The commutator is responsible for the reversal of electrical polarity. It is also called the reversal switch. To safeguard an optimal function, some parameters are of particular importance. Compliance with defined surface roughness ensures good contact between the commutator and the contact brushes while keeping wear at a minimum.

Precise roundness and runout characteristics of the entire disc sets are important parameters. The segment distance can be determined with a formtester as well as with special measuring devices. Testing is required since segment distances that are too large foster the formation of sparks between carbon brushes and commutator, thereby increasing wear. This in turn has a significant influence on the life of the engine.

	MarForm Commutator analysis	MarSolution RPM
Segment gap: segment center DCL; max./min. radius BTB
Segment gap: difference between max. radii
Segment gap: end of segment - start of segment STS
Roundness deviation with corresponding angle position
Roundness deviation Mean value of all individual roundness
Total roundness deviation (RONt)
Radial runout
Delta to Bar DTB and Max Bar DMB
Straighten-up Delta Bar DBR
Local Form Default EFL
Diameter collector