simple way to add analog meter to this?

Discussion in 'General Electronics Chat' started by BillRush5, Feb 10, 2013.

  1. BillRush5

    Thread Starter New Member

    Jan 13, 2013
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    Enclosed is a simple Geiger counter circuit that I have been using for some time with small tubes. I wonder if it's possible to easily add an analog meter to this and what would the schematic/ components be? Thanks in advance, Bill
     
  2. crutschow

    Expert

    Mar 14, 2008
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    You would just connect the meter in series with the Geiger tube.

    Do you know what current value you want to measure?
     
  3. #12

    Expert

    Nov 30, 2010
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    It looks to me like 400ua is the max, assuming the voltage is really 900 volts and the geiger tube is completely saturated. That means the real current is a lot less than 400ua. Can you buy a meter that will operate in that range?
     
  4. crutschow

    Expert

    Mar 14, 2008
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    50μA full-scale analog meter movements are quite common.
     
    #12 likes this.
  5. BillRush5

    Thread Starter New Member

    Jan 13, 2013
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    It's really that simple, guys? Just adding a small meter in series with the beeper? And the meter will move upward as more and more events are received?

    IIRC, someone asked this question in another place somewhere and the response was adding a timer and then an IC to drive the meter but if I can truly keep things this simple, that's my goal. I will give this a try soon. Thanks for your responses!
     
  6. crutschow

    Expert

    Mar 14, 2008
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    The problem may be, how many events per second you will see and what the average current actually is. If they are below the time constant of the meter inertia then you may only see little blips on the meter, rather than a steady reading. A capacitor across the meter will help integrate the pulses and give a more steady reading, if that is the case.
     
  7. Jaguarjoe

    Active Member

    Apr 7, 2010
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    If you put 400uA through a 50uA meter, you will be overloading it by a factor of 8. My last employer handled my workload the same way and I gave up. The little meter might do the same.
    Add a small trimmer resistor across the meter and you can tweak it for 90% deflection or so.
     
  8. #12

    Expert

    Nov 30, 2010
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    I'm thinking, "If you measure enough radiation to saturate that tube, you're going to forget about electronics and change your priorities to funeral planning".

    Still, a shunt across the meter won't hurt anything. The buzzer will notify you of events that you would never see on the meter. The meter will only provide a useful reading when the buzzer is mostly "on".
     
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