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Rotary Encoder - absolute and optical with hollow shaft
S21B | S21G | S21P

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.

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  • 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

Absolute encoder models

Characteristics Unit S21B S21G S21P    
Type   absolute, serial absolute, serial absolute, parallel    
Output signal   SSI binary (2 or 3 lines) SI Gray code (2 or 3 lines) Parallel Gray code    
Resolution   8 to 16 bit   8 to 16 bit   13 bit
Output frequency max.   5 MHz clock 5 MHz clock 0.3 MHz per data set    
Output   SSI interface SSI interface TTL amplifier    
Power supply   5 VDC, 45 mA 5 VDC, 45 mA 5 VDC, 60 mA    
Shaft bore max. mm 12.7        
Shaft length min. mm 6.35        
shaft length max. mm 28.58        
axial shaft movement mm ± 0.635 ± 0.635 ± 0.254    
max. speed rpm 10000 max        
Operating temperature °C 0 to 70 0 to 70 -40 to 85    
Storage at °C -40 to 125 -40 to 125 -55 to 100    
Relative humidity % 90 non-condensing        
Shock g 100 (6 ms duration)        
Vibration Hz 10 - 2,000 at 10 g        
Protection class   IP40        

Connections for absolute rotary encoders

Modell Stecker Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15  
S21B, S21G DF11-8DP-2V Signal DATA+ DATA- CLOCK+ CLOCK- 5VDC GND NC NC - - - - - - -  
S21P F1-W15P-HFE Signal GND VDC G12 G11 G10 G9 G8 G7 G6 G5 G4 G3 G2 G1 G0  


S21C BiSS C incremental

S21P Parallel Gray Code

S21B and S21G Binary and Gray Code SSI

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