One Ground loop A ground loop occurs when multiple devices within a measurement or automation system are connected to each other via different ground points. Small or even significant potential differences can arise between these ground points, leading to unwanted equalizing currents.
In typical measurement applications, sensors, measuring instruments, data loggers, controllers, and computers are often connected to one another both via signal lines and through their respective ground connections. If the ground points are not at the same electrical potential, equalizing currents flow through the signal or communication lines. These currents can superimpose on the actual measurement signals and thereby cause measurement errors.
Potential differences can arise, among other things, due to:
- Large spatial distances between plant components
- High-Power Electrical Loads
- Electromagnetic fields from nearby facilities
- High-voltage power lines in the area
- Switching Operations in Industrial Networks
- Lightning and Surge Effects
Ground loops can significantly impair measurement quality, particularly when measuring small analog signals such as temperature, pressure, force, or strain. The effects range from signal noise and offset errors to unstable or completely distorted measurement values.
An effective way to prevent ground loops is to consistently galvanic isolation of the signal paths. Modern Delphin measurement and data acquisition systems feature comprehensive galvanic isolation at the inputs and outputs. This effectively prevents unwanted compensation currents and ensures high measurement accuracy even in demanding industrial environments.
In addition, we recommend using sensors that do not require grounding as well as proper shielding and wiring of all signal and communication lines. Faulty shielding designs or multiple shield connections can, in turn, cause new ground loops.
Typical consequences of ground loops:
- Falsified Measurement Values
- Signal-to-noise ratio and interference
- Drift and Offset Errors
- Communication Problems in Bus Systems
- Unstable Measurement and Control Processes
Measures to Prevent Ground Loops:
- Use of Galvanically Isolated Measurement Systems
- Use of Sensors That Do Not Require Grounding
- Proper Shielding of Cables
- Avoiding Multiple Grounding Paths
- Careful Planning of Equipotential Bonding and Grounding
Avoiding ground loops is an important aspect of industrial measurement and automation technology. Only through a proper grounding and wiring strategy can measurement signals be reliably acquired and consistently and accurately evaluated.