Magnetic position sensor replaces optical rotary encoders

March 17, 2015 // By Graham Prophet
Unparalleled accuracy over full temperature range at high speed is claimed for the latest version of ams’ 47 series; the AS5047P with incremental ABI output is a replacement for optical encoders and resolvers in motor and motion control systems, enabling lower system costs while providing high accuracy performance

ams has a new version of its 47 series of magnetic rotary position sensors for motor and motion control applications, featuring higher rotation speeds and higher-resolution incremental outputs. AS5047P features ams’ DAEC (dynamic angle error compensation) technology, which produces very accurate angle measurements even at very high rotation speeds. The 47 series magnetic sensors’ high-speed performance and ABI incremental outputs make them ideal as robust replacements for optical encoders. The total system cost of a design based on the 47 series is also normally far lower than the cost of an equivalent optical encoder or resolver.

In the AS5047P sensor, the maximum rated measurement speed has been increased from 14,500 rpm to 28,000 rpm, thus enabling it to support many high speed rotating shaft applications that previously could only be addressed with optical encoders.

ams has also increased the number of steps per revolution in the device’s incremental ABI outputs. The 47 series’ ABI outputs are equivalent to the outputs of a standard optical encoder, so motor control system designers can replace an optical encoder without any change to their control software or interface. In the AS5047P, the maximum resolution of the ABI output is raised to 4,000 steps/1,000 pulses per revolution in decimal mode, and 4,096 steps/1,024 pulses per revolution in binary mode, which means that a wider range of optical encoders can now be replaced.

A standard four-wire SPI serial interface allows a host microcontroller to read 14-bit absolute angle position data from the AS5047P, as well as to program non-volatile settings without the need for a dedicated programmer. The device also simultaneously provides a standard UVW commutation interface for use in brushless DC motors, eliminating the need for discrete Hall sensor switches, and providing a single IC to support both motor position and control applications. The absolute angle position may be provided as a PWM-encoded output signal.

AS5047P is highly immune to interference from stray magnetic fields,