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Anyone near Rotherham who could test my Scope?

Discussion in 'General Electronics Chat' started by bigal_scorpio, Aug 10, 2008.

  1. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Al,
    Look at this link 50R versus 75R bnc's
    http://en.wikipedia.org/wiki/BNC_connector

    Extract:
    Specifications

    BNC connectors exist in 50 and 75 ohm versions. Originally all were 50 ohm and were used with cables of other impedances, the small mismatch being negligible at lower frequencies. The 75 ohm types can be recognized by the reduced or absent dielectric in the mating ends. The different versions are designed to mate with each other,[1] although the impedance mismatch will lead to signal reflections. Typically, they are specified for use at frequencies up to 4 and 2 GHz, respectively.

    NOTE. The physical sizes of the 50 and 75 ohm sockets are slightly different and can damage the "wrong" plugs.
     
    Last edited: Sep 3, 2008
  2. bigal_scorpio

    bigal_scorpio Active Member

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    Scope Test

    Hi Eric, Nigel and all,

    The scope is working to some extent, but I'm puzzled about something.

    I have made a small square wave generator that can go from 1hZ to 100khZ in decades. When I measure the wave I only get the horizontal lines you see in the picture I took. I always thought and expected to see the whole wave, that is an unbroken line made from vertical and horizontal sections!

    The square wave was set at 100hZ in the picture. As to the settings of the scope I am puzzled as the Time/CM knob has 1 to 50 uS, 1 to 5 mS and 1 to 100 ?S So I don't actually know what the three sets of numbers denote, as I said two are marked up but the third is baffling me!

    Eric, you have a HiRes picture of the controls, could you clarify for me?

    Anyway let me know what you think of the result, and thanks for all the help guys, it's really appreciated :)

    Al - may change my nick to BigAl_Scopio hehehe
     
  3. Mikebits

    Mikebits Well-Known Member

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    You should convert Frequency to time. The formula is 1/frequency, or in your case
    1/100Hz = .01 sec which is 10ms. So to see 1 cycle you would set your time/div to 1ms (This is because graticle is 10 divisions 1ms each) With scope set to 5ms/div you would see 5 cycles, assuming you indeed are measuring 100Hz. See attached pics.

    If you still see no waveform make sure your volts/div is like 5v, also verify your waveform gen is working.
     

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    Last edited: Sep 3, 2008
  4. dave

    Dave New Member

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  5. Mikebits

    Mikebits Well-Known Member

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    Here are some link for scope tutorials.

    http://oscilloscope-tutorials.com/
    This next site is real cool, it is a virtual scope. You can change all the settings and stuff.
    http://www.virtual-oscilloscope.com/
     
  6. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Al,
    The TIME/CM control sets the speed of the spot that produces the trace on the scope screen.
    The visible bright spot moves across the screen from left to right, the spot is blanked [set dark]
    and quickly flys back to left side of the screen.

    When the TIME/CM is set to 1uSec, this means the spot travels 1cm/uSec from left to right,
    so with a scale of 10cms it would take 10uSec to move to the righthand side of the screen.

    In order to see a 100Hz input signal on the YA or YB inputs, set the TIME/CM to 10mSec,
    this should give 10 square waves across the screen.

    If you now set the TIME/CM to 1mSec you will only see 1 square wave.

    In cases where you are not sure of the waveform frequency you are scoping,
    just click the TIME/CM around until you see a recognisable waveform.

    By knowing the speed of the trace spot and noting the peaks/troughs in the waveform
    you can work out its frequency by counting cms at that TIME/CM setting.

    OK.?:)
     

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    Last edited: Sep 4, 2008
  7. on1aag

    on1aag New Member

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    Hi Bigal scorpio,

    I think I know what you mean.
    You can't see the vertical step because the step is too
    steep with respect to your timebase setting. Very few
    electrons reach the same spot of your screen with respect
    to the distance the trace traveled.
    The only thing you can do is increase the intensity (a bit).
    The top trace was the input signal from a function generator
    (I think), If you look more closely you can see that there
    is something visible. The bottom trace is a mosfet switch,
    it switches on very rapidly but needs more time to switch
    it back off. You can clearly see the difference in intensity.
    The dimmer a trace is the more quickly it moves on your screen.

    [​IMG]

    on1aag.
     
  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi on1aag,
    Nice clear pic and description.:)

    I think my christmas dinner is no longer on hold.;)

    Regards

    EDIT:

    Added the 'missing' fast invisible edges on1aag image, to show the ideal scope trace.

    Hope you don't mind on1aag.:)
     

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    Last edited: Sep 4, 2008
  9. bigal_scorpio

    bigal_scorpio Active Member

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    My scope

    Hi Guys,

    Do I feel stupid or what! The THREE sets of voltages I mentioned are only two! I never noticed the decimal points before! DOH!

    Anyway thanks forn all the input guys, its made me feel a lot happier about the scope. on1aag was right about my concern and Erics photo retouching was the clincher, thats what I was expecting to see and never having the scope working properly before it made me wonder if it still had a problem, but thats all sorted now. :)

    Next thing I am hoping to try is looking at a sine wave, its why I got the scope in the first place and I could never get one on it. Now that its working properly I would like some suggestions of what to check so I could see some nice sine waves. So any ideas on what I could test that would be definately outputting a decent sine wave?

    I want to take any possibility of the wave being the wrong type out of the equation, once I have seen a sine wave on my scope I will be truly happy and content to test things and know that what I am seeing is true.

    So if any of you know of a good source of sines please let me know whether it involves making something or just measureing an everyday object I don't mind. :)

    Thanks again guys :) .........Al
     
  10. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Al,
    That ESR Wien osc output should a good sinewave.
    I would like to know what you get.

    also a low voltage mains transformer, say 5V thru 24V would give a 50 Hz sine.

    Connect a microphone, set it to 5mV/cm and you should see your voice.


    EDIT:
    try these two common type of circuits
     

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    Last edited: Sep 4, 2008
  11. bigal_scorpio

    bigal_scorpio Active Member

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    Sine waves!

    Hi everyone,

    Just tried the scope on a small 12v AC transformer and have finally seen a true sine wave on my old but reborn (thanks to Eric, Nigel and everyone who helped) Scopex Oscilloscope! The graticule was gratifying. :)

    I can't thank all who contributed enough.

    Just one final question, is it acceptable to use a scope stood on its back stand, or is there a reason that it should be used close to horizontal?

    Thanks again to all..........Al :D
     
  12. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    It's OK any direction.

    And well done again Al! :D
     
  13. Mickster

    Mickster Well-Known Member

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    I've watched this thread from the very start, unable to offer anything myself.

    It's great to see the scope working and the selfless help that has been offered by all those involved, to get it to this state.

    Well done Guys.
     
  14. bigal_scorpio

    bigal_scorpio Active Member

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    Sine Waves!

    Hi Eric, Nigel and all,

    Just the pics of the sine wave on pin 1 of IC1 on my (Nigels) ESR meter, as requested by Eric.

    1st pic is scope on with no sigal, 2nd is the long lost sine wave :D and pic3 is the settings it was on.

    That sine wave sure is a beautiful sight and I would never have got it but for the generosity and help from you guys!

    Thanks again...............Al

    BTW at last I feel like I've accomplished something, and now I can get into another project thats been on my mind for months! I am certain I will yet again need help on it but I will start a new thread as it's a totally different subject :)
     
  15. bigal_scorpio

    bigal_scorpio Active Member

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    Hi all,

    I just figured out why the wave wasn't centralised! I had the clip on -9v instead of 0v! :eek:

    Oh well I suppose I'm learning anyway hehehe.

    Al
     
  16. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Al,
    They are very small pics.?:p

    BTW: Dont have the trace spot very bright on slow X scan speeds it could put a burn mark on the tube phosphor.

    Bring on the pics.!:)
     
  17. bigal_scorpio

    bigal_scorpio Active Member

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    Hi eric,

    Just realised that the wave I'm getting is only 0.5v P-P!

    The author mentions 5v P-P but that is when testing with the MM, is the scope test in a different place?

    Am I measuring the output at the right place? Clip on 0v (between batteries) and probe on pin 1 IC1.

    Is this correct?

    Al
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Do you have your scope probe set to x10?, that would give you 0.5V instead of 5V.
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi Al,
    Whats the battery voltage.?
    Where are you measuring the wave.?

    Do you have the probe switched to *10 ?

    What setting is the YA amp on.?

    Didnt have any pictures on your earlier post.
     

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    Last edited: Sep 6, 2008
  20. bigal_scorpio

    bigal_scorpio Active Member

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    Hi Eric,

    I'm a complete ^%^%$^^&!

    You were of course quite correct :eek:

    These new fangled gadgets take some getting used to! ;)

    Al
     
  21. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Im not sure what a complete ^%^%$^^&! is so I had better keep quiet.:rolleyes:

    Where are the pictures... ?
     
    Last edited: Sep 6, 2008

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