[volt-nuts] Best Vref part ?

[Andreas Jahn]

Hello Fred,

do you want to have a stable voltage (calibrator) or do you
want to use this reference with an ADC for precise measurements?

I tried many 5V-references for an 24Bit LTC2400 ADC.
>From LT1027, LT1021 and LT1236 the LT1027 is the best.
Similar performance I have found with a MAX6250A but
my device seems to have some popcorn noise of around 1-2 ppm.

I use a simple NTC temperature sensor to do a 3rd order
polynomal compensation of the tempco of the reference.
(see picture on 09.09.2011 in this list).

I use LT1027CCN8-5 references and the stability after ageing
is mainly determinded by relative humidity. (0,4 ppm / % rH)
after having calculated the tempco out of the reading.
Ageing is less than humidity influence during the last year.
The references are now running since 3 years.

To get humidity factor off  I buyed 2 hermetically tight
 VRE3050AS from Digikey. But with my 2 devices
have horrible noise (factor 3-5 over LT1027).
Hysteresis I have measured on the first of the
2 VREs and found 4-5ppm compared to
the LT1027 with about 1-2ppm.

With best regards

Andreas

----- Original Message ----- 
From: "Fred Schneider" <pa4tim at gmail.com>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Friday, September 30, 2011 9:49 AM
Subject: [volt-nuts] Best Vref part ?


>I want to make some good ( better then the ones I made) Vrefs. Better as in 
>longtime stability and tempco. Just for fun.
> The ones I made upto now have a short time drift of 1 to 3 ppm, longtime 
> ?? They are on for a month now, and begin t ostabilize.
> I have the schematic from Warren that uses the 1n825, i can buy that from 
> Farnell.
> I have a schematic that uses a LT1021B, also for sale at Farnell.
> But I have read about LM199/299/399 that is temperature controlled
> LTZ1000 that should be very good and VRE4100 but non of those sold by 
> Farnell.
> What is the best option ? I am not a company so I can not order 
> evereywhere. I can buy from R&S, Farnell and Conrad. I have no ebay acount 
> because I do not like auctions and bidding.
>
> Fred PA4TIM
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