• #### Error of % + digits?

From Commander Kinsey@21:1/5 to All on Thu Jun 18 14:03:42 2020
XPost: sci.electronics.basics

I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean?

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• From Commander Kinsey@21:1/5 to Commander Kinsey on Thu Jun 18 14:28:10 2020
XPost: sci.electronics.basics

On Thu, 18 Jun 2020 14:03:42 +0100, Commander Kinsey <CFKinsey@military.org.jp> wrote:

I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean?

Answering my own question, I found this page, it means aswell as the percentage error, the last digit (eg the 2 in 147.2V) can vary by 3.:

https://www.baylor.edu/content/services/document.php/49697.pdf

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• From Michael Terrell@21:1/5 to All on Thu Jul 16 10:54:08 2020
208 is a standard three phase voltage. It is three 120 volt lines phased 120 degrees apart.

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• From Michael Terrell@21:1/5 to All on Thu Jul 16 13:13:11 2020
He is just an arc flash away from making an ash of himself.

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• From Commander Kinsey@21:1/5 to Michael Terrell on Fri Jul 17 00:02:03 2020
On Thu, 16 Jul 2020 21:13:11 +0100, Michael Terrell <terrell.michael.a@gmail.com> wrote:

He is just an arc flash away from making an ash of himself.

I've done that actually, just scorched my hand for a couple of weeks.

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• From Commander Kinsey@21:1/5 to Michael Terrell on Fri Jul 17 00:15:25 2020
On Thu, 16 Jul 2020 18:54:08 +0100, Michael Terrell <terrell.michael.a@gmail.com> wrote:

208 is a standard three phase voltage. It is three 120 volt lines phased 120 degrees apart.

Ah, I didn't know that existed. I thought you only got 120 when you centre tapped a single 240. If you're gonna use three phase, wouldn't you want more voltage?

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• From Ralph Mowery@21:1/5 to All on Thu Jul 16 23:29:38 2020
In article <op.0nvd9pimwdg98l@glass>, CFKinsey@military.org.jp says...

He is just an arc flash away from making an ash of himself.

I've done that actually, just scorched my hand for a couple of weeks.

If you had respected things that probably would never hapen, you would

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• From Commander Kinsey@21:1/5 to Ralph Mowery on Fri Jul 24 22:09:31 2020
On Fri, 17 Jul 2020 04:29:38 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote:

In article <op.0nvd9pimwdg98l@glass>, CFKinsey@military.org.jp says...

He is just an arc flash away from making an ash of himself.

I've done that actually, just scorched my hand for a couple of weeks.

If you had respected things that probably would never hapen, you would

You miss the point, it's not the end of the world.

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• From Rich@21:1/5 to Commander Kinsey on Fri Jul 24 22:58:41 2020
Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 17 Jul 2020 04:29:38 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote:

In article <op.0nvd9pimwdg98l@glass>, CFKinsey@military.org.jp says...

He is just an arc flash away from making an ash of himself.

I've done that actually, just scorched my hand for a couple of weeks.

If you had respected things that probably would never hapen, you would

You miss the point, it's not the end of the world.

A scorched hand, no, not the end of the world.

A stopped heart, which *can* happen if the arc flash conducts enough
current through the wrong part of the body, well then for the one who's
heart just got stopped it might just be the end of the world.

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• From Commander Kinsey@21:1/5 to Rich on Sat Jul 25 00:31:03 2020
On Fri, 24 Jul 2020 23:58:41 +0100, Rich <rich@example.invalid> wrote:

Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Fri, 17 Jul 2020 04:29:38 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote:

In article <op.0nvd9pimwdg98l@glass>, CFKinsey@military.org.jp says...

He is just an arc flash away from making an ash of himself.

I've done that actually, just scorched my hand for a couple of weeks.

If you had respected things that probably would never hapen, you would

You miss the point, it's not the end of the world.

A scorched hand, no, not the end of the world.

A stopped heart, which *can* happen if the arc flash conducts enough
current through the wrong part of the body, well then for the one who's
heart just got stopped it might just be the end of the world.

It seldom travels that path.

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• From Cydrome Leader@21:1/5 to Commander Kinsey on Sun Jul 26 03:53:08 2020
XPost: sci.electronics.basics

In sci.electronics.basics Commander Kinsey <CFKinsey@military.org.jp> wrote:
On Thu, 02 Jul 2020 06:45:42 +0100, Cydrome Leader <presence@mungepanix.com> wrote:

In sci.electronics.equipment Ralph Mowery <rmowery28146@earthlink.net> wrote:
says...

So should I assume the cheaper ones are lying? Or have they just made a rough estimate adding the two errors?

might be both. I dug out my first DMM, a Wavetek DM2, circa 1990s. It might
have been from a raffle or something like that.

The DC voltage specs range from 0.8% +1 digit (not bad really) over to the
AC ranges which are "1.2% RDG +10 Digits". If I had new leads, I'd trust it
with outlet voltage, but would stay away from 208volts. The meter has 3.5 >>>> digits or max display of 1999. I'm figuring a real 100volt AC reading could
be 99 to 101 plus another error of +/- 1 volt for the 10 digits tolerance >>>> on the display or count. so 100volts from your Japanese outlet reference >>>> might read 98 to 102 volts. So while in the ballpark, it's better than you >>>> can read off a Simpson 260 meter in the AC voltage range. I could be wrong >>>> on this too.

It's a pretty decent meter for poking at DC circuits for the tens of
dollars is must have cost when new.

It seems that maybe due to modern manufactoring the meters are more
accurate than they were 20 years ago. I bought some DC voltmeters from
China. They display 3 digits. They read from 0 to 99.9 volts. I coulg >>> get 4 of them for less than \$ 15 including the shipping. I hooked all 4 >>> of them in parallel with a Fluke 87 . Three of them tracked right along >>> with the Fluke with the last digit sometimes being one high or low from
0 to 24 volts. The fourth one was off by an average of 2 on the last
digit. I found an adjustment screw on the back of the meter and tweaked >>> it and re ran the test. It then fell in line with the other meters.

Have you run this test with AC? That seems to be where the wheels come
off. I brought up this thread to a friend and he mentioned his quest to
repair some sort of HP true RMS meter that uses a thermocouple and heater
to properly measure complex waveforms. I can't even guess how slow such a
meter might be.

How well do these things work measuring dodgy waves like from a cheap UPS or invertor?

Probably perfectly.

I had 3 or 4 of the Harbor Freight 'free' multimeters. The ones that
usually sell for around \$ 5. They seem to be reasonable accurate for
the money. Plenty accurate for the home user to test things around the
house. I do admit that the safety issue of putting them across the 120
or 240 volt power wires is somewhat doubtful. I sure would not use one
where I worked to put across the 480 volt 3 phase system that is fused
with 200 amps.

I'm pretty timid with anything upstream from a plain outlet.

I've replaced outlets (240V, not the namby pamby USA stuff) without
turning off the power - other outlets on the same circuit were being
used in the office and I saw no point in interrupting them.

cool story.

Just keep your fingers off the metal things and don't short stuff together. Wear goggles and gloves if you want to be a girl about it.

edison base fuse burst in my hand once. Never seen one come apart before.
It was just a 120v lighting circuit, but right off the service panel.
There's way more excitement near those things.

Try shorting two phases together with 500A cables. That causes lots of smoke, a fire alarm, 3 fire engines, and a visit from the power company.
Do not ever employ Irish electricians.

In America we have fuses and circuit breakers. Check youtube for a video