[volt-nuts] Traveling Standards - Measuring Protocol

[WarrenS]

A good thing to include in the "Measuring Protocol"
The type of filtering used  and a 24 hr plot would be a great thing to show.

In the LM399 data reported below, Its noise starts at 10-30 uv PP  (3 PPM)
Once per minute averaged readings gave 2 uv PP (0.3 PPM)
21 min moving average data is below 0.5 uv PP  (under 0.1 PP)
The PP variation over a couple hours time where the temperature is not 
changing is about 0.5 PPM

What I've seen is that the LM399 has good TC over a wide temperature but 
they
can be pretty noisy PP short and medium term when measured at the sub PPM 
level.

The total PP noise on the plot I posted of the selected 1N825#2, running at 
its 'Zero-TC' current
shows about 0.1 PPM variation over the couple hours where the temperature is 
not changing.
The plot is once per second samples taken from with a 15 sec analog RC 
filter time constant.
http://www.febo.com/pipermail/volt-nuts/attachments/20110904/15d2a3ab/attachment-0001.jpg

All 1N825 are not the same. Starting with a selected low noise one,
it must then be aged and run in at 50 ma for a long time before it is fully 
stabilize.

ws

***********************
> From: "Andreas Jahn" <Andreas_-_Jahn at t-online.de>
> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
>
>Hello,
>
>the red curve is one measurement with an integration time of 1 minute.
>(about 350 measurement values of LTC2400 ADC with 10-30uVpp
>noise averaged giving around 2 uVpp for 1 minute integration time).
>
>the light blue trace is the sliding average over 21 minutes of
>the red curve.10 minutes before, current minute and 10 minutes after.
>(so noise is reduced down to below 0.5uVpp).
>
>Total measuremen time (x-Axis) is around 940 minutes.
>
>with best regards
>Andreas