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Workings of Encoders

Encoders provide speed and positioning feedback. In today's wide range of applications in medical, industrial automation and security, encoders are a vital component for tracking motion in a closed-loop system.

Portescap offers three technologies for feedback and positioning:

Optical Encoders
The Portescap optical encoders offer two-channel quadrature output and and an index pulse. The encoder uses a dedicated ASIC having a matrix of optoelectronic sensors which receive infrared light from an LED after its passage through a metal codewheel. The mask determining the phase angle and index position is directly integrated into the circuit. The light/dark signals are converted into electrical pulses for channel A and B. The channel signals are offset by 90° so that the direction of rotation can be determined. In addition, the standard version of the encoder provides CMOS-compatible complementary signals for improved signal transmission and noise. Integration of this encoder also offers a stand-by mode for reduced current consumption in battery-powered equipment.

Magnetic Encoders
Portescap magnetic Type D and F encoders incorporate a multipolar magnet that is directly mounted on the motor shaft. As the motor shaft turns, magnetic flux variations are detected by hall sensors, which generate two TTL-CMOS-compatible output signals having a 90° phase shift between channel A and B. The rugged design of these encoders makes them ideal for applications that are exposed to severe operating conditions, such as high temperature, dust, humidity and vibration.

Magnetoresistance Encoders
The MR2 encoder uses a bipolar magnet. An MR angle sensor measures SIN/COS magnetic field measurements. An interpolator converts the SIN/COS signals into two square wave output signals (channels A and B). The MR2 technology provides the benefit of high resolution count (up to 512 lines) in a compact design. Also, since the encoder is made around a magnetic angle sensor, it is not sensitive to vertical position changes.

Encoder details

DetailsCharacteristicsAdvantages
Magnetic encoder: P (position sensor), encoder integrated in the motor, position monitored by hall sensorsSimple construction, compact design, two output channelsHigh resolution, two channels, plus home position, signal level very stable, cuts LED supply at stall, no thermal drift
Optical encoder: P+VInsensitive to hostile environments, negligible increase in length of the unit, very low current consumption, high reliability and long lifeVery precise positioning, facilitates counting the number of revolutions, no phenomenon of aging, lower consumption and lower temperature rise, insensitive to temperatures, small dimensions

Additional Information


Magento-Resistive Encoder

Optical Encoder