Magnetic encoders are popular in harsh industrial applications due to the magnetic encoders wide operating temperature range up to 125°C ambient and robustness against shock and vibration.

The magnetic sensor can be a Hall-effect sensor or a magneto resistive sensor, such as an Anisotropic Magneto Resistive (AMR) sensor, which typically have a lower noise than a Hall-effect sensor. However, magneto resistive sensors measure the magnitude of the magnetic field, but cannot sense the direction. Therefor additional sensors, such as digital Hall switches are required to extend the measurement range to 360°.

For motor integrated encoder applications with the magnet mounted at the end of shaft, on-axis sensing with two ARM sensors which are 45° rotated against each other are well designed.

The electrical signal chain offset and gain mismatch as well as sample rate, speed and resolution of the analog to digital converter impact the accuracy of the measured absolute angle and components with very low temperature drift help reduce the angle error. Decoding of the angle from the sine and cosine sensor signals require math functions such as division, multiply-and -accumulate and arc tangent.

Small footprint circuits with high integration and low power consumption are critical to design smallest form factor circular PCB of less than 30mm diameter. Since the encoder can be motor integrated, ambient operating temperatures at least up to 125°C are typically required.

The absolute encoder RS485 communication interface need to be designed for high EMC immunity to minimize bit errors during the data transmission.