2.4. Grounding Considerations

Chassis vs Measure Common

• Chassis ground: The exterior of the M81-SSM and modules are connected to the chassis ground of the power supply to the M81-SSM.

• Measure common: This internal isolated signal serves as the zero reference for all single ended signals in the system.

Earth ground connections may be made to the M81-SSM via a screw on the rear panel. An earth ground screw is also available on each module. The shell of each BNC connector is measure common.

For flexibility, measure common and chassis ground are isolated in the M81-SSM, allowing them to be joined externally at the point that is best suited for a particular application.

For best performance, chassis ground and measure common should be joined at a single location. If measure common is not connected to earth ground, the system may be more sensitive to electrostatic pickup. If measure common is connected to earth ground at multiple locations, the system may be more sensitive to interference coupled into the system via ground loop. For samples with high impedance, the connection between earth ground and measure common should be located as close as possible to the sample.