What is an Inductive Encoder?

An inductive sensor is a non-contact sensing technology that works using transformer principles to measure position or speed.

 In recent years, a new generation of device has become popular – the inductive encoder. Inductive encoders can be thought of as a hybrid of a resolver and an optical encoder. Inductive encoders (or Incoders) use the same basic physics as a resolver but are less costly, lighter, more compact and more accurate. Importantly, they are also easier to use because they only require a DC supply and output a digital signal representing absolute angle – like an absolute optical encoder. The skills issue is eradicated because inductive encoders do not require separate electronics processing circuitry – all the necessary electronics are integrated in the inductive encoder’s stator. This means that Incoders have all the advantages of resolvers but with none of their disadvantages. Because inductive encoders do not use delicate optical components, they are not susceptible to foreign matter and do not only operate in limited temperature ranges. Indeed, in some instances they have been used at temperatures of up to 230 deg C. Rather than the traditional resolver’s copper wire windings, Incoders use printed circuit boards as their main components. As with a resolver, there is a stator and a rotor but because there is no requirement for precise location of the stator and rotor, there is no need for any bearings. Since Incoders use printed circuit boards rather than wire windings, this means that they can offer extremely high accuracy. Accuracies of <1 arc-minute are common, as are resolution and repeatability of <1 arc-second. The basic design of an Incoder also means that it can be readily customised to suit a particular application’s requirements. Incoders are available in a wide range of sizes up to 600mm diameter and have been used extensively in a variety of machine tools, gimbal systems, aerospace, defence and medical equipment.