PVDF charge amp help

I am currently trying to build a charge amp for a PVDF vibration sensor. I am using the OPA111 and have a circuit diagram, attached. I am having a problem understanding the reason for wire coming out of pin 8? And how to wire this up as it looks like it wants me to earth pin 8 and the negative op amp input.

I have never come across this before so if someone could explain, that would be great.

hi,
Its the substrate and should be connected to Common.
On your circuit pin8 is connected to the Screen of the input cable, close to the OPA111