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DIY HV CRO probe

Discussion in 'Electronic Design' started by Larry Hirsch, May 15, 2006.

  1. Larry Hirsch

    Larry Hirsch Guest

    What would be the most cost-effective way to protect my Tektronics TDS
    digital oscilloscope from possible damage by 2-3KV audio signals? It
    is rated for 300VAC input max.

    I don't need to measure the frequency or voltage, only check the
    waveform for distortion without blowing my CRO.

    Regards,

    Larry
     
  2. Klaus Bahner

    Klaus Bahner Guest

    What would be the most cost-effective way to protect my Tektronics TDS
    High voltage probe?

    Klaus
     
  3. On Tue, 16 May 2006 07:08:32 +0930, in sci.electronics.design Larry

    possible damage by 2-3KV audio signals?

    where do you get 3KV audio from these days?
    Are DVDs 32 bit audio yet?



    martin
     
  4. Pooh Bear

    Pooh Bear Guest

    You could always make a voltage divider I suppose. Probably be fine for just
    audio.

    Farnell sell a 100x probe for a little over £20.

    Graham
     
  5. Ian Stirling

    Ian Stirling Guest

    It's only a megawatt into 8 ohms :)
    There are electrostatic speakers popping up on ebay fairly regularly,
    most in need of repair.
     
  6. Robert Baer

    Robert Baer Guest

    Pray tell where the heck would you even GET 1KV (or larger) audio
    signals????
    And hypothetically speaking, if you had such a source, would you be
    so ignorant or s*d to connect it to the scope?
    Would you connect the AC line to your VOM set on ohms?
    Would you step in front of a train going 60 MPH toward you?
     
  7. tekamn

    tekamn Guest

    Buy a 100:1 divider probe from Hameg or Farnell. Price is approx. 40 to
    60 USD, which is acceptable considerign the costs for a Tek scope.

    DIY is possible (check e.g. Sam Goldwasser sites for ideas how to do
    this), but I would not recommend to risk my health on a DIY probe when
    a commercial, tested and approved probe is so inexpensive.

    The Hameg is save for 2.5 kV guranteed, if you need higher ratings go
    for a used Tektronix P6013 (up to 12 kV) or 6015 (up to 40 kV).


    hth,
    Andreas
     
  8. Tim Auton

    Tim Auton Guest

    Obviously not, hence the question. Dumbass.


    Tim
     
  9. GregS

    GregS Guest

    For one time projects it hardly makes sense to buy a probe. About
    a dollars worth of resistors will work. I usually wire 1/4 watt
    carbon resistors with a max of 300-400 volts across each in series.
    Long term voltage across these requires splitting up the voltage,
    but for short term work, the voltage could be increased a bit.
    If one can't figure out the entire rig, I would buy a probe.

    greg
     
  10. GregS

    GregS Guest

    The requirment didn't mention frequency response, so some simple
    audio should not be attenuated by much, since there is no compensation given here.

    greg
     
  11. ehsjr

    ehsjr Guest

    You can use a turkey baster as the probe body. I did it years
    ago. I rolled the resistor string in mylar from an art supply
    store. I don't remember now how many layers for sure - I think
    it was 11. Damn good insulation. At the probe end and the top
    I used RTV to hold the probe wire and the jack. The probe was
    end just a resistor lead.

    Ed
     
  12. tekamn

    tekamn Guest

    Hi Greg,

    Most DIYers think that it hardly makes sense to buy the the right probe
    right away. Soem of them noticed that it was the wrong decision - the
    last thing the note in HV applications.

    It's okay to build a HV probe for yourself, as Sam Goldwassrs points
    and the same recipe you give. As long as you have enough HV experience
    and you *know* where the critical points are, that is okay.

    But the OP has spend money for a Tektornix TDS DSO, which is not a
    cheap instrument. So I guess there he has a little bit of money left to
    do things right the first time. Keeps him healthy and the scope too.

    just my 2cts of opinion, YMMV.

    hth,
    andreas
     
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