Bipolar signal used in differential ADC
Here is an approach that condenses the other answers into a practical circuit. It is just a single-ended to differential converter.

It first divides the input voltage to put it in range of the amplifier, and then amplifies it again to provide the input to the ADC. Note that this is basically the same as a gain of 1 configuration (that can be obtained with an LTC1992-1), but using external resistors allows for negative voltages on the input side of R4 &amp; R5.



For best accuracy and low-noise make sure to connect the grounds as indicated (the 0.001Ω resistor is just to join the nodes, it's not a real component). Preferably use a twisted pair for the signal connection.

This is the output of the circuit:



Additional filtering (a second pole) can be added by placing capacitors in parallel with R6 &amp; R7. It should be possible to combine R1 &amp; R4 as well as R2 &amp; R5 for a somewhat simpler circuit in this case.