Question
I would like to ask you what does the Temperature drift in the ADE7758
datasheet mean.
In page 5 of 72 the temperature coefficient of the Voltage reference is 30
ppm/°K typical. That should mean that reference voltage increases as
temperature rises and therefore that any voltage at T=20°C should be less than
what measured at T=80°C, isn't it?
Are there any other drift in the ADE (for example PGA) that are not included?
I'm asking those question becaus I'm trying to dimension my resistance to
obtain the minimum temperature drift.
Answer
I would not assume that the reference drift is necessarily positive with
increasing temperature. The specification is ambiguous, but I would interpret
30ppm/degC as either positive or negative.
The overall effect of temperture on reading error is shown in the plots on
pages 12 to 16. Some plots include the error arising from the internal
reference while others exclude the internal reference error (the external
reference is assumed to be "perfect")