[volt-nuts] Traveling Standards - Measuring Protocol

Mitch Van Ochten mitch at vincentelectronics.com
Thu Sep 8 00:48:18 UTC 2011


What type of averaging did you do for the light blue trace?


Regards,

mitch

----- Original Message ----- 
From: "Andreas Jahn" <Andreas_-_Jahn at t-online.de>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Wednesday, September 07, 2011 1:45 PM
Subject: Re: [volt-nuts] Traveling Standards - Measuring Protocol


>> 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
>>
>
> Tempco measurement will be essential for the MAX6350.
> For the LM199 I have made the experience that over a
> 10 to 40 degree (celsius) temperature range there will be
> around 1 ppm of change. Of course its better to know
> the exact values. So its easier to trace back the current measurement.
>
>
> First picture MAX6250A (which is similar to the MAX6350)
> used as voltage reference of a LTC2400 measuring
> my LM399 #2 with a LTC1043 based precision voltage divider
> over temperature range 10 - 40 degree celsius.
> Y-axis is 2:1 divided voltage in mV.
> You can clearly see the hysteresis of the plastic device.
> And you can see a "hysteresis jump" near 39 degrees of around 1 ppm.
>
> Attached you see a plot of my LM399 #2 over temperature
> as difference to my LM399 #1 at room temperature.
>
> recorded is
> red: difference voltage in mV LM399 #1 - LM399 #2
> light blue: same but averaged to get the noise out
> green: environment temperature of LM399 #2 housing
> dark blue: within LM399 #2 housing
> yellow: environment temperature of LM399 #1
>
> so the change is around 7uV when regarding the averaged value.
> and most of the "tempco" seems to be off the temperature
> gradient (thermo voltages) and not from the actual temperature.
>
>
> With best regards
>
> Andreas
>


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