///////erik malund:: Bro you reply so fast like a 10Mbps Rs485 link Ya you have made me intelligent in 485 communication \\\

in an aeroplane (or car for that matter) you connect to frame.
/////// I plan to use this for a Bus Road transport . RS485 cable runs from its HVAC unit to its Engine .The body of the bus or its frame is not at 0v ,or -ve of battery The battery is floating I dont know why ? .I am getting power from a DC/DC( 24Vdc) converter which it self is Floating Should I tie the shield to its body or to my circuit common ,Inside my cable I plan to run T+ ,T-,+24v and 0v .\\\\

Where does majority of designs tie the Shield PE or 0V?
at the point with least resistance/inductance to PE or 0V

////// RANDOME RANDOME Please show me how to find this can we use multimeter or we have to calculate this , I'm also confused with when you use GND is this the one for Circuit common or/and the circuits internal reference 0v \\\\\

Please note this I understand ::::
PE = Earth is dug and a Rod is placed and connected.
Circuit Common or 0v = internal circuit reference .

Kindly/