# How would I go about measuring an analog signal that has both positive and negative voltages on an arduino analog pin at a high sampling rate?

I have a signal that fluctuates between -70mV and 50mV. How would I get the arduino mega to read this on an analog pin at a high sampling rate? Ultimately I am trying to graph the data in real time so it looks like this.

I have looked at the question posted earlier on EESE about reading positive/negative voltages and it gives info on a slow moving signal that ranged from -55V to 55V. I doubt this solution would apply to my situation though (attenuating signal with two resistors and then offsetting the range by using an op-amp summing circuit).

• Try using an instrumentation amplifier like the INA282 (it's designed as a current sense amplifier, but all it really does is amplify the signal by a fixed amount and level-shift it to be centered around an input voltage, after all) – Hearth Oct 11 '18 at 21:33
• You would buffer the acquisition, and plot it in pseudo-real time – Scott Seidman Oct 11 '18 at 21:43
• Just curious. Your text says $\text{mV}$. Your chart shows $\mu\text{V}$. That's only three orders of magnitude difference. Which is it? – jonk Oct 11 '18 at 21:52