By Clarence Klassen
Encoders with the highest possible number of pulses per revolution (PPR) are the most precise, especially at very low speeds. Encoders with the highest PPR are sine/cosine encoders. These use a 2-phase transducer to produce 2 sine waves with 90-deg phase shift between them (sine/cosine). The transducer including the sensor should be perfectly centered, and the phase shift should be perfectly set at 90 degs.
Electronics can be used to compensate for offset.
Electronics can compensate for signal imbalance and gain changes.
Phase errors can be adjusted mechanically or electronically during factory calibration.
A digital circuit can convert the sine and cosine waves to pulses with a very high PPR rate.
Some encoders can provide the equivalent of 4 Mega PPR. This makes for very accurate speed and position measurement. Low-speed velocity control accuracy can be enhanced with these encoders.
Some safe-speed safety drives require the use of Sine-Cosine encoders.