Topline picture ACHSTRON

Rotary encoder - analog and optical with hollow shaft

The S21 is a cost-effective, optical rotary encoder with a hollow shaft. It is easy to install and achieves a high data rate and resolution. The compact device has its own bearing system and a high-quality, fiberglass-reinforced plastic housing. It therefore achieves protection class IP40. The S21 offers significant performance advantages in applications that would otherwise be limited when using traditional and modular encoder solutions.

A flexible mounting bracket enables a wide range of applications. It tolerates greater shaft end mounting tolerances than other modular encoder systems.

This encoder series is able to provide different output signals: incremental or digital data formats (also with commutation signal) or analog signals (1 Vpp). The incremental versions offer higher resolutions of over 2 million pulses per revolution.

As an alternative to the conventional digital and analog encoder signals, the absolute encoder of this series should be mentioned. The new encoder with 16-bit binary or gray code offers a high number of measuring steps per revolution. A low position error enables smooth drive behavior and remarkable positioning accuracy. High bandwidth and noise immunity ensure excellent speed, stability and control performance in industrial environments.

The S21 also supports the BiSS C protocol for incremental and absolute versions. This fast serial protocol is ideal for dynamic axes that require high acceleration, smooth speed control, excellent bidirectional repeatability and high positioning accuracy. In addition, this encoder is easy to program and configure. In addition, the mechanical dimensions are the same for all variants, which simplifies replacement and design in general.

We are guaranteed to find the right encoder for you - free of charge & without obligation

Enquire now


  • Icon MerkmalCompact mechanical dimensions (53.34 mm outer diameter and 31.12 mm high) for easier system integration
  • Icon MerkmalRobust bearings with industrial ball bearings enable a shaft speed of up to 10,000 rpm
  • Icon MerkmalSimplified direct mount design
  • Icon MerkmalSoftware configurable resolution
  • Icon MerkmalCircuit protection: short circuit, reverse polarity, transient voltage suppression
  • Icon MerkmalASIC-based design for excellent customization and reliability
  • Icon MerkmalFast serial data communication BiSS C via RS-485 differential driver pair
  • Icon MerkmalHigh noise immunity
  • Icon MerkmalRoHS compliant


  • Icon ZahnradWide range of lines and pulses: up to 4096 incremental lines, over 2 million pulses
  • Icon ZahnradRange of shaft diameters: up to 12.7 mm
  • Icon Zahnrad4, 6, 8, 10, & 12-pole commutation tracks, single-ended TTL
  • Icon ZahnradAbsolute position data formats Gray code or binary
  • Icon ZahnradAbsolute position value from 8- to 16-bit SSI output with user clock input pulse
  • Icon ZahnradFast serial SSI communication via 2-wire or 3-wire RS-485
  • Icon ZahnradAbsolute position value on 13-bit parallel output per user connection
  • Icon ZahnradCustomized cable and/or connector

Models of analog rotary encoders

Characteristics Unit S21A
Type   analog
Output signal   1 Vpp sin/cos
Resolution   1,000, 1,024 and 4,096
Output frequency max.   125 kHz
Output   analog
Power supply   5 VDC, 40mA
Shaft bore max. mm 12.7
Shaft length min. mm 6.35
shaft length max. mm 28.58
Axial shaft movement mm ± 0.635
max. speed rpm 10,000
Operating temperature °C -40 to 85
Storage at °C -55 to 125
Relative humidity % 90 non-condensing
Shock g 100 (6 ms duration)
Vibration Hz 10 - 2,000 at 10 g
Protection class   IP40

Digital encoder connections

Model Connector Pin 1 2 3 4 5 6 7 8


Output waveform

Signal shapes clockwise and seen from the end of the encoder shaft

We are guaranteed to find the right encoder for you - free of charge & without obligation

Enquire now

To top