Oscope Question

Discussion in 'General Electronics Chat' started by kuch128, Sep 26, 2012.

  1. kuch128

    Thread Starter Member

    Mar 7, 2011
    20
    1
    Hello all I recently bought an oscilloscope from Saelig the DS8102 with 100MHz bandwidth and 2GSa/s but I think I am beginning to run into a problem but I am still unsure if it is operator error or something wrong with the scope. First let me say that when I use the scope's test point which is a 5Vpp square wave at 5kHz the scope measures it perfect. (Here is the part which may seem childish) When I was playing around with the probe I noticed that is was giving me a perfect (well almost perfect) sine wave at 60 Hz at nearly 12Vpp when touching the probe and when I plug in a DC power supply into the same outlet it jumps up to nearly 18 Vpp even when the power supply is off. What I am thinking is that there may be an issue with the outlet itself and not my scope. I hope I am not overlooking something stupid but that is why I come to you all to maybe show me error in my ways.
     
  2. CVMichael

    Senior Member

    Aug 3, 2007
    416
    17
    Did you attach the ground wire (alligator clip) of the oscilloscope probe to the ground of your device?
     
  3. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    Some power supplies, employ "bleeder" resistors in the filter capacitance, some do not............
    You may be measuring the residual charge left on components in the supply.
     
  4. kuch128

    Thread Starter Member

    Mar 7, 2011
    20
    1
    I "measured" myself with and without the alligator clip applied to the test point ground no difference also im still getting the sine wave with or without the power supply plugged in. I also walked around the house testing other outlets same thing.
     
  5. ifixit

    Distinguished Member

    Nov 20, 2008
    639
    108
    Hi kuch128,

    If you are just connecting the probe tip to your body, then it is normal to see alot of 60Hz on the display. Your body acts like an antenna and picks up the EM from electric devices close by. There is not much energy in these signals, but because your scopes input impedance is 1 Megohm, it doesn't take much energy to display a EM signal in this maner.

    Have fun with your new scope,
    Ifixit
     
  6. kuch128

    Thread Starter Member

    Mar 7, 2011
    20
    1
    Thank you thank make sense I was just throw off by the clarity of the wave and its amplitude I haven't seen anything like that with the other scopes I used.
     
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