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
Result of nonlinearity and dc offset combined?
Bruce
On 19 January 2018 at 00:57 "David C. Partridge" <david.partridge@perdrix.co.uk> wrote:
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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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@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
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.