[volt-nuts] Homebrew DVM

[Andreas Jahn]

Hello Randy,

with a capacitive divider 2:1 or 3:1 based on a LTC1043 + LT1051
you can extend the 5V range to 10 or 15 V. The capacitive divider
is very stable over temperature and time.

With my 2:1 dividers I have less than 1 ppm drift over a
10-40 degrees (celsius) temperature range.

Absolute accuracy of the divider factor depends mainly on
charge injection of the switch and capacitor losses.
I measured values between 2-10ppm depending on different
pin configurations. Im not shure wether the examples in the
datasheet are using the correct pin numbers for minimum charge injection.

Another Question: how do you get a unipolar 0..5V range with a ADS1282?
The absolute input of the PGA-Amplifier is specified from 0.7 .. 3.75V.

With best regards

Andreas


----- Original Message ----- 
From: "Randy Evans" <randallgrayevans at yahoo.com>
To: "Михаил" <timka2k at yandex.ru>; "Discussion of precise voltage 
measurement" <volt-nuts at febo.com>
Sent: Friday, November 11, 2011 5:01 AM
Subject: Re: [volt-nuts] Homebrew DVM


> The ADS1282 alswo only has a 5V unipolar input range and I want a 0 to 12V 
> input range without dividers. I don't have any information on the 
> Solartron 7081.
>
> Randy
>
>
> ________________________________
> From: Михаил <timka2k at yandex.ru>
> To: Randy Evans <randallgrayevans at yahoo.com>; Discussion of precise 
> voltage measurement <volt-nuts at febo.com>
> Sent: Thursday, November 10, 2011 9:17 AM
> Subject: Re[2]: [volt-nuts] Homebrew DVM
>
> Hi, Randy!
> AN-260 is a very bad example of slow medium scale ADC.
> I think that 130 db SNR ADS1282 is much better. Also, 8,5-digit Solartron 
> 7081
> have a simple and cheap delta-sigma ADC with 0.06 ppm noise and 51 sec.
> integration time.
>
>
> Mickle T.
>
> Thursday, November 10, 2011, 8:20:58 PM, you wrote:
> RE> 8.5 digits with averaging.
> RE>
> RE> I did consider that but the ADCs I am familiar with only have a 5V 
> input
> RE> range so range resistors would be required, not desirable for me. 
> Also,
> RE> they won't directly take the 7.2V ref input from a LTZ1000. Plus the 
> AN-260
> RE> circuitry is not too complex. Otherwise, I agree with you.
> RE>
> RE> Randy
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