The Rise of High-Resolution Magnetic Encoders: A Short History

Rotary encoders provide position feedback in all sorts of systems. The demand for encoders continues to grow as customers demand higher efficiency and smarter motion control.

In the beginning
In the old days, encoders were baseball-sized metal cans containing a glass disk with opaque metal lines. Other parts included a set of bearings and a shaft used to mount the glass disk. One side of the disk had an incandescent or LED light source and lens assembly; the other reverse had a metal grating mounted in front of two or three light sensors.  

These encoders were expensive and subject to failure due to bearing life, shock and aging of the light source. In an effort to reduce cost and improve reliably, kit encoders were developed. They eliminated the need for encoder bearings by mounting the optical disk directly on the motor shaft. The optical unit was then mounted from the side of the optical disk, making sure to position the disc precisely between the light source and sensor array. This worked well as long as the motor had little end play and the environment was free of dust, dirt and condensation.

Also around this time, Hall effect or magneto resistor-based magnetic encoders were available. They had very low resolution or very tight air gap tolerances. Despite these drawbacks, they filled a need where high shock loads, high temperature and contamination from dust, dirt, oil or condensation were a problem.  

Sensors and encoders today
Today, magnetic kit encoders use chips that combine an array of Hall effect sensors and signal processing electronics to provide signals that are 100-percent compatible with traditional quadrature encoders. Magnetic kit encoders such as the M15 product line from Timken produce high resolution A and B quadrature signals as well as optional once-per-turn reference pulse and U, V, W commutation signals. Magnetic kit encoders are cost effective and operate with a larger range of assembly tolerances than similar optical encoders. Being magnetic rather than optical, they excel where high shock loads, high temperature and contamination are a concern.

Need help selecting the proper encoder technology for your applications? Give us a call at 603.358.4760 or send us an email, we’d be happy to help!