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Measure a higher voltage than my O-scope can handle

Discussion in 'General Electronics Discussion' started by plukens, Jun 2, 2012.

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  1. plukens


    May 23, 2012
    This question seems so simple, I’m sorry to have to ask it….

    I am driving a liquid droplet generator with a low frequency (100 Hz or less) square wave produced by my HP 214B pulse generator. I wish to monitor the signal with my oscilliscope at the same time. However, I cannot go above 30V peak because that is the input limit of my O-scope. I wish to go as high as 100 V, which is what my signal generator can produce. What simple device can I buy to reduce the voltage to my O-scope by a factor or 2, or perhaps 5 or even 10?

    I have a x10 probe for the scope, but it has a sharp pointed tip. I need one with BNC connectors on both ends.

    Something I can buy cheaply is the goal, perhaps on ebay. Making a voltage divider with resisters is my second choice.
  2. shrtrnd


    Jan 15, 2010
    I don't know what they're called, but I have several adapters I got with a LeCroy differential amp. The adapter plugs into the (scope) probe, and the other side of the connector fits
    into the BNC connector. So they're out there, you just have to look for them.
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Why is a voltage divider your second choice? Even a x10 or x100 probe is fundamentally nothing more than a resistive voltage divider (with high precision plus added capacitors for trimming the frequency response).

    Assuming you scope has 1MOhm input impedance, adding 99MOhm in series will do the job.

    If you can't get 99Mohm, use a similar value - you can correct the measurement error by calibrating the setup or simply computing the deviation from the ideal divider ratio due to the resistor's mismatch.

  4. plukens


    May 23, 2012
    Thanks for the input. Making a device is my second choice. I'd prefer to buy something. If there is an inexpensive stock part I can purchase from DigiKey or on Ebay, that would be ideal.
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    It's almost a LMGTFY moment honestly.

    Look here.

    And sure, you can find the same things cheaper on ebay and other sites which source stuff direct from China. Of course you need to exercise some care because if it can't handle the voltage it may be your scope or worse (you) that get killed.
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