Feedback Devices

Feedback Devices

Feedback devices are a class of device required for closed loop operation. They provide a signal back to the drive or motion controller to monitor an operation or process and verify that proper operation occurs. In Motion Control applications, there are two primary feedback devices: Resolvers and Encoders.

A resolver is an electromagnetic feedback device which converts angular shaft position into analog signals. These signals can be processed in various ways, such as with an RDC (resolver-to-digital converter) to produce digital position information. There are two basic types of resolvers; transmitter and receiver. A transmitter-type is designed for rotor primary excitation and stator secondary outputs. Position is determined by the ratio of the sine output amplitude to cosine output amplitude. A receiver-type is designed for stator primary excitations and rotor secondary output. Position is determined by the phase shift between the rotor output signal and one of the primary excitation signals.

The most popular type of Feedback Device is the Encoder. An encoder is an electromechanical device for translating linear or rotary displacement into a corresponding series of digital signals or analog output voltage.

Incremental vs. Absolute Encoders View More

Incremental Encoders

A device that generates electrical signals by means of a rotating disk that passes between a light source and photo detectors. Incremental encoders have two output signals, or channels, commonly referred to as channel A and B. The A and B outputs are nominally 90º out of phase with each other and are interpreted by a motion controller to determine position/velocity information. The lead/lag relationship between the A and B channels provides directional information. It is important to understand that each mechanical position is not uniquely defined. When the incremental encoder is powered on, the position of an incremental encoder is not known, since the output signals are not unique to any singular position. Incremental encoders often provide a third output that pulses once per revolution of the disk. This is typically called the Index, or Z-channel, and is commonly used for homing/reference moves.

Absolute Encoders

Absolute encoders have a unique value (voltage, binary count, etc.) for each mechanical position. When an absolute encoder is powered on, the position is known. Absolute encoders most commonly provide digital data in a parallel or serial format to the motion controller which is used to determine position/velocity information. Since they provide absolute position information when powered on they eliminate the need for a homing/reference move in a motion system.

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  1. CS-7514F-51C DC Tachometers Servo-Tek Products
    CS-7514F-51C

    F-Series, Face Mount, 3 V/1000 RPM, 12000 RPM Max Speed

  2. CS-7561F-51C DC Tachometers Servo-Tek Products
    CS-7561F-51C

    F-Series, Face Mount, 3 V/1000 RPM, 12000 RPM Max Speed

  3. SA-7103A-2 DC Tachometers Servo-Tek Products
    SA-7103A-2

    A-Series, Tapped Holes / Face, 7 V/ 1000 RPM, 12000 RPM Max Speed

  4. SA-7125A-2 DC Tachometers Servo-Tek Products
    SA-7125A-2

    A-Series, Tapped Holes / Face, 7 V/ 1000 RPM, 12000 RPM Max Speed

  5. SA-7356F-1 DC Tachometers Servo-Tek Products
    SA-7356F-1

    F-Series, Face Mount, 7 V/1000 RPM, 12000 RPM Max Speed

  6. SA-7388F-1 DC Tachometers Servo-Tek Products
    SA-7388F-1

    F-Series, Face Mount, 7 V/1000 RPM, 12000 RPM Max Speed

  7. SA-740A-2 DC Tachometers Servo-Tek Products
    SA-740A-2

    A-Series, Tapped Holes / Face, 7 V/ 1000 RPM, 12000 RPM Max Speed

  8. SA-740A-7 DC Tachometers Servo-Tek Products
    SA-740A-7

    A-Series, Tapped Holes / Face, 2.6 V/ 1000 RPM, 12000 RPM Max Speed

  9. SA-757A-2 DC Tachometers Servo-Tek Products
    SA-757A-2

    A-Series, Tapped Holes / Face, 7 V/ 1000 RPM, 12000 RPM Max Speed

  10. SB-7356F-1 DC Tachometers Servo-Tek Products
    SB-7356F-1

    F-Series, Flange Mount, 7 V/ 1000 RPM, 12000 RPM Max Speed

  11. SB-740A-2 DC Tachometers Servo-Tek Products
    SB-740A-2

    A-Series, Flange Mount, 7 V/ 1000 RPM, 12000 RPM Max Speed

  12. SB-740A-7 DC Tachometers Servo-Tek Products
    SB-740A-7

    A-Series, Flange Mount, 2.6 V/ 1000 RPM, 12000 RPM Max Speed

  13. SB-7483H-1 DC Tachometers Servo-Tek Products
    SB-7483H-1

    H-Series, Flange, 16 V/ 1000 RPM, 8000 RPM Max Speed

  14. SB-757A-2 DC Tachometers Servo-Tek Products
    SB-757A-2

    A-Series, Flange Mount, 7 V/ 1000 RPM, 12000 RPM Max Speed

  15. SD-7146A-2 DC Tachometers Servo-Tek Products
    SD-7146A-2

    A-Series, Clamp Mount, 7 V/ 1000 RPM, 12000 RPM Max Speed

  16. SD-740A-2 DC Tachometers Servo-Tek Products
    SD-740A-2

    A-Series, Clamp Mount, 7 V/ 1000 RPM, 12000 RPM Max Speed

  17. ST-12970-1 DC Tachometers Servo-Tek Products
    ST-12970-1

    Sealed/Ruggedized DC Tachometers, Tachometer Assembly Mount, 20.8 V/ 1000 RPM, 8000 RPM Max Speed

  18. ST-13212-2 DC Tachometers Servo-Tek Products
    ST-13212-2

    Sealed/Ruggedized DC Tachometers, Tachometer Assembly Mount, 20.8 V/ 1000 RPM, 8000 RPM Max Speed

  19. ST-7336A-2 DC Tachometers Servo-Tek Products
    ST-7336A-2

    Sealed/Ruggedized DC Tachometers, Tapped Holes / Face, 7 V/ 1000 RPM, 12000 RPM Max Speed

  20. ST-7337A-2 DC Tachometers Servo-Tek Products
    ST-7337A-2

    Sealed/Ruggedized DC Tachometers, Tapped Holes / Face, 7 V/ 1000 RPM, 12000 RPM Max Speed

  21. ST-7337A-2N DC Tachometers Servo-Tek Products
    ST-7337A-2N

    Sealed/Ruggedized DC Tachometers, Tapped Holes / Face, 7 V/ 1000 RPM, 12000 RPM Max Speed

21 Items

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