Advantech RS-485 user manual Normal Mode and Common Mode, Figure F-3 Normal mode and Common mode

Appendix F

1.3 Normal Mode and Common Mode

Figure F-3: Normal mode and Common mode.

Have you ever tried to measure the voltage between ‘Hot’ and concrete floor, or measure the voltage between ‘Neutral’ and concrete floor? You will get nonsense value with above testinF. ‘Hot’ and ‘Neutral’ were just a relational signal, so you will get the AC110V or AC220V by measure those two signal. Normal mode and common mode just show you that the ‘frame ground’ is the most important reference signal for all the systems and equipments.

ADAM-5000 F-5