[volt-nuts] Tilting LTZ1000A

Andreas Jahn Andreas_-_Jahn at t-online.de
Tue Nov 2 22:11:09 UTC 2010


Hello Frank,

here is my result from tilting the LTZ1000A in battery supply mode.
So connection is only at the output to a LT1043-based 2:1 voltage divider
and my 24-bit battery supplied LTC2400 based temperature compensated ADC.
Connection to the PC is via photocouplers. So the whole cirquit is floating.
To reduce drift of the ADC  I had to heat the ADC to about 28 degrees with
a temperature controlling cirquit.

Since a single ADC-measurement has about 10-20uVpp noise I averaged the
measurements within 1 minute (around 330 single measurements) to get the
noise to around 1uV referred to the ADC input. (giving 2uVpp referring to 
the LTZ).
For evaluation of the tilting effect I changed orientation every 10 minutes 
giving
5 minutes to settle the new value and averaged the last 5 minutes.
Resulting in about 1uVpp noise referred to the LTZ.

with the offset voltage of -0.01706 mV from the voltage divider the final 
results are:
Time  orientation verbal.     coded LTZ voltage  diff to zero diff (ppm)
15:20   0 degrees pins down     0 (7143.76684 mV) ( 1.60 uV) ( 0.22 ppm) 
(invalid)
15:30  90 degrees pin8 is up    1  7143.76468 mV   -0.56 uV   -0.08 ppm
15:40 180 degrees up side down  2  7143.76548 mV    0.24 uV    0.03 ppm
15:50 270 degrees pin4 is up    3  7143.76656 mV    1.32 uV    0.18 ppm
16:00 D-SUB up    pin6 is up    4  7143.76504 mV   -0.20 uV   -0.03 ppm
16:10 D-SUB down  pin2 is up    5  7143.76552 mV    0.28 uV    0.04 ppm
16:20   0 degrees pins down     0  7143.76524 mV    0.00 uV    0.00 ppm 
(zero)
16:30 D-SUB down  pin2 is up    5  7143.76548 mV    0.24 uV    0.03 ppm
16:40 D-SUB up    pin6 is up    4  7143.76400 mV   -1.24 uV   -0.17 ppm
16:50 270 degrees pin4 is up    3  7143.76580 mV    0.56 uV    0.08 ppm
17:00 180 degrees up side down  2  7143.76508 mV   -0.16 uV   -0.02 ppm
17:10  90 degrees pin8 is up    1  7143.76440 mV   -0.84 uV   -0.12 ppm
17:20   0 degrees pins down     0  7143.76516 mV   -0.08 uV   -0.01 ppm

The result at 15:20 is off against 16:20 and 17:20 so I decided to exclude 
it from the evaluation.
Since all values are near or well within my noise figure I cannot really 
tell wether
the values are real or simple accidently. But all changes are below 2uV or 
0.3ppm.



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