| ??? 07/09/08 13:02 Read: times |
#156555 - If ... Responding to: ???'s previous message |
If you do not connect chassis ground to signal ground (at least by a cap, for high frequencies) then the chassis cannot act as a shield! Shielding means to force the shield's potential to the same potential as signal ground, so that no interference can be injected from the shield (hitted by interference) into parts of the circuitry via unavoidable stray capacitance. So, you always need to use at least a cap between signal ground and chassis ground.
Here is a schematic how PROFIBUS handles the RS485 signals including the bus's signal ground with respect to chassis ground at each node: 
Kai |
| Topic | Author | Date |
| RS485 on straight wires? | 01/01/70 00:00 | |
| terminate with the "characteristic impedance" and | 01/01/70 00:00 | |
| Possible | 01/01/70 00:00 | |
| No so good | 01/01/70 00:00 | |
| The idea of pairing and twisting... | 01/01/70 00:00 | |
| Telephone Cable... | 01/01/70 00:00 | |
| If not straight wires | 01/01/70 00:00 | |
| sorry Per | 01/01/70 00:00 | |
| it's okay | 01/01/70 00:00 | |
| We use Cat-5 cables... | 01/01/70 00:00 | |
| ESD | 01/01/70 00:00 | |
| Which end? | 01/01/70 00:00 | |
| If ... | 01/01/70 00:00 | |
485/422/profibus | 01/01/70 00:00 | |
| 485 cable | 01/01/70 00:00 |