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Grounding of detectors and their electronics

Grounding of detectors and their associated electronics is a complicated and delicate problem in large experiments. The general aim in grounding is to prevent the pick up of noise in sensitive signal connections. Ground loops can potentially between sub-systems can generate parasitic currents  which can seriously degrade the correct capture of small signal levels from the detectors. The communication between different parts of the system can also be seriously affected by the build up of common mode voltage difference ( for copper links). In some cases safety regulations for the use of power supplies (especially high voltage) can impose rules that makes it impossible to design the perfect grounding scheme.

Existing documents:

EDMS 584310, Grounding, Shielding and Power Distribution in LHCb

EDMS 473833, Grounding network in LHCb.

EDMS 478224, Electrical distribution network for the LHCb experiment.

EDMS 473770, Mains power requirements for the LHCb experiment.

Links to drawings:

Grounding in the counting house

Grounding of equipment

Grounding of the rails

LHCb grounding and EMC workshop

General points to be aware of:

  • All structures must be connected to safety ground.
  • Prevent ground loops via sensitive signal paths
  • Use galvanic isolated links when ever possible.
  • Use differential electrical links (if optical not possible) and insure sufficient common mode range to reject noise and ground potential differences.
  • Use shielded cables when ever possible.
  • Take special care of high voltage and its distribution.
  • No single point failure must generate safety hazards ( e.g. high voltage connected to accessible structure).
  • Use floating low voltage power supplies.
  • Be aware the ECS interfaces based on I2C or JTAG can introduce ground loops as these signals are single ended.
  • Linear voltage regulators does NOT give galvanic isolation.
  • Distribution of power from large bulk power supplies (e.g. Wiener Maraton) will give specific grounding problems.

More Information

F. Szonsco from CERN has made a web page on EMC

F.Szonsco gives a course on EMC problems. His lectures are available directly on the web.

CMS EMC web page.


Alice has a preliminary grounding policy

This page was last modified by JC on 16 May, 2006. This page has been accessed Hit Counter number of times.