position at any one time. The Gray code is often used. This code can be read by a controlling device, such as a microprocessor or microcontroller to determine the angle of the shaft. The absolute analog type produces a unique dual analog code that can be translated into an absolute angle of the shaft. Magnetic absolute encoders The magnetic encoder uses a series of magnetic poles (2 or more) to represent the encoder position to a magnetic sensor (typically magneto-resistive or Hall Effect). The magnetic sensor reads the magnetic pole positions. This code can be read by a controlling device, such as a microprocessor or microcontroller to determine the angle of the shaft, similar to an optical encoder. The absolute analog type produces a unique dual analog code that can be translated into an absolute angle of the shaft (by using a special algorithm). Due to the nature of recording magnetic effects, these encoders may be optimal to use in conditions where other types of encoders may fail due to dust or debris accumulation. Magnetic encoders are also relatively insensitive to vibrations, minor misalignment, or shocks. Brushless motor commutation Built-in rotary encoders are used to indicate the angle of the motor shaft in permanent magnet brushless motors, which are commonly used on CNC machines, robots, and other industrial equipment. In such cases, the encoder serves as a feedback device that plays a vital role in proper equipment operation. Brushless motors require electronic commutation, which often is implemented in part by using rotor magnets as a low-resolution absolute encoder (typically six or twelve pulses per revolution). The resulting shaft angle information is conveyed to the servo drive to enable it to energize the proper stator winding at any moment in time. Capacitive absolute encoders An asymmetrical shaped disc is rotated within the encoder. This disc will change the capacitance between two electrodes which can be measured and calculated back to an angular value. Absolute multi-turn encoder A multi-turn encoder can detect and store more than one revolution. The term absolute multi-turn encoder is generally used if the encoder will detect movements of its shaft even if the encoder is not provided with external power. Battery-powered multi-turn encoder This type of encoder uses a battery for retaining the counts across power cycles. It uses energy conserving electrical design to detect the movements. Geared multi-turn encoder These encoders use a train of gears