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Thread: AlanB's Drop In Dream Come True - Regulated Driver!!

  1. #31
    *Flashaholic* wquiles's Avatar
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    Default Re: AlanB's Drop In Dream Come True - Regulated Driver!!

    Right now your Fluke is setup for plain vanilla DC voltage measurement, which can't possibly account for the PWM signal's duty cycle.


    You need to set the Fluke 187 to the special DC mode in which the display will show "AC + DC". To get into that mode, press the small blue button on the right side a couple of times, until the display shows "AC+DC". Then the Fluke will display the proper value, which will be around 17.5V.

    Will
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  2. #32
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    Default Re: AlanB's Drop In Dream Come True - Regulated Driver!!

    Thanks Will! I got this meter used, never really learn how to use it.

  3. #33
    Flashaholic* Alan B's Avatar
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    Default Re: AlanB's Drop In Dream Come True - Regulated Driver!!

    Quote Originally Posted by wquiles View Post
    Right now your Fluke is setup for plain vanilla DC voltage measurement, which can't possibly account for the PWM signal's duty cycle.


    You need to set the Fluke 187 to the special DC mode in which the display will show "AC + DC". To get into that mode, press the small blue button on the right side a couple of times, until the display shows "AC+DC". Then the Fluke will display the proper value, which will be around 17.5V.

    Will
    Good catch, Will.

  4. #34
    *Flashaholic* wquiles's Avatar
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    Default Re: AlanB's Drop In Dream Come True - Regulated Driver!!

    Quote Originally Posted by Alan B View Post
    Good catch, Will.
    No problem. Just trying to help

    Will
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  5. #35
    *Flashaholic* LuxLuthor's Avatar
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    Default Re: AlanB's Drop In Dream Come True - Regulated Driver!!

    Quote Originally Posted by wquiles View Post
    From what I have read, and from my own bench experience with various Fluke's with and without the AC+DC mode, you can't really correlate very well the Fluke 179 and the Fluke 189 when measuring the PWD signal due to the varying duty cycle. How well it would correlate would depend on how close to a 50% duty cycle the PhD regulator would be running during your measurements. The RMS function on a "normal" True RMS Meter applies to a duty cycle around 50%, which is the narrow range in which the 179 would measure reasonably close. I experienced this on my Fluke 87 almost 3 years ago when testing the PWD driver from Willie Hunt, and being frustrated about the lack of "accuracy". You can see in this post how I am using the RMS equations to turn the non AC-DC measurements into the approx. value of the true RMS voltage:
    http://www.candlepowerforums.com/vb/...ighlight=Fluke

    Once you depart from the 50% duty cycle (towards 0 or towards 100), then only meters with the AC+DC will be able to measure accurately, although once you get in the duty cycle in the 0-5%, not even the 189 measured correctly: I seem to remember it was something to do with the crest factor exceeding 6, or something like that. I "captured" this problem with the 189 last year in Alan's original collaboration thread, including this older post, where the lowest level was not even close, the next level up was close, and then on it was accurately giving me the expected voltage:
    http://www.candlepowerforums.com/vb/...1&postcount=15

    Will
    Love all the great feedback.

  6. #36
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    Default Re: AlanB's Drop In Dream Come True - Regulated Driver!!

    How are the newly arrived regulators going - what setups are you using them with?
    So many lights, so little money (cause I spent it on lights). I'm not afraid of the dark, the dark is afraid of ME!

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