable difference that you can tell if yours is working.
     
  5. Junaid Hussain

    New Member

    Jan 29, 2015
    1
    0
    I want Geiger tube can anyone help me out,
    I am from India
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,442
    3,361
    Do not hijack someone else's thread. Please start a new thread.
     
Loading...
Thread Status:
Not open for further replies.