How to add dc bias to ac signal?

Other Hardware Science and Measurement
1

I want to measure ac signal (ranging from +2.5 to -2.5 V) using arduino. How do i add a dc 2.5V to the ac signal so that it ranges from 0 to 5V ?

2

Describe the signal source. Depending on the source characteristics, a voltage divider similar to this will work:

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3

But that circuit is assuming a balanced signal, which might not be the case (for instance a
signal composed of short 2.5V pulses with the normal level -2.5V would fail with the above
circuit).

A sinusoidal signal would be fine, but you need to add a 1k or so in series with the analog
pin to limit current on initial transients.

An opamp in differential-amplifier configuration is a good solution for level-shifting and
scaling analog signals accurately.