Magnetic vs Optical
Leading Rotary Encoder Manufacturer POSITAL FRABA take a look at the
differences between two main encoder technologies
Magnetic rotary encoders determine angular position using magnetic field sensor technology. A permanent
magnet (1) is fixed to the encoders’ shaft and creates a magnetic field that is in turn sampled by a sensor (2) that
generates a unique absolute position measurement.
POSITAL’s IXARC magnetic encoders can perform at the performance level of optical systems due to a new
generation of sensor systems. The combination of a custom Hall-effect sensor and complex signal processing al-
gorithms running on a powerful 32 bit microprocessor, results in a significantly improved resolution and accuracy,
along with a minimal latency of only a few microseconds.
Multiturn measurements are achieved by means of a rev-
olution counter system that uses an energy harvesting system
based on the Wiegand effect. This system requires no gears or
batteries. Eliminating batteries brings about many advantages
over traditional multiturn solutions. Batteries have a limited
lifespan, weigh a lot, and often contain harmful substances.
Gear units also have disadvantages of their own being large,
complex, costly and vulnerable to shock and vibration.
Robust
and durable
Magnetic
Advantages
Regardless of the rotational speed, even at near-zero, the energy harvest-
ing system generates short, powerful voltage pulses, sufficient to power the
counting electronics. The result is a revolution counter that is independent of
any external power supply. This technology, which has been proven for over 12
years enables maintenance-free reliable measurement of absolute positions,
even in demanding environments .
• Robust and durable
• Mechanically simple and
economical − no battery,
no gears
•Compact design for instal-
lation in small spaces
A key component of optical rotary encoders is a code disk (1) which is mounted on the encoder shaft (2) . This
disk is made of high durability plastic that has a concentric pattern of transparent and opaque areas. Infrared light
from an LED (3) shines through the code disk, onto an array of photoreceptors. As the shaft turns, a unique com-
bination of photoreceptors are illuminated or blocked from light by the pattern on the disk. For multiturn models,
there is an additional set of code discs arranged in a gear train (4) . As the main encoder shaft rotates, these discs
are geared together to turn like the wheels of an odometer. The rotational position of each disc is monitored opti-
cally and the output is a count of the net number of rotations of the encoder shaft.
POSITAL’s IXARC optical absolute rotary encoders use highly
integrated Opto-ASICs, providing a resolution up to 16 bits
(65,536 steps) per turn. For multiturn models, the measuring
range is extended by the mechanically geared code disks to
as many as 16,384 revolutions.
Optical Advantages
•High resolution, accuracy & dynamic response
•For use in areas with high magnetic fields
•No risk of these devices losing track of their absolute
position
•No backup batteries required
POSITAL exclusive UK & Ireland sales partner
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