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RC time, using a Stop Watch, RC time is longer in time is the capacitor bad?

Discussion in 'General Electronics Chat' started by Billy Mayo, Nov 26, 2013.

  1. Billy Mayo

    Billy Mayo Member

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    I watched that O-scope video today and it has nothing at all what we are talking about. I spent 2 1/2 hours watching too and it shows no examples of him or talking about how to use or give examples on to use the external triggering

    I signed on this Electronics forum because it states no where when you sign up that you have to have a masters degree in electronics , E.E degree or have taken upper division college course in order to ask questions on this forum.

    I have watched a lot of O-scope videos on youtube and I can't find examples of this subject

    The Add mode on the oscilloscope is used when a circuit has multiple channels , so you use the ADD mode to ADD the 2 channels when troubleshooting a circuit that has different channels

    But How does the ADD mode help you troubleshoot circuit's that has different channels with the same waveforms or with different waveforms?

    When you do you use the Invert mode?

    Analog O-scopes on a time base, has a Variable Vernier detent knob, if you click the detent out of calibrate position it puts the time base in a recurrent time base that is not calibrated they say

    So what is the time base variable vernier knob used for?
     
  2. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    So the Add function is just another useful feature. Billy, keep in mind the earliest oscilloscopes were very crude and limited pieces of test equipment. Then one day someone said wouldn't it be nice if if we added lines to the screen and gave it a calibrated sweep? Then another person said wouldn't it be nice if we had not one but two vertical channels so we could compare signals? The oscilloscope is just a tool and over the evolution of the tool features were added making the basic tool more useful. Why a vernier uncalibrated sweep you ask? Maybe I want a single repetition of a signal to fill the 10 divisions horizontally across the screen to compare it to another signal. The same is true when I use a variable vertical. We use the features as needed to see what we want to see.

    As to the oscilloscope itself? While it is a really useful and cool tool it does take time to learn its operation and uses. I believe I have mentioned that. If I could spend an 8 hour day with you, a scope and a few function or signal generators I am sure that after 8 hours of hands on instruction you would have a much better understanding of the oscilloscope in general. However, in a forum we know that isn't possible. While at a glance on the surface the oscilloscope looks to be a simple tool it really isn't. Matter of fact it is only simple to those with a solid understanding of how it works and the more features it has the more complex it becomes. It would be great if you had a scope and a few signal sources like function generators and could sit down and start with the basics and work with a scope. Just doing basic lab exercises. Little by little you will gain an understanding of the tool. Eventually you will master the tool and know how to use it to the best of the tools abilities.

    Most of the circuits you have posted are by modular block pretty simple stuff. However, when we take those pieces and put them together we get a more complex circuit making it more difficult to troubleshoot. This is where we need to start with the basics and work from there. You think some of this stuff is frustrating for you? Hell, electronics also gets frustrating for those trying to help you. :)

    Ron
     
  3. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    We had a wayne kerr (love that name lol) 100mghz analogue to start with, and over time (2 years ish) I sold and saved, now I have a Lecroy 4 channel 4oomHz beast with all the ding dongs on. But When I first started I couldnt even work out how to switch the scope on!
    The video was to give you basics, you think you wasted time, but trust me alot of it will now sit in your brain for later. Somewhere in the comments of that video on you tube, the guy gives an index of what time each subject is in the video, go find the index and keep it. It will be handy.
    To learn my Scopes I started with simple filters and function generator, also a 555 timer was useful, I think my dad has said a few times that there are no short cuts. Only thing I would advise for now, is always make sure the scope is not in 50 Ohm mode, until you know the scope backwards (i learnt the hard way :( ). I dunno if you do this stuff for a job or not, I dont care anymore, sick of getting in trouble for idiots kind of thing. So without being rude can you answer a few questions please.

    Can you read the scope ok on the graticules? Or do you need to use the read out (if it has one)

    Do you have access to a function generator? does not need to be super duper.

    Do you have access to resistors and electrolytic capacitors?

    Do you have the time, motivation and energy to learn scope starting at the bottom?

    As for the ext function, somewhere on EEV blog s a video of Dave using it to make a kind of spectrum analyzer out of the scope, I dont remember many details now, go find it.
    Why you in so much of a hurry? Billy be straight with people.
     
  4. dave

    Dave New Member

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  5. Billy Mayo

    Billy Mayo Member

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    Ron,

    1.) What do you use the ADD mode for when troubleshooting circuits? it's ment for troubleshooting mixer circuits or circuits that have multiple channels either of the same waveforms or different waveforms that are being summed or the difference

    You use the ADD mode and the inverted mode on the O-scope

    2.) There is also a "Delay Time knob" for the Time base , This is used for making what kind of measurements? It's mostly used for RF measurements I think, but you can use it to measure frequency & rise time.

    You compared B waveform with waveform A , using the Alt mode

    So it's just a visual thing to make the waveform fit on to the screen to adjust it and compare it to another waveform right

    Where do you find the O-scope videos on this forum, I can't find them, post the hyperlink to all of them
     
  6. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    please would of been nice! And I get called rude! but ok seeing as you cant be bothered to go look I will spend the next 30 mins getting links for you. But seriously next time say please!
     
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  7. kubeek

    kubeek Well-Known Member

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    The vid is most likely this one
    not much on external trigerring per se, but still a nice video to show what can you do if you try.

    edit: wow it even embeds right here :D
     
  8. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    Thanks I think that was it, Billy goto you tube and find EEVBLOG video's, some are rubbish but there are a few gems, also the scopes video is on you tube, the guy that did it has a channel on there with a few good vids.
    A book I got for Christmas and havnt yet read is, ELECTRONIC TESTING AND FAULT DIAGNOSIS
    second edition by G C Loveday. I get my books online from secondhand bookshops etc, it wasnt expensive probably under £5, I got the book to see if I could help you, but then got peed off with you.
    So please answer the questions i posted!
    What equipment do you have access to and components, IF you answer that I can look through my bookmarks and sort some vids out, BUT totally pointless ,unless I know you have the equipment to hand to copy the vids!
    AND from now on LETS ASSUME you are a complete novice and take it from there, I am also a novice but I can try and help where I can.
    Please start being nice tho, as it winds me up then I get agro. I dont work well with agro, Its a near year tomorrow LETS start it properly from page one ;)
    all the best
    LG
     
  9. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    1. I found this video which explains the add mode fairly well.

    2. Ah yes, the use of a delaying or delayed time base. Remember what I mentioned about features. Knowing what a feature does and understanding it is how we make decisions as to when to use those features, be it the Add mode or Delaying Time Base feature. This video is an example of using a delaying time base.

    Keep something in mind here. These features can vary from scope to scope by manufacturer and model numbers. I try to keep links pretty generic in nature. Hopefully the videos will be of some help. Matter of fact I suggest you try and absorb some of this stuff then using a generic scope try a little practical application on your own like I mentioned earlier. The best way to get a handle on this stuff is practical application. When in a classroom learning this stuff that is what lab exercises are all about, getting hands on experience and watching what you learned work.

    Ron
     
  10. Billy Mayo

    Billy Mayo Member

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    I have already watched those video's before Ron

    and I have seen EEVBLOG video's also on youtube

    Do you have any examples of when you use the ADD mode or Invert mode on the O-scope , for testing circuits or using it for troubleshooting?

    Do you have any examples of using the external trigger for testing circuits or using it for troubleshooting?

    I just need examples to learn from please

    Or you can makes them up and what comes to mind
     
  11. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    I think I can see the problem here, Unfortunately I think what you are after is a kind of, plug X board in and connect ext trigger to Y, twidle Z dial and the wave form will look like A/B.
    Billy trouble shooting isnt like that, People could give you 1000 examples of using the ext trigger, and not one example could fit anything you do. For example,
    Ok an example of using the ext trigger for trouble shooting. I have a LA (16500C HP) it is a real beast, it can do incredibly complex triggering, so say I have circuit and only on certain combinations of logic being on, it throws a glitch (maybe i2c comms or something), so I hook up the LA to all the logic inputs and outputs, I set the LA trigger to only trigger on a certain sequence, I connect the ext connection from back of LA to the ext scope connection, when the LA triggers so does the OS and I can see the waveform of the suspect part.
    Thats one example, but probably no good at all for you, and thats the point. Only you are there, no two situations are the same, you need someone there to go through YOUR kind of faults, troubleshooting is detective work, there is no book saying if you have this symptom then its always x y z at fault.
    You have to know and understand electronics first, only then can you look at a circuit and say, ah yes yes is meant to do this when that happens. Once you know how its meant to work you can workout whats wrong when it dosnt do it.
    Sometimes you get people that buy X box's etc on ebay because they have the three ring fault, they reflow the GPU and 9 times out of ten the fault is fixed. People (including themselves) think these people are clever because they can 'fix' something complex like a xbox. Its total rubbish, they are just copying a common workaround for a well known fault , far more clever is the person that first saw the problem, he probably knew a fair bit about electronics.
    Anyway point is, you cant jump to the trouble shooting pages until you read all the book, you need to learn electronics first Billy before you can go fixing these boards. Is a strange thing to be working at fault finding, without first knowing the basics.
     
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  12. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    More scope vids, the last one gives a good example of when and why to use a EXT trigger, again tho I cant see the application shown in the video being of use to you. But lets work on the assumption that all knowledge is good :D
    The scope in the last one looks same as my Lecroy! Really nice scope, almost as good as my beat up Gould


     
  13. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    OK, just off the cuff let's think back to something we discussed earlier. Remember when we looked at the vertical channel inputs and how on most scopes they share the same common? We also touched on special pre amp active probes that allow differential (rather than single ended) inputs? Using the Add Mode with an Invert function we can do a differential input trick using two channels. Take a look at the below circuit:

    Diff Inpt.png

    Keeping it simple here my voltage supplied to my divider consisting of R1 & R2 is 10 VDC. Now to measure a floating (off ground) voltage we can use the Add Mode and Invert one channel. As drawn Channel 1 is measuring V1+V2 relative to Common (Ground). Channel 2 is measuring V2 relative to Common (Ground). Now if I Invert Channel 2 I can negate the Channel 2 Voltage. Now I can Add the Channels together (algebraically) using the Add Mode. So now what I have here is really expressed as (V1 + V2) + (-V2) = V1. That would be 5 + 5 = 10 then 10 - 5 = 5. Now let's make R1 6.666 K Ohm and R2 3.333 K Ohm. Try working that out.

    Billy, this is just an example of using the Add mode with two channels and inverting one of the channels. This will always go back to what I have been stressing all along. Only once you gain an understanding of all of the features a scope offers will you know how to use and apply them as well as when to use and apply them. Keep in mind in my example I just used some DC levels. They could be other wave forms.

    As to an example of using External triggering if you still want one let me know. I thought we covered a few earlier in the thread?

    Ron
     
  14. Billy Mayo

    Billy Mayo Member

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    Yes just give me examples so I can learn from , or what you have done in the past on circuits or bench checked , etc.

    The Examples helps me learn how to use it , thanks

    I learned this trick in school, it's better to do differential AC voltages on an O-Scope cause a DVM meter can do the differential DC voltages

    Do you know any other tricks when the add mode or invert function? Why did they make the ADD and invert mode on the O-scope , what was it used for? I have not used it much in my experience only to do Differential AC voltages like your example

    Any other examples on using the ADD mode and invert function would help me out alot thanks
     
  15. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    The links I gave go into that, like I said before look at the guy's you tube channel, he goes into add and invert. Your getting lazy
     
  16. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    Billy, you may spend 40 plus years in electronics using a scope and never use some of the features. I gave you an example of using Add Mode with Invert of one channel. Again, knowing what the features and functions do is a big step in when to apply and use them.

    As to the External Trigger thing? Billy, I made an example using the circuit that you posted. It used your signals and everything. We can only beat this stuff o death so much.

    Here is your circuit:

    Comparator 1.png

    Here is what I modeled based on your circuit:

    Two Comparator Delay CKT.png
    ITwo Comparator Delay CKT.png

    I could Ext Trigger + Slope and about 0 Level on the output of U9. Using CH1 I could display the junction of C13 & R58 (the R*C timing network) while on CH2 I could display the output of U8. Note the points in time where the signals do things, like where the output of U8 goes positive with respect to the charge of C13.

    That was a model of pretty much your circuit. So there is your example again of triggering and using an EXT. trigger signal.

    That is about it for examples. You need to think of some and also take time with the scope and a small function generator.

    Ron
     
  17. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    Its all getting a bit repetitive ron, I also asked if he had access to a FG or some components like a 555 timer, resistors and caps, I just get ignored. Billy build a circuit with a 555 timer and probe about, in astable mode you should be able to get a good feel for scope coupling etc.
    Also build some filters and throw a swept signal through them, do you have a function generator with ext trigger and sweep?
    why does it feel like I am talking to a brick wall!:banghead:
     
  18. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    I agree LG, I just want to keep stressing (maybe pushing) the importance of lab exercises. Wish I knew what he had available to work with as to a signal source.

    Ron
     
  19. Billy Mayo

    Billy Mayo Member

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    Yes I learned that one

    I want others that are different, can you think of any those please?

    Circuits that you have tested or troubleshoot using the EXT. trigger?

    Like I used an Ext trigger for XXXX to troubleshoot this board or to test this board

    It's like If I was the Hiring person for a job interview and I asked you in your whole career what did you use the EXT. Trigger on the O-scope for and to do what, and you should say? list them please

    It's like If I was the Hiring person for a job interview and I asked you in your whole career what did you use the ADD MODE on the O-scope for and to do what, and you should say? list them please

    A lot of job interviews ask me this , so I need to know
     
  20. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    Have you considered the option of learning this stuff? then maybe you wouldn't need to go to so many interviews? If they ask you this sort of question, then I am guessing they are seeing if you actually know what its used for. It looks like you think you might be going for interviews soon?? is this by choice? or because they are starting to become unhappy with your performance?
    Just curious thats all
     
  21. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Why would they ask you that?
     

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