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!