Meter Good. Glasses bad? Didn't see the tiny decimal point in the
readout. Hell, this was the best $7 instrument the Chinese make. So,
divide readings by 10. My abacus doesn't even have a decimal point.
I have a more expensive Triplet needle type that is older than you are,
though. :-)
Don't think they even make the batteries anymore.
I do have a Professional Digital Model, but it is hidden away (lost in
the clutter) better than this one was, or it was "borrowed". Maybe I'll
find it, someday.
I am either going to have to spend more money, or be less trusting of
bargain sales. Maybe there is a $15 model from Malaysia? ;-)
Nice having you around to correct my errors. Thanks.
Steve
Theo Smit wrote:
> Hi Steve,
> Better get new batteries for that multimeter, or else use it as ballast.
>
> No selfrespecting digital multimeter would ever give a reading as high
> as 4 ohms with test leads shorted. I just repeated your tests on my
> test arrangement here, with these results:
>
> The setup is a Flamethrower II coil with a 0.05 ohm, 1% accuracy power
> resistor hooked up in series (that is so I can measure coil current
> with a live ignition system running, by recording the voltage across
> the resistor when the coil is charging, using an oscilloscope).
>
> Meter with test leads shorted: 0.3 ohms
> Meter connected across the 0.05 ohm resistor only: 0.3 ohms
> Meter connected across the coil only: 0.9 ohms
> Meter connected across a 1 ohm, 5% accuracy resistor (I use these in
> the tach modules): 1.2 ohms.
> Meter connected across two 1 ohm resistors in parallel: 0.7 ohms.
> Meter connected across three 1 ohm resistors in parallel: 0.5 ohms
>
> So here, if we subtract the 0.3 ohm "zero reading" from all these
> measurements, we end up with 0.6 ohms for the coil, 0.9 ohms for the
> single resistor, 0.4 for the pair in parallel, and 0.2 ohms for the
> three-resistor combination. If we assume a 0.1 ohm basic accuracy
> (since that is the smallest digit it will tell me), we can see that
> allowing for a 0.1 ohm offset, all the numbers come out pretty much
> exactly as expected for the known resistances, and the coil then
> measures at 0.6 ohms, plus or minus 0.1.
>
> Your resistance ratios may still be accurate, but the magnitudes are
> off by about one order, and that will also affect the theoretical
> power dissipated in the coil and/or resistor by a factor of 10.
>
> Theo
>
>
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Steve Laifman
Editor
http://www.TigersUnited.com
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