"Clare Snyder" wrote in message
...
On Thu, 8 Mar 2018 07:09:40 -0800 (PST), "Dave, I can't do that"
wrote:

Thanks guys, I have just decided to stay with the single wire. I was
being lazy as it is a bit of a struggle to get enough room for the
clamp between them.

This morning it (correctly) measured the 11A and 9A but the combined
was 19A, so obviously it is confusing the meter with a variety of
probable causes as was mentioned in your replies.

I will just stop the laziness and use the single wire from the
junction block to the control board. That is always accurate when
checked with the pass-through meter. It just confused me a little as
I was pretty sure 11+9 did not equal 14 and then this morning with
the meter quite cold, it showed 19. That could have easily been
confused as 11+9 is close enough to be 19 and thus assumed that
measuring both was near-enough. That could have been nasty.

When combined it probably has something to do with the temps (19C at
the moment) as was also mentioned. The single wire clamp and
pass-through readings seem accurate despite the temp. It was about
25C yesterday when I got the 14A double-wire reading.

Lesson learned and thanks anyway.
Perhaps a "rounding error"? If the 11 was really 10.6 and the 9 was
realy 8.6, the REAL current would be 19.2, and the combined reading
would round to 19

If the measurement circuit could resolve to tenths the maker would add
another digit to the display, and to the price.

http://en-us.fluke.com/training/trai...precision.html

The standard assumption is that the displayed reading can be off by at
least 1 count. "11" could be 10 or 12, "9" could be 8 or 10, so the
sum could be from 18 to 22. Notice that the sum of two 10% errors is
still a 10% error.

-jsw