I have two ground planes, one of which is connected to Earth (chassis). The other is for PT100 circuitry and is floating, but connected to the body of the PT100. Is there any standard procedure for connecting the two ground planes to minimize static damage from the PT100?
The body of the PT100 is normally not in contact with the 2,3 or 4 wires from the PT100. You can therefore connect the body to ground without any problem and connect the resistor to the input of your system
Frequently the housing is connected to a shielded cable. The wires from the resistor are floating. For proper use the shielding should be connected to ground and the wires to the system.