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  • 1 Post By Stoney

Thread: pwm errors

  1. #1
    Senior Member
    Join Date
    May 2010
    Clagiraba, Queensland

    pwm errors

    i just stuck this up on UKV .. proud if it, kets see if a copy works with tapatalk..

    sigh .. a normal voltmeter does NOT give an rms, or correct answer unless its a DC only device or an exxy true rms meter.
    thats it, no ifs or buts .. wrong.
    at high dutys, single batterys, the error is not huge though and simply makes NO difference in vaping terms.

    heres a couple of graphs .. I can show the error between rms and average volts is 1/root(duty)

    so this graph is a plot of duty cycle (bottom axis) vs error to rms volts (left axis)

    highlighted point is vmax on minimum duty roughly 36% .. rms is 1.6 times higher, 3v is really 4.8v
    an ego is waaay over on the right, 0.9 duty .. 1.05 rms, 5% error

    but .. you square it to find power ..
    this is duty cycle .. bottom axis, vs error in power if you measure the voltage with a meter and use that to calculate your power.

    again, highlighted spot ... vmax on min, the power is 2.7 times what you calculate..
    again.. ego .. waaaay over on the right at 0.9 .. error about 10% now. big deal.

    so I state again .. it makes bugger all difference on single battery mods, HUGE difference on dual batt mods particularly at low voltages.
    Fatman likes this.
    In order of useful: Provari V2 and V1, vamo, eGo twist, Katana v3, Hex, Orion v2, LavaTube, eGo x 6, VMAX, 510N, Tick V2, Tick V1, noEgo 18650, noEgo 14650 , Indulgence x 2, 905 6v mod, KR808D

  2. #2
    AVF Regular
    Join Date
    Jul 2012
    Sydney NSW
    Very handy graph mate.
    Great Stuff!
    Shop at Supersports600 eBay Store for all your Battery and Nicotine testing needs



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