Absolute rotary encoder | Optical | A2

  • Sleeve bushing or ball bearing versions
  • 12-bit resolution and resolution field programmable from 2 to 4096 codes per revolution (3600 factory default)
  • Full 360 degrees range, 7 msec update time
  • Low power drain of 18.5 mA max., and 2.5 mA in sleep mode
  • Field programmable parameters such as setting zero position point (demo software available for download below)
  • EEPROM stores downloadable parameters
  • 9600 baud default data rate adjustable up to 115K baud
  • 12-bit analog voltage output option (0 to +3.599 volts factory default setting. Field programmable up to 0 to +4.095 volts)
  • Multi-turn mode (note: power must be maintained to prevent reset to zero)
  • -25 to 70 degrees C. operating temperature
Manufacturer:US Digital


The A2 optical encoder is a 12 bit absolute rotary encoder which reports a shaft angle within a single 360 degree rotation of a shaft. Unlike incremental, sometimes called relative, style encoders the A2 provides true (absolute) shaft position eliminating the need for a home or zero cycle after a supply voltage power cycle. The A2 communicates over a RS 485 style serial bus utilizing US Digital's SEI (Serial Encoder Interface) which allows for simple, quick and convenient networking of multiple SEI devices on a single network. PLCs, motion controllers and computers can also reside on the SEI bus as well by use of US Digital's SEI to USB interface device. For complete information about the SEI bus please refer to the SEI Communications Protocol webpage.

The A2 is also available with an optional analog output. The analog output option provides a maximum voltage range of 0 to 4.095 volts with 12 bit resolution. The output voltage can be scaled by simple SEI commands to provide user defined voltage ranges. From the factory the analog output voltage is set to 0 to 3.599 VDC range. Please note that with the A2 analog output option only one device may reside on a SEI bus.

Attribute NameAttribute Value
Documentation from Manufacturer
Output Signal Type
Measuring Principle
Resolution Singleturn (bit)
Resolution Multiturn (bit)
SEI Bus, Analog
Housing Diameter (mm)
Shaft Type
Not Specified
Shaft Diameter (mm)
Not Specified
Revolutions - max. (rpm)
10000, 100
Protection Rating Housing
Not specified
Connector, Cable



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