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What is an In Vivo Commutator and How Does it Work?

commutatorAn Invivo commutator also known as an electrical swivel, allows for a reliable electrical path in a dynamic rotating system. We can see commutators in many practical applications including inside generators and motors. In preclinical applications the commutator allows an animal to move freely inside the cage while connected to stimulation or recording equipment. The commutator prevents the tangling of cords and the potential distracted behavior of a cable; allowing for more accurate results.

A properly designed commutator is built to maintain consistent and controlled signal integrity. One of the ways to achieve signal integrity is with a slip ring and brush system; a small set of wire brushes are set inside of a conductive metal ring. These brushes should be manufactured in such a way as to keep consistent contact with the ring and ensure low noise with continuous signal path. The best signal integrity is attained by a two brush system. Two brushes on a single ring will increase torque required to rotate the commutator, but will significantly decrease noise. The double brush construction also acts as a failsafe so if one of the brushes slips a ring with use or dirt, the commutator continues to function. A standard double brush setup is commonly used for in vivo studies. One slight variation that has been developed by researcher demand is a single brush commutator. These single brush versions function with similar capability as their standard counterparts, but have a much lower torque requirement. Single brush design is ideal when working with small animals, such as mice, due to their ability to move freely with less torque being applied.

A properly designed commutator is isolated with a good insulating material. The insulation material offers high resistance to creepage and/or clearance voltage potential. Preclinical commutators typically come with a plastic or metal bar which can be mounted onto the top of the cage. Since each setup is slightly different, the bar is generally easily modified so that it works with a variety of setups.

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By: Aubrey Shifflett