Playing around with an ammeter...

Discussion in 'After Hours Lounge (Off Topic)' started by Mike Lenthol, Oct 2, 2003.

  1. Mike Lenthol

    Mike Lenthol Second Unit

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    I just tried measuring different stuff around the house with a Fluke AC ammeter, and most devices were right on the spot. Microwave at 2Kw, incandescent light bulbs were showing within 1w of their rating. Even the 12v outside lighting system showed perfect reading. Pretty accurate throughout the range of the meter in other words.

    The 2 devices that showed strange results were an 19" LCD display and several fluorescent energy saving lights.

    The monitor is rated at 49w average consumptions, while the meter showed a consistent 240w! The fluorescent bulb rated 15w(60w incandescent light output equivalent) pulled 55w!

    Are these type of devices trick the meter by their nature of operation or were they falsely advertised?
     
  2. Holadem

    Holadem Lead Actor

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    You need to provide more details on your device. You said ammeter, but you're citing power and voltage. I will assume it's a multimeter. How do you get your measurements?

    --
    H
     
  3. Mike Lenthol

    Mike Lenthol Second Unit

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    It's a clamp on system. The clamp goes around just one of the AC wires and it displays the A(amps draw) value. I just take that and multiply by the line voltage, correct? Say a regular 100w incandescent bulb would show 0.8amps x 124v on the line = 99watts.

    The interesting thing is both device types showing incorrect readings are fluorescent. (LCD backlight)
     
  4. Dheiner

    Dheiner Gazoo

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    I think it has to do with the phase difference between the current and the voltage. It's called the power factor. Check here: Pf
     
  5. Mike Lenthol

    Mike Lenthol Second Unit

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    Yup that explains it. Found a good explanation about it in laments terms on google [​IMG] Btw, what power factor on average would a decent computer PSU have?
     
  6. Cary_H

    Cary_H Second Unit

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    Power factor isn't a big issue with single phase, household stuff. Efficiency of the device itself, or rather, how much power it wastes doing what it does, can count.
    I can tell you that I've seen 8 PCs and their CRT monitors, along with an assortment of incandescent and fluorescent lighting, all on one 120V circuit drawing 11ish amps.
    How are you taking these "out of whack" readings?
     
  7. Randall Duncan

    Randall Duncan Stunt Coordinator

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    Justin Lane Cinematographer

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