[volt-nuts] Prema 6048 zero offset problems
David C. Partridge
david.partridge at perdrix.co.uk
Fri Jan 19 13:00:06 EST 2018
If there are any other members of the group with a 6048, I'd be grateful if you would attempt to recreate the scenario I describe to determine if this is just my meter or impacts other 6048 users.
Thanks
Dave
-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces at febo.com] On Behalf Of David C. Partridge
Sent: 18 January 2018 11:57
To: 'Discussion of precise voltage measurement'
Subject: [volt-nuts] Prema 6048 zero offset problems
Starting with a warmed up Prema 6048, if I power it off and then on, select 20V DC range, 4 second integration and connect to the 10V output of a Fluke 732A, I get a reading of:
+10.000047
If I reverse the polarity of the cables and allow the reading to settle down for a minute, I get a reading of:
-10.000006
If I short the inputs of the meter, I get a reading of:
+0.000105
which is different from the +0.000020 which I would have expected from the readings of the 732A output.
Proceeding on the assumption that the meter has stored a zero offset of -105uV
I then press the ZERO button to null out the offset and then reconnect the 732A in normal polarity I get an incorrect reading of:
+10.000153
This is not what I would expect to see - I would expect to see a reading of
+10.000047 - 0.000105 = +09.999942 This calculation
I then reverse the inputs and get a reading of:
-10.000113
which is close to the expected reading of -10.000006 - 0.000105 = -10.000111
I have mailed Prema about this problem, and will let you know what they have to say.
Cheers
David Partridge
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