High Resolution Encoder

A high resolution encoder is typically a rotary or angle encoder with a resolution of >10,000counts per revolution (cpr) and often >100,000cpr. For incremental encoders, with A/B pulse style outputs, resolution is specified as 4x the number of pulses per rev since there are 2 edges to be counted per each pulse in the A stream and 2 edges on each B stream pulse. For absolute encoders, resolution is usually stated as the number of measurement bits per revolution – for example 18bits or 262,144cpr; 19 bits or 524,288cpr and so on.

High resolution encoders are usually required for precision control of speed and/or position – especially when control at very low speed is required. A classic example is angular motion control of pointing devices such as cameras, telescopes, radar or weapons systems. These must be directed at distant but moving targets and this requires precise but slow control of the (azimuth or elevation) drive motors.

Inductive encoders or ‘IncOders’ are well suited to such applications with resolutions of up to 22bits or roughly 4Mcpr as standard. Notably, Zettlex IncOders specify a repeatability of +/-1LSB (least significant bit) which means that their specification shows true resolution. This should be compared with other (capacitive) encoders where high resolution is stated but, in practice, the true resolution is much lower since the least significant bits suffer from high noise or flicker.