I designed an analog circuit that transforms a couple of different incoming signals into a digitally compatible signal. I was recently informed there will be a grounding issue at the front of the circuit. The incoming signals will be from a variety of sensors. The first part of my circuit is an op-amp configured as a differentiator to remove dc components of signals. The ground on my op-amp is the same ground as the rest of the analog circuit. I need to factor in the ground from the sensor. Would the easiest way of doing this be to connect the negative of the sensor cable to the grounded opamp input, or use opto-isolation prior to the opamp? My other question is if opto-isolation is the way to go what are the cutoffs as far as the max frequency and min voltage? One of the input signals is a sine wave that increases in voltage as frequency increases, the min voltage I have to consider for this signal is around 50 mV.