Hi Melanie,

This is my explanation:

1.The J3.1 is the incoming signal(iV) that i want to measure, so i connect it to RA4.
2.The iV also connect to a relay at NC. At the normal operation mode, the iV will connect to J3.2 via the NC on Rly2.
3.In abnormal operation mode, the voltage signal from RB.3 will connect to J3.2 via the NO. That means the Rly2 need to be on and the iV need to be cut off from connecting to J3.2.
4.The RB.3 output signal will also based on the iV but with some amendment before PWM on RB.3.

Thanks!