On 12/09/2014 08:36, John Phillips wrote:
From what I remember: The 3455A has a good AC front end but is a real pain
to calibrate with a lot of adjustment (read flexibility). I think HP gave
up a lot of accuracy for a simpler calibration. The 3457A seems to do AC a
lot better than the 3456A. Nether meter come close to doing what the 3458A
does.
On Fri, Sep 12, 2014 at 12:04 AM, M K <[email protected]> wrote:
On 12/09/2014 00:30, Richard Moore wrote:
I'm trying to get my head around the AC cal procedure for the HP 3456A --
there is no full-scale cal, just some extremely finicky tweaks for the
bottom ends of three of the four ranges. I really don't understand how this
is supposed to work, especially since it is very accurate on all DC ranges
(up to 500V -- above that some heating of the divider R seems to occur and
it loses accuracy as the voltage increases). But on AC, the tweaks don't
result in anything like an accurate level reading compare to my 3458A -- at
10VAC it is off by hundreds of ppm. Anybody shed any light on this? Is
there a way to get full scale cal points in AC mode? Any mods to fix this
-- lovely meter otherwise; I much prefer it to the 34401A I used to have,
except for the overall bigness....
Hi Richard,
Does the meter have a DC to RMS converter chip in it, because if it does
you have to account for the self noise and offset of the gilbert cell at
the heart of the converter.
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I downloaded the service maual from the BAMA archive, it is an absolute
value circuit followed by a logging anp, not quite the AD634 gilbert
cell, but still prone to the same offset and noise creating a
non-linearity at the bottom of each range.
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