By Léa Chazalon and Badr Mesk
July 9, 2026
In a modular electronic system, especially when it is integrated into a chassis with several plug-in boards, the ground is often shared through the backplane. This common ground serves as the electrical reference for all the boards in the system. In theory, all boards are therefore at the same potential. In practice, especially in industrial environments, this is almost never the case.
Industrial installations include motors, drives, power supplies, and long connections that generate potential differences between different ground points. Even a difference of a few volts is enough to create parasitic currents when two pieces of equipment are connected together while sharing a common ground. These currents then flow through paths that were not intended by the designer.
This phenomenon creates what is known as a ground loop. It appears when a board is connected to the system ground through the chassis or backplane, while also being connected to external equipment with its own ground reference. A potential difference between these two grounds causes an unwanted current to flow through the loop formed by the cables and the ground plane.
The consequences can be multiple: noise injected into analog signals, measurement errors, instabilities, false triggering, communication disturbances, or even the propagation of a fault throughout the entire system. In modular architectures, this type of issue can affect several boards at the same time through the common ground plane.
Ground isolation, or floating ground, consists of electrically separating the board reference from the global ground plane. Each board then has its own reference domain. As a result, even if a potential difference appears between the external equipment and the chassis, no parasitic current can flow into the rest of the system. The fault remains localized, measurements remain stable, and the overall architecture is protected.
In demanding environments, ground isolation is therefore not simply a comfort improvement. It is an architectural choice that directly affects measurement accuracy, system robustness, and long-term reliability.
Ground Isolated from the Chassis
Isolation Between the Chassis Ground and the Channel Ground
Excessively fast transitions can generate oscillations, voltage overshoots, and increased electromagnetic emissions due to parasitic inductances and capacitances in the device and its environment. These effects increase electrical stress on the transistor and may reduce its long-term reliability. As a result, switching that is too fast and not properly controlled can offset the expected efficiency benefits.
In a standard configuration, the chassis ground, for example the ground of the rack or system in which the board is inserted, is often common with the signal ground. This can create several problems:
- Ground loops: they generate parasitic currents that introduce noise.
- Electromagnetic disturbances: the chassis can pick up or inject noise into the measurements.
- Potential differences: these can appear between different pieces of equipment connected to the same system.
By using an SMU with isolated ground, the channel ground is decoupled from the chassis ground. This makes it possible to:
- avoid ground loops,
- reduce noise,
- improve the accuracy of low-level measurements, especially low current or low voltage measurements.
Isolated Grounds Between Channels
Why Separate Grounds Between Channels Matter
In a multi-channel SMU, each channel can be used to test a different component or different parts of a circuit. If all channels share the same ground:
- crosstalk can appear,
- a signal on one channel can influence another,
- measurement errors can occur, especially in high-precision measurements.
With separate grounds between channels:
- each channel is electrically independent,
- measurements are more reliable and reproducible,
- it becomes possible to test floating circuits or circuits with different references.
This is particularly important for:
- sensitive component testing,
- precision analog measurements,
- multi-domain systems, for example systems combining analog and power domains.
