The incremental encoders are constructed according to optical or magnetic principles as well as in a single-chip version. Available at the encoder outlets are two 90°e phase-shifted square wave signals with up to 10,000 pulses as well as one index pulse per motor revolution in the 3-channel version.
Incremental encoders transmit a specific number of uniformly distributed lines per revolution. All FAULHABER Incremental encoders have at least two channels: A and B. Both channels supply a square wave signal, shifted by 90°e with respect to one another, i.e., one quarter cycle C. Through this shift of the pulses, the motor’s direction of rotation can be determined.
Functionality of incremental encoders
An incremental encoder does not measure absolute positions, but rather relative positions. So incremental encoders determine a position relative to another reference position. For this purpose, the signal edges must be counted forward or backward by the motor control using a quadrature counter according to their edge sequence.
This position value of an incremental encoder, however, will be lost if the power supply is interrupted. A positioning system must therefore move to a defined reference position during commissioning or after a power interruption to initialise the position counter. This process of an incremental encoder is referred to as homing. For the determination of the reference position in incremental encoders, an additional, external sensor, such as a reference switch or limit switch, is usually used.
Incremental encoders from FAULHABER - Features and benefits
To determine the reference position with an especially high level of accuracy, the FAULHABER 3-channel incremental encoders have an additional channel – the index. Here, a single index pulse is generated once per revolution. External reference switches or limit switches can have a comparably high position error due to environmental influences and can sometimes trigger a little earlier, sometimes a little later. To nevertheless accurately determine the reference position, the drive system can move back after the limit switch until the first signal edge of the index pulse occurs. This point can then be used as an exact reference position.
Incremental encoder with integrated Line Driver
Some of the FAULHABER incremental encoders are equipped with a Line Driver. The Line Driver generates an additional differential signal Ā , B̅ and Ī for all channels, A, B and I. Electromagnetic interference in incremental encoders can thereby be eliminated using this method during signal transmission. Especially if the encoder signals must be transmitted over long distances of 5 m and more and for position control, the use of a Line Driver is recommended.
On the control side, these differential signals of an incremental encoder must be combined again with a receiver module. The Line Drivers from FAULHABER are TIA-422 compatible. TIA-422, also known as EIA-422 or RS-422, is an interface standard for cable-based, differential and serial data transfer.
Incremental encoders of the IER3-10000 (L) series consist of a high-resolution code disc that is attached to the motor shaft, a light source and a photo sensor with interpolator as well as driver stages. The light from the light source is reflected or absorbed by the code disc. The reflected light is collected by the photo sensor of the optical incremental encoder and the signal processed into a high-resolution encoder signal. Two square wave signals that are phase-shifted by 90 °e, as well as an index signal to display output shaft rotation are then available at the output. A Line Driver is optionally available for this series of incremental encoders. The high-precision optical encoders are ideally suited for position control.
- Very high resolution of up to 40 000 edges per revolution (corresponds to a 0,009° angle resolution)
- Very high position accuracy, repeatability and high signal quality
- Various resolutions available as standard feature
- Insensitive to magnetic interference
Incremental encoders of the IE3-1024 (L) series consist of a diametrically magnetized, two-pole sensor magnet which is fastened to the motor shaft. A special angle sensor for detecting the motor shaft position is positioned in an axial direction in relation to the sensor magnet. The angle sensor of the magnetic incremental encoder comprises all necessary functions, such as Hall sensors, an interpolator and driver stages. Analogue signals of the sensor magnets are detected by the Hall sensors and, after suitable amplification, passed along to the interpolator. By means of a special processing algorithm, the interpolator generates the high-resolution encoder signal.
Lastly, two square wave signals that are phase-shifted by 90 °e, as well as an index signal to display output shaft rotation are available at the outputs.
- Compact modular system and robust housing
- Various resolutions available as standard feature
- Index channel for referencing a rotation of the drive shaft
- Also available as Line Driver version
- Standardized electronic encoder interface
- Flexible customer-specific modifi cations including custom resolution, direction of rotation, index pulse width and index position are possible
The incremental encoders of the IEH2-4096 and IEH3-4096 series consist of a multi-part magnetic ring, which is attached to the rotor, and an angle sensor. The angle sensor comprises all necessary functions, such as Hall sensors, an interpolator and driver stages. Analog signals of the sensor magnets are detected by the Hall sensors and, after suitable amplification in the incremental encoder, passed along to the interpolator. By means of a special processing algorithm, the interpolator generates the high-resolution encoder signal.
With this, two square wave signals that are phase-shifted by 90°e with up to 4,096 lines per revolution, as well as one additional index signal are available at the incremental encoder outputs. The encoder is integrated in the motors of the SR series and lengthens these by just 1.4 mm.
- Extremely compact
- High resolution of up to 16,384 edges per revolution (corresponds to a 0,022° angle resolution)
- No pull-up resistors are necessary at the outputs because there are no open collector outputs
- Symmetric switching edges, CMOS and TTL-compatible
- Different resolutions, according to encoder type, from 16 to 4,096 lines, are available for standard delivery
- High signal quality