Key Differences Between Rotary Encoders and Linear Grating Scales

Rotary encoders and linear grating scales are common position sensors. This article explains their main differences to help you choose the right sensor for rotation or linear motion measurement.

Rotary encoders measure rotation and are typically mounted on a rotating shaft. They come in absolute and incremental types: absolute encoders retain position after power loss, while incremental encoders report relative changes and require external zeroing. Linear grating scales measure linear displacement using an optical or magnetic scale and a read head; they generally offer higher accuracy and resolution for linear motion.

Installation differs: rotary encoders mount on shafts, while linear scales require careful attention to guideway flatness and straightness. Rotary encoders are suitable for applications needing continuous 360° measurement; linear scales are suited to high-precision linear positioning such as CNC machines and printing equipment.

Cost and application range also differ: rotary encoders are usually less expensive and meet general rotational measurement needs; linear grating scales are costlier but meet higher linear precision requirements. Choose the sensor based on application demands and accuracy requirements.