[volt-nuts] Zener selection: was Traveling Standards - Measuring Protocol

[Andreas Jahn]

Hello Warren,

to come back to your zener diode selections:

- do you have any source where the selection of zener diodes is described?
I have read on a german page that zeners are selected by
their "noise characteristic". And that the noise will show the long term 
behaviour.
But its not described which kind of noise has an influence.
Is it broad-band noise? 0.1 to 10 Hz noise? or even the lower frequency
noise (which you have recorded on the strip chart recorder).

>From the german link it is not clear wether the selection is
according to the value of the noise or the change before
and after pre-ageing.

And the bad news is that my LM399#1 which is drifting
much more than my LM399#2 has only about 50% of
0.1 to 10 Hz noise than the LM399#2.

By the way how do you make the plots?
Do you always record the difference of two similar devices to
compensate for the DC-Offset?
Has the strip chart recorder 1uV resolution or do you have
to add a pre-amplifier? (which one?).
The 10 second time constant: is it built in within the recorder
or external (low-ohmic / high ohmic resistor + what kind of capacitor)

with best regards

Andreas

----- Original Message ----- 
From: "WarrenS" <warrensjmail-one at yahoo.com>
To: <volt-nuts at febo.com>
Sent: Wednesday, September 07, 2011 6:36 PM
Subject: Re: [volt-nuts] Traveling Standards - Measuring Protocol


> Bob
>
> First I'd like to say that what your doing is a great idea and could be a
> great benefit to the Volt nut group.
> Now for some comments that I hope you will find useful to get the most 
> from
> this exercise.
>
> I'm still hoping you will post more details and if need be get suggestions
> for the measurement that YOU should make before sending the TS out.
>
> When doing short term stability testing better to do it at a Higher
> resolution than 1.7 PPM / count.
> One way to do that is to put your 6 digit voltmeter on the 1V or better 
> yet,
> the 0.1V range and measure the difference between the Device you're 
> testing
> and
> a similar stable non-effected voltage such as a second device of the same
> type that is not being subject to the things you're testing for.
> Then taking into consideration that noise measurements are the RMS sum of
> the two devices and Drift measurements are the Difference between devices,
> it is possible to greatly increase the accuracy of the measurements.
>
> Also very useful to measure the actual Temperature Coefficient of the
> devices so that the temperature readings have more meaning.
>
> When evaluation precision voltage references,
> I find it very helpful to make a High Resolution strip chart recording, be
> it Analog or Digital,
> Preferable showing Both temperature and voltage.
> For an example of how I get much better than 0.1 PPM resolution using 50
> year old technology,
> See attached plot comparing two 10 volt devices, using a slow, dual 
> channel
> analog Rustrak recorder and Fluke 845A/B null meter
>
> Just my two cents worth to the bigger picture.
> It is hard to properly evaluate a precision Voltage source unless you 
> first
> know the measurement uncertainties 'aka noise' including any Temperature
> Coef.
> AND if the temperature coef is known and not zero (over the measurement
> temperatures), why not add a simple compensating voltage to reduce the
> effect of temperature to insignificant levels?
>
> ws
>
> ******************
> ******************
> [volt-nuts] Traveling Standards - Measuring Protocol
> Bob Smither smither at c-c-i.com
>
> I guess it makes sense to define the set of measurements to be made on a
> Traveling Standard and how those measurements are to be made.  I have
> put a draft protocol for making TS measurements here:
>   http://c-c-i.com/tsp
> This is all pretty new to me, so I would appreciate any feedback from
> the list members, especially those that have agreed to make measurements.
>
> Thanks!
> -- 
> Bob Smither, PhD                                 Circuit Concepts, Inc.
> =======================================================================
>


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