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...
On Tue, 7 Apr 2015 07:30:13 -0400, "Jim Wilkins"
wrote:

wrote in message
. ..
On Mon, 6 Apr 2015 21:55:09 -0400, "Jim Wilkins"
wrote:


The cheap ones are far from accurate. I bought 2 on ebay - both
were
in-accurate, and they didn't even match each other. (readings
were
different and didn't match my 3 multitesters, that all agreed
within
less than 1/10 volt and less than 1/100 amp

Look closely, mine had tiny calibration trim pots.


These useless pieces of scrap didn't.

They look like flathead mounting screws rather than pots. This one
is
2mm in diameter.

-jsw

I know whst they look like - and they are not there. It uses "laser
trimmed resistors" for calibration - and I think they over-trimmed
them. Suspect what is sold on e-bay direct out of china is the
rejects
for some brand name product sold elsewhere at significantly higher
price

I've been satisfied with this USB power meter:
http://www.amazon.com/gp/product/B00...d_i=B00HTAH3KY

I don't remember exactly how accurate it was, and another could be
different. It was close enough to tell which USB hard drives would run
comfortably off the laptop USB2 port (WD) and which were marginal
(Seagate) and should be on USB3 or a powered hub.

I sorta wish I'd bought a dual display meter because the drives can
take longer than the Volts / Amps display switching interval to come
up and stabilize.

-jsw