See Ground Return & Common Impedance Coupling
When two circuits share a common ground, the ground voltage of each one is affected by the ground current of the other circuit.
![](/EMCFLEXBLOG/image.axd?picture=/2020/TUTORIAL/common_return_supply_path.png)
When two circuits share a common power supply, current drawn by one circuit affects the voltage at the other circuit.
![](/EMCFLEXBLOG/image.axd?picture=/2020/TUTORIAL/common_power_supply.png)
27. January 2020 09:26 by Christian in
EMC/EMI, Load Simulator Understanding the role of return ground is essential in EMC testing.
VISIT OUR NEW EMC LAB BLOG
See Differential Mode vs Common Mode Current
![](/EMCFLEXBLOG/image.axd?picture=/EMCLAB/PNG/RETGND/Current Return_1.png)
![](/EMCFLEXBLOG/image.axd?picture=/EMCLAB/PNG/RETGND/Current Return_2.png)
![](/EMCFLEXBLOG/image.axd?picture=/EMCLAB/PNG/RETGND/Current Return_3.png)
![](/EMCFLEXBLOG/image.axd?picture=/EMCLAB/PNG/RETGND/Current Return_4.png)
![](/EMCFLEXBLOG/image.axd?picture=/EMCLAB/PNG/RETGND/Current Return_5.png)
Christian Rosu, Flexautomotive.net, 2020-01-27