[volt-nuts] Fluke 5200A AC Calibrator

[David C. Partridge]

I just recently managed to buy a spares unit for my 5200A.

I'm delighted to report that between the two units, and after a bit of trouble de-soldering edge connectors, I now have a working, quiet (old fan was DEAFENING), but uncalibrated AC calibrator.

Checking the output is against my 7081, here is what I'm see on the 1V range set for 1V (the other ranges show a very similar pattern):

 Frequency  Reading    Error
 50Hz       1.00371    .371%  <--- Surprisingly high 
 100Hz      1.00091    .091%  <--- Surprisingly high 
 500Hz       .99993    .007%
 1kHz        .99990    .010%
 5kHz        .99991    .009%
 10kHz       .99991    .009%
 50kHz      1.00004    .004%
 100kHz     1.00003    .003%
 500kHz      .99718    .282%
 1MHz        .98859   1.140%	<--- This seems very high

Comparing the results against a 7150Plus which was connected in parallel, I get a different story:

 Frequency  Reading    Error
 50Hz        .99993    .007%  *** see below
 100Hz       .99989    .011% 
 500Hz       .99991    .009%
 1kHz        .99991    .009%
 5kHz        .99993    .007%
 10kHz       .99993    .007%
 50kHz      1.00028    .028%
 100kHz      .99933    .077%

Substituting a 7151 for the 7150Plus I get:

 Frequency  Reading    Error
 50Hz        .99986    .014%  *** see below
 100Hz       .99992    .008% 
 500Hz       .99997    .003%
 1kHz        .99997    .003%
 5kHz        .99997    .003%
 10kHz       .99995    .005%
 50kHz      1.00002    .002%
 100kHz      .99895    .105%


These figures are quite impressive for the 7150Plus and the 7151 as the 24 hour figures for the 7150Plus are 40Hz-10kHz range are .03% + 15 counts and the one year figures are .07% + 15 counts.  The 7151 figures are similar.

(***) I was only able to get a stable reading at 50Hz by grounding the low output of the calibrator.  I'm not quite sure what the problem is here.

If I believe the 7150Plus or the 7151, the calibrator is correct within the limits of the meters' accuracy.

If I believe the 7081, the calibrator is way off at the low end and high end of the frequency ranges.

Hmmmm ...

Does anyone have any suggestions as to why the 7081 seems to read so high at 50Hz, 100Hz and 1MHz, and whether the calibrator is wrong or the 7081?

Oh dear, life was so much simpler when I only had one clock!!!

Dave