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Analog Meter

Discussion in 'General Electronics Chat' started by windozeuser, Sep 7, 2005.

  1. kiriakos-gr

    kiriakos-gr Member

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    I agree too, but I had find out about it , almost by luck ..
    So I am very forgiven on the others, who does not know an such detail.

    In my case , I got the portable calibrator pictured above.. and in the specs it says that at 10mA setting it can be used so to supply an adjustable 0-8V DC ...

    I tested this with my latest and greatest True RMS Fluke 87-5 ,
    and I got nothing as adjustable .. other than an full voltage reading of 8,4V .

    As soon I connect on it my, analog one ... It started to work ..adjusted output and all.

    By the way, how long are your leg ? :D

    Nice meeting you man ... My journey over the WWW serves only one purpose,
    to find and other people, who they know of what they talk about,
    and you are one of them .. ;)
     
    Last edited: Aug 11, 2010
  2. The Electrician

    The Electrician Active Member

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    Maybe you should explain what you mean when you say "load" a forward biased junction. What an analog ohmmeter does is pass a current through the junction, and that's the same thing a DMM does.

    Furthermore, when using a DMM to test a junction, one shouldn't just rely on a "beep". The meter will indicate the forward bias voltage across the junction when it carries the milliamps current put out by the DMM. That voltage varies with the condition of the diode--shorted, open, damaged or in good condition; for example, you can tell the difference between a Schottky and a non-Schottky easily.

    You say there's "Absolutely nothing in between"; this is not true. The forward voltage of the diode is shown by the DMM, and this is same information you get with the ohms function of an analog meter. The analog ohms range just doesn't indicate the forward voltage directly, but you can learn, as you obviously have, to interpret the ohms reading. A DMM's reading of the forward voltage gives the same information. The ohms reading on an analog meter doesn't tell you any more than knowing the forward voltage does; it's telling you the same thing in a different format.

    DMMs don't "lie" either; they tell you what the voltage across a junction is when it's forward biased with a few milliamps. You don't just rely on "beeps; you look at the value of the forward voltage. It's not just a matter of a beep or no beep. It's not true that there's "Absolutely nothing in between." There's a forward voltage reading. This reading gives the same information as the reading on the ohms scale of an analog meter. It tells you the voltage drop across the forward biased diode, which is the same information an ohmmeter gives you. The ohmmeter converts it to an ohms reading, but it's the same information.

    One can just as easily "learn to know" the DMM with "readings on good junctions that are forward biased" by the DMM.
     
    Last edited: Aug 11, 2010
  3. kiriakos-gr

    kiriakos-gr Member

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    Issues like those will puzzle us for years , like theory VS praxis.

    For instance, some one , could find that one small relay has burned contacts,
    by the sound of an non latched beeper. (cheap DMM )

    The lathed beeper ... will beep , but the quality of the contact its not traceable by it !!
    (expensive DMM )
     
    Last edited: Aug 11, 2010
  4. dave

    Dave New Member

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  5. tvtech

    tvtech Well-Known Member Most Helpful Member

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    I am working on it. Waiting for a Telefunken TTV 74 CM to come in again that is dead. Chopper transistor is good, mains fuse is good, all is good on the Primary side. Just dead as a doornail.

    No Secondary shorts dragging the PSU down. Line stage is disconnected.

    And yes, the two 120K startup resistors are both fine on the Primary......

    The answer lies with the 2SA1015 that is coupled to the Opto-Coupler on the Primary. One of the junctions breaks down UNDER LOAD. Reads OK on Digital. Reads crappy on an Analogue.........I have seen Techs literally pull their hair out over this fault using Digital Meters. I come along with my old fashioned Analogue and nailed it. And there are many more examples. But to prove a point, I will post back here with photo's etc of what the Digital says vs the Analogue with the faulty transistor. Should be in this week...we get loads of them in that "mechanics" cannot fix.

    Another thing I may as well say. I am not posting this to try and look smart. I am pretty comfortable with my TV repair skills. They have served me well for a long time.

    Just sharing what always works for me :)

    And that is what Forums are for. I think.

    Cheers
     
    Last edited: Aug 14, 2010
  6. kiriakos-gr

    kiriakos-gr Member

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    Do not deny your Carma ... electronics are the arena for the smart and trained people.

    The ones who had designed them ( electronics circuitry ) had the ultimated education , and this people was not stupid too.

    One medium educated person , it must to be smart,
    so have ability to cover the missing " education " gap .

    Or else , he will be unable to diagnose and repair .
     
    Last edited: Aug 15, 2010
  7. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    I believe if we wander back to the beginning of this thread we will find some very good answers to the pros and cons of each type of meter. Even today, they each hold a place in diagnostics and trouble shooting techniques.

    Those of us who grew up in the era of analog meters may tend to gravitate to them as a useful tool even today. That does not make the analog VOM a better meter. It did take more understanding to read the scales on an analog meter. However, let's face it in that a DMM does offer greater accuracy and resolution (resolution being the ability to read the instrument or of the instrument to be read).

    kiriakos-gr makes a good point in mentioning "Or else , he will be unable to diagnose and repair" in that the use of a meter is generally for fault diagnosis or repair. This is where the end user needs to know the best tool to do the job. To many, the analog meters pictured in this thread represent old junk while to some of us they represent a valuable tool in diagnosing a fault. Pretty simple really.

    In conclusion I figure (and just my opinion) that a well armed tool box should contain both meters. Additionally a well versed user to know which tool to use for which job.

    Ron
     
    Last edited: Aug 15, 2010
  8. kiriakos-gr

    kiriakos-gr Member

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    By making my own resistors decade, ( not completely finished yet ),
    I started testing it with my analog meter ...

    Its spot on !!

    So I will say that the auto-range its the only benefit as function , to any multimeter ..

    And lets not exclude the factor "price tag" .
    There was always premium quality meters , and average ones.
    The premium ones , was and are, for the few ..

    Thats why, is very hard to offer one conclusion that will properly categorize,
    performance - usability - needs.

    The sad part are that this days there are very few high quality analog meters.
    Thats why I had to search , for something made in the far past,

    I do not know maybe its just me .... I have start to love this black brick .. :)
    ( I get in love quick, with anything that smells perfection )
     
    Last edited: Aug 15, 2010
  9. tvtech

    tvtech Well-Known Member Most Helpful Member

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    Just for interest sake....did a test on a good BD243C today.

    Checking forward bias current Base Emitter and Base Collector using a YEW, a cheap 20K/V Analogue and a Fluke.
    The Analogue meters set on X1 and the Fluke on "beep" for good or bad junctions.

    The YEW put 73mA through each junction as tested forward biased one at a time. The cheap 20K/V Analogue put a little more @ around 106mA per junction .

    The Fluke managed to push only around 0.4mA per junction with the same Transistor.

    That's what I am talking about. A little "loading" goes a long way to checking a Forward biased junction for possible failure/problems.

    Check it out yourself...you might learn something. And this is a Transistor with perfectly working junctions. A Transistor/junction that is failing reveals itself quickly on an Analogue not on a DMM. And yes, I am not talking about leaky junctions. A Fluke will pick that up. I am talking about junctions that show no leaks when reverse biased but have Forward bias problems.

    Thank you
     
  10. The Electrician

    The Electrician Active Member

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    Does your Fluke only "beep", or not "beep" when using the diode test function? Doesn't it show some numbers in the display?

    You still haven't told us what you mean by "loading", so I have to guess. It appears that you mean that some current is passed through the diode in the forward direction; is that correct?

    What model is your Fluke? What does it indicate if you use the Fluke on ohms range, instead of diode test range?

    Do you have a known bad diode from a repair job lying around? What does your analog meter show on X1 ohms range when testing the bad diode in the forward direction? What does a good diode of the same type indicate on the X1 ohms range of your analog meter?

    Now, measure that same bad diode and good diode on the ohms range of your Fluke DMM; do you get different readings?
     
  11. tvtech

    tvtech Well-Known Member Most Helpful Member

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    Very old thread here...but nevertheless...

    Lately, Frame IC's that "appear to have failed". Problem is the 1N4001 supplying the Frame IC stops conducting and simply goes open......A YEW reveals it.

    A Digital Meter does not. My "Technician" was replacing and repeatedly changing the Frame IC....like normal. Spares wasted. Till I showed him :)

    Now, he is clever again. Until the next time. Now every TV with a Frame problem....Automatically...the Diode is changed. Faulty or not.

    LOL :D
     
    Last edited: Sep 28, 2013
  12. The Electrician

    The Electrician Active Member

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    You say the diode goes open. If it's open, there is no question of whether it shows damage if the forward biased direction--it's simply open; no conduction in either direction. If your digital meter can show any indication at all of a 1N4001 that is good (in the forward bias direction), then it can distinguish between a 1N4001 that is open and one that is not.

    Does your digital meter show any indication at all with a known good 1N4001? If it does, then it can reveal an open 1N4001. If it doesn't, then get a better digital meter.
     
  13. tvtech

    tvtech Well-Known Member Most Helpful Member

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    You are talking in riddles.

    Regards,
    tvtech
     
  14. The Electrician

    The Electrician Active Member

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    Not at all. Are you afraid to answer my questions?

    I asked you a number of questions 3 years ago which you never answered. Why not? They are not riddles; they can easily be answered. I'll ask again, along with this new question: does your digital meter give any indication at all with a known good 1N4001, connected in either direction?

    The old questions:

    What model is your Fluke? What does it indicate if you use the Fluke on ohms range, instead of diode test range?

    Do you have a known bad diode from a repair job lying around? What does your analog meter show on X1 ohms range when testing the bad diode in the forward direction? What does a good diode of the same type indicate on the X1 ohms range of your analog meter?

    Now, measure that same bad diode and good diode on the ohms range of your Fluke DMM; do you get different readings?
     
  15. tvtech

    tvtech Well-Known Member Most Helpful Member

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    The Electrician

    Regarding your post above I believe I explained all questions in your post above three years ago. I use my Fluke 75 for new projects. I use my YEW for repair work. You will not find my Fluke on my repair bench.

    The concept of "loading" a Semiconductor junction is not new to practicing techs that know their game.

    The 1N4001 diodes mentioned above read fine with any Digital Meter. Never mind a Fluke. Forward bias is correct and no leakage reversed biased.....

    The problem that an analogue meter picks up that a digital does not is that it loads the junction under test. And the junction shows up faulty with an Analogue Meter.

    I am not prepared to argue with you. I tossed Digital Meters years ago with repairs (covered in this thread)

    I think I have maybe 20 or more faulty components that I specifically saved for a situation like this...when I have to prove to people..

    Why should I bother though???. You like Digital for repairs......go for it and eventually find out the hard way. Not my time you are wasting :p

    Best regards,
    tvtech







     
  16. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    While I think tvtech is rather overstating the difference, I fully agree that analogue meters are FAR better for testing semiconductor junctions (and old Avometers particularly), simply because they put a reasonable amount of current through the junction.

    However, he seems a bit 'confused' about his frame problems? :D

    The 1N4001 isn't 'feeding the frame', it's the bootstrap diode (a 1N4001 isn't fast enough to be the rectifier feeding the frame from the LOPT), and I can't envisage any reason for testing it on ohms?, you would simply measure the voltage either side of it (or check with a scope).
     
  17. tvtech

    tvtech Well-Known Member Most Helpful Member

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    Hi Nigel

    All you say is true. I know it's the bootstrap diode and it does not "feed" the Frame Stage....other than that I was trying to get a simple message through to people about testing components with a DMM versus an Analogue Meter. My Frame Stage is not confused :p. I have the full picture here.

    Stay well and thanks for chirping :)

    All the best,
    tvtech
     
  18. WTP Pepper

    WTP Pepper Active Member

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    There are so many pro's & cons of both. The problem I find day to day is that most engineers have no idea how to interpret what they are seeing from either type of meter.
    e.g. Measuring the idle current of a CPU circuit (uA) then trying to measure it's current when it starts up (~20mA). The CPU always resets. Go figure.
     
  19. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    i have been given several very old AVO meters! they are ace i have got 3 working and have 3 to get working. nothing beats watching the needle move and the feel of the knobs. my bench DMM is way way more accurate but not as much fun
     
  20. The Electrician

    The Electrician Active Member

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    I asked a number of questions in post #49. You never responded to them. How can you say that you "...explained all questions in your post above three years ago."? How does not responding constitute explaining all questions?

    Which 1N4001 diodes are you referring to? The ones you described in post #50? If those are the ones you mean, you said they were "open". When diodes are "open", they don't conduct at all in either direction; how then can they read fine with any Digital Meter, or give any indication at all with any meter?

    In post #50 you said:

    If the 1N4001 is "open", then no meter, analog or digital will "read fine" on that diode. Yet you say "A YEW reveals it. A Digital Meter does not." If the diode is "open", the YEW would reveal it by giving no reading at all. A digital meter would do the same thing; no reading at all.

    Maybe you mean something different by "open" than I do. So, please explain how the YEW reveals an "open" diode. What indication does it give?
     
  21. throbscottle

    throbscottle Well-Known Member

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    Many older service manuals specify voltages as measured with a meter resistance of "20,000 ohms per volt" - standard with many analogue meters such as the AVO 8. Digital meters make these voltages look higher than the manual states. Personally I have a Mastech combined "digit and pointer" meter - shows up rapid changes whilst having the easy to read digital scale.
     
  22. throbscottle

    throbscottle Well-Known Member

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    Many older service manuals specify voltages as measured with a meter resistance of "20,000 ohms per volt" - standard with many analogue meters such as the AVO 8. Digital meters make these voltages look higher than the manual states. Personally I have a Mastech combined "digit and pointer" meter - shows up rapid changes whilst having the easy to read digital scale.

    Ok managed to post reply twice... not clever. Also posted before reading pages 2 and 3, and not seeing how old this thread is! Ho hum...
     
    Last edited: Oct 1, 2013

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