O probe query

Discussion in 'General Electronics Chat' started by Canobi, Mar 5, 2015.

  1. Canobi

    Thread Starter New Member

    Mar 4, 2015
    Hi all

    Ok, so I realise I'm tredding old ground here, but I've spent quite a bit of time trawling the interweb looking for any and all info on selecting the right probes for a second hand O scope. While most of the info is there, some of it is still lacking detail which I'm hoping someone here might be able to help clarify.

    From what I've gathered so far, the probes impedance have to match that of the scope (1Mohm to 10Mohm), and ideally work at twice the frequency of the scopes capability.

    The part I can't find any detailed info on is probe attenuation Vs scope input capacitance matching.


    As seen in the details above, the scopes input capacities range from 5nf to 30nf.

    So, does this mean I have to find probes that has a 5nf to 30nf attenuation range, or can probes that have nf values that overlaps part of the scope range be used (ie a 15nf - 45nf probe giving an attenuation range of 0 - 15nf if we regard the probes min setting as 0 in this case)?

    The closest I've seen are a pair of cheap chinese 1X - 10X 8nf - 35nf, most start around 10nf to 15nf as far as I can tell.

    I know little about operating, or the who's who of o scopes (yet), but the name cropped up quite a few times during my research and seemed well regarded.

    The scope in question is a Leader LS1021 20Mhz I got from ebay for £80 (manual included). As a double bonus I found a PDF of the sevice manual as well.

    It also looks like the company still partially support some of their old models (ie documentation, repair/calibration service) which is good sign, shows they have confidance in their products.
  2. bance


    Aug 11, 2012
    The capacitance values range from 25-35 pico-Farads (30-5/30+5) that is a long way from nano-Farads.;)
    15nF-45nF would give a range of 30nF, however one would regard 15nF.
    In answer to your question, if you can excuse my pedantry, any probe that has the correct impedance/frequency rating and can be adjusted for the correct input capacitance will be fine. 8pF-35pF or 10-15pF to 45pF both cover the range your scope requires.
    I have a Leader 'scope and they are very good instruments indeed, I wish you much fun and learning with your "new" 'scope.

    HTH Steve.
  3. Canobi

    Thread Starter New Member

    Mar 4, 2015
    Thank you for clearing that up for me, I hadn't noticed it was pf on the probes (duh!).

    Yeh, looking forward to it :) I'm hoping it'll help with designing some EL inverters I have planned.