An encoder measures movement or position.
A rotary encoder converts shaft rotation into electrical information. Optical and magnetic designs are common; their operating principles and interfaces differ.
The receiving system interprets the signal. An encoder attached to a motor measures at that shaft, not directly at every part of the lift.
Incremental encoders report changes.
- Shaft rotatesA repeating pattern passes the sensing elements.
- Signals changeChannels produce a sequence of transitions.
- Controller countsMovement and direction are derived from the sequence.
Be clear about the counting convention.
If a receiver counts all four edges of quadrature channels A and B, it records 4,096 counts per revolution. Other counting modes give different totals.
Pulse, cycle and count are not always used consistently between specifications. Resolution describes distinguishable increments; it is not the same as accuracy.
Absolute encoders identify a position.
An absolute encoder provides a position value within its measuring range. Single-turn devices identify angle within one revolution; multi-turn arrangements also distinguish revolutions within their range.
Having an absolute motor angle does not automatically identify the lift’s floor. The system still needs the relationship between that measurement and the installation.
Feedback must represent the intended motion.
Mounting, coupling, signal quality and compatible interfaces matter. An encoder can report its own movement correctly while a loose mechanical connection prevents it from representing the intended shaft.
Position changes over time give speed information. The next lessons show how a drive uses that information to influence motion.
A closer look
An incremental system generally needs a reference or retained position information to know an absolute location. An index pulse can mark a point in each revolution but does not by itself identify which revolution the machine is on.
Check your understanding
Does a higher encoder resolution automatically mean equally high positioning accuracy?
Reveal the explanation
No. Resolution is the size of distinguishable increments. Accuracy also depends on the sensor, mounting, mechanics and interpretation.