Signal conditioning Best Practises

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

  1. Hybird

    Thread Starter New Member

    Jan 5, 2011
    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.


    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