Oscilloscope probes does it matter what the frequency is?

Discussion in 'General Electronics Chat' started by bance, Oct 25, 2012.

  1. bance

    Thread Starter Member

    Aug 11, 2012
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    Hi guys,

    I bought an old Leader 20mhz analogue scope on E-Bay, it's 2 channel but only came with 1 probe. I was considering buying another probe so that I can use both channels. I see them for sale, often listed by frequency, does this affect the readings?
    I understand they have to have the correct impedance but frequency?

    Thanks for helping a 'noob'
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The probe to buy must fit the input impedance and capacitance.
    Some times there is given X MΩ / X pF.

    Bertus
     
  3. bance

    Thread Starter Member

    Aug 11, 2012
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    34
    Thanks Bertus,

    I had a feeling that the frequency quoted didn't matter since it's the scope that does the work and not the probe!
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    When the frequency range of the probe is equal or greater and the impedance is right, it should work.

    Bertus
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    3,353
    Why spend extra money for a higher frequency probe when you don't need it?

    Here are a few things you should know about probes.

    Since your scope is 20MHz, which is relatively low by today's standard, maybe you don't even need a probe. A simple coax cable with a BNC connector on one end and alligator clips on the other will do fine for audio frequency testing and microcontroller debugging.

    [​IMG]


    If you are looking to purchase a proper probe, get one that is a 10x attenuation probe or one that has a switch selectable 1x and 10x.

    When I use a probe, I always use it on the 10x setting. This increases the input impedance of the measuring system from 1MΩ to 10MΩ and it extends the bandwidth.
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
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  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    The frequency rating of the probe tells you it's usable bandwidth, the higher the better. Obviously, if your scope is only 20 MHz, a probe with 100 MHz bandwidth is better than you need but no problem.

    There were a few super scopes like the TEK 7904A that had bandwidths of about 275 MHz so the probes had to be super wide band to not compromise the performance of the scope itself.
     
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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  9. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I bought two sets off ebay. They seem to work perfectly with my TEK465. The compensation adjusts properly and the square waves look sharp edged.

    They are cheap made in China, but they work.
     
  10. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    I have them too. They seem to fit my needs.

    But I think you did a little better on price.
     
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