Electronics > Metrology

Differential ADC and a 0 to 10V Input Signal

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luky315:
Is it better to "simply" attenuate and buffer a 0 to 10V input signal before measuring it with a 0 to 2.5V ADC (16bit, 100ksps with differential inputs) or is it beneficial to use the differential input of the ADC with a single ended to diff. amplifier (attenuator) like the LTC6363? How do you decide which input stage is more suitable?

Kleinstein:
It depends on the ADC. Some ADCs need a differential driven signal to use there full input range.  Another point is that the INL of some ADC is better with differential drive.
The single ended drive is usually simpler. So if differential drive does not provide a significant advantege one can use a single ended signal.

iMo:
FYI - I've been currently messing with a vintage ADuC845 (2x 24bit SD ADC). Tried all possible settings for the 0-10V usage. Using 2.5V Vref, and an 1:5 resistive divider at the input. Gain set such the input range is +/-2.56V bip or 0-2.56V unip. Floating input voltage (a 10V ref) battery powered. The input ADC voltage is therefore +/- 2V when applied bipolar, or 0-2V unipolar. Internal ADC calibration (zero and gain) made before a measurement. Buffered, chopped, 50Hz rejection, 5.3 smps.

Lessons learned so far - with unipolar you cannot go to 0V. The minimum voltage is something like 0.3V over agnd. That applies for any diff ADCs afaik.

With bipolar I can go +/-10V, the resolution and stddev is 2x worse than with unipolar, there is a difference between the positive and negative 10V readings in my ADC, however, like 300uV (probably INL as specified max 15ppm of FS) but with modern ADCs it could be smaller, hopefully.

luky315:
What would be the "best" solution for measuring a 0 to 10V signal (maybe with some overrange? -0.5 to 10.5V) with 100ksps and > 100 db SINAD?

iMo:
What is your ADC?

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