Signal conditioning Best Practises

Discussion in 'The Projects Forum' started by Hybird, Apr 21, 2011.

  1. Hybird

    Thread Starter New Member

    Jan 5, 2011
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    0
    Like the title says. I'm trying to get a fairly unmanageable signal to a digital logic level. Below is the schematic of the detector, it is a gamma detector built from a Geiger tube and High voltage source.

    [​IMG]

    So what happens is a gamma ray hits the tube and it acts as a short circuit temporarily. This causes the capacitor which is charged to some high voltage to drain off its voltage through the Geiger tube and hence you see a small dip in the voltage on the cap which is our signal.

    How would you go about constraining this signal to fall between 0-5v ? I have been thinking about doing it with diodes. Is there any other way to do this? To me it seems like it has potential to consume a lot of current, and this is to be a low current device (works on small battery).

    Is there any reference to this type of signal conditioning that I should know about, or perhaps insight on how others might do it?

    The way I was thinking is tie the signal to a diode and the other end to the 5v supply rail, so as soon as the cap goes >5v it will forward bias the diode and pin the voltage to a max of 5. But would this require a series resistor with the diode? I mean one side could be at 70 V and the other is pinned at 5v so that makes a short doesn't it?

    Thanks in advance.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
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