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Two different contexts here:

  1. Induction week on the CP Fitters' course. This refers to the first week on your phase 2 course where all the final administration details (like pay, bank details, next-of-kin details and tool kit inspections) are sorted out. During this week, a lot of the health and safety and manual handling training take place.
  2. The ability to produce voltage or current, without physical contact.

For example, in an alternator, passing current through the rotor and spinning it in close proximity to the stator induces, or produces both a voltage across and a current through that stator.

Note: there is no physical contact between the rotor and the stator, they are just very close to each other.

Once this happens, we use the voltage to push the current out to all vehicle electrical loads in order to operate them.

Of course, we can't do this directly, first we must rectify the produced AC to DC and then we must take steps to limit the maximum voltage to around 14.7V.


Inductive sensors like the crankshaft sensor work in a similar way.

Inductive crankshaft sensorWe have a coil of wire wound around a permanent magnet. There is no physical contact between the two, but when the magnetic lines of force from the permanent magnet are made to move, they interact with the windings to produce a voltage across either end of the coil of wire, and a small amount of electricity to flow through the coil of wire.

We make the magnetic lines of force move by spinning a reluctor wheel (mounted on the crankshaft) in close proximity to the permanent magnet.

The reluctor wheel and the permanent magnet are only separated by a very small air gap. As the reluctor wheel spins (because it is mounted on the crankshaft), the soft iron material in the reluctor wheel 'traps' the magnetic lines of force whenever a tooth lines up with the magnet, and 'releases' the magnetic lines of force whenever the tooth moves away and a gap is lined up with the magnet.

Reluctor wheel mounted on a crankshaftAs the crankshaft, and the reluctor wheel which is mounted on it, spins past the sensor, it causes the sensor to produce a sinusoidal wave which is sent back to the engine ECU to be processed. From this electrical information, the ECU can deduce the rotational position of the crankshaft, and the rotational speed of the crankshaft

» Course Glossary

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