Posted by Texasmark1 on July 25, 2015 at 19:09:19 from (198.45.234.19):
In Reply to: Re: Burning points posted by Geo-TH,In on July 25, 2015 at 13:28:33:
"JohnT, How can anyone with today's cheap EVOMs measure resistance accurately, you can't zero them? Short the leads together and they always show a few ohms, not zero. I remember you could zero the old analog ohmmeters, but ohm scale was the least accurate of all the scales. As a student working at USNAD crane, I used to calibrate them. Not sure, been a long time ago, but weren't thay only 5% of the full scale reading? Or something like that.
You and Guido may have the last two with working simpson 260 in existence, well I'm sure some one else will tell me I'm wrong. BYW, wasn't Columbus the first to bring 260s to this country?
That said, why not just measure the primary current? Even my cheapo, FREE HF meters, are more accurate measuring current vs ohms. "
The currently popular digital multimeters like the HF yellow or red that cost $5 for most folks, do not zero like the old analog meters nor do they have 10k ohms/volt of source impedance. The lead resistance is like 4 tenths of an ohm. Big deal on anything but a ballast resistor on a tractor ignition system. But if you know what it is, it's still no big deal and you can read them down to 2 decimal places.....try that with a Simpson or Fluke......depends on which side of the meter your eyeball is located.....so they put a mirror behind the needle and turn it sideways to take out some of the guess work. Must have weighed 5 lbs too; the HF you don't even know it's in your tool bag. HF meters also have megohms worth of impedance in the front end so the meter doesn't load sensitive circuits like the volt-ohm Simpson or whatever and you don't wrap the needle around the stop peg if you screw up and select the wrong scale or wrong function. You don't have to find a Vacuum Tube Voltmeter to measure them...which does have a zero for the voltage.
Yeah times past were really great......right along with convergence circuits on color tvs and points and condensers for spark generating circuits, and coughing, raw gas belching Quadrajet carburetors and exhaust manifold heat risers that always stick closed and carbon steel exhaust systems, and body panels with no protection from salt and on and on. Yeah life was great back then.
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