HBA2 Absolute Blind Hollow Bore Optical Encoder

End of Life (EOL) Notification: The HBA2 is EOL and not recommended for new product development. See PCN 1029 for details or contact US Digital support at support@usdigital.com for more info.
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  • 12 bit single turn absolute encoder
  • Hollow bore design tolerates run-out
  • Programmable zero location
  • Low cost
  • Industrial duty 6805 series bearings
  • Analog output option available
  • Programmable resolution
  • Programmable CW or CCW count direction
  • -25C to 70C operating temperature
  • Two year warranty

The HBA2 is a fully programmable blind hollow bore 12 bit absolute encoder designed to easily mount to any rotating shaft. This single turn absolute encoder provides 12 bit resolution over 360 degrees...

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Product Specifications

Operating Temperature -25 to 70 C
Storage Temperature -40 to 100 C
Humidity, Non-condensing 0 to 95 %
Vibration (5Hz to 2kHz) 20 G
Shock, 11 mSec 50 G
Electrostatic Discharge, Human Body Model ± 4 kV
Max. Acceleration 100000 rad/sec^2
Max. Shaft Speed 6000 rpm
Max. Shaft Torque 0.70 oz-in typical
Max. Shaft Loading 5 lb.
Weight 11.5 oz.
Max. Shaft Total Indicated Runout 0.010 in.
Max. Shaft Axial Play ± 0.030 in.
Max. Shaft Insertion Depth 0.85 in.
Moment of Inertia 3.7 x 10^-3 oz-in-s^2
Technical Bulletin TB1001 - Shaft and Bore Tolerances Download
  • Specifications apply over entire operating temperature range.
  • Typical values are specified at Vcc = 12V and 25C.
Supply Voltage 5.5 12 16 V
Supply Current



Analog Output Impedance 950 1000 1050 Ohms
Zero Scale Analog Voltage 0 0.0005 0.003 V
Full Scale Analog Voltage 4.079 4.095 4.111 V
Output Noise (Analog version)   10   mVrms
Differential Nonlinearity -1.0   1.0 LSB
Absolute Accuracy (SEI interface version)   0.18 0.25 Degrees
Angle tracking speed
  Single-turn mode
  Multi-turn mode
 Position Update Rate (1)      7 msec.

(1) The internal microcontroller takes a snapshot of the disk every 7 msec. and stores the position in memory. It responds immediately to a "report position request" by sending this value which is always the most current position.


The analog version of the HBA2 has a 12-bit DAC on the output which feeds to 2 lines that are otherwise used for the BUSY handshaking pair. This DAC has a full range of 0 to 4.095 volts which is 1 milli-volt per bit. The value which the internal microcontroller sends to that DAC is the same as the digital value that it sends to the host. Since the resolution (which represents the number of codes per revolution) is field programmable, the range of the DAC will also follow that setup. Our default resolution is 3600 codes per revolution which yields 1 count per tenth of a degree. This makes the DAC output equal to 1 milli-volt per tenth of a degree or 0 to 3.599 volts. When the DAC needs to have the full range to 4.095 volts, the single turn resolution should be set to 4096. This is easily done with the available software which runs on a PC.  Cable CA-MD6A-SS-MD6-6FT and either the SEI-USB or the AD2B adapter are needed to interface the HBA2 analog version to a USB port or RS-232 serial COM port.

Please Note: The BUSY handshaking lines are replaced by the analog output option. This means that only one device will be able to be connected to the SEI bus when using the analog output option.

1 Ground
2 Busy+
3 Busy-
4 Power
5 DataL
6 DataH
Title Date Description Download
EOL HBA2 - PCN 1029 6/17/2013 This PCN is a formal notification that US Digital is discontinuing the HBA2. Download

Product Description

The HBA2 is a fully programmable blind hollow bore 12 bit absolute encoder designed to easily mount to any rotating shaft. This single turn absolute encoder provides 12 bit resolution over 360 degrees of rotation in a serial output format. The HBA2 communicates via US Digital's SEI (Serial Encoder Interface) bus. The SEI bus is a simple convenient network of devices interfacing to a RS232 serial port. This bus can support 1 to 15 devices on a single 6-wire cable with lengths up to 1000 feet. 

The HBA2 is a bearing style encoder which features a hollow bore that may be ordered in sizes to accept shaft diameters of 0.250" up to 0.750". The Absolute encoder slips over the shaft and is locked in place with two 6-32 set screws. A flexible anti-rotation tether provides single point mounting for bolt circles ranging from 2.50" up to 5.00" in diameter and compensates for shaft run out of up to ±0.03" axial and ±0.01" radial.

SEI Explorer software is provided along with the HBA2 absolute encoder to allow access to the programmable features of the encoder. The SEI bus connects to a serial port via US Digital's AD2B or SEI-USB interface adapters. The AD2-B adapter is powered by a wall mount 12VDC power supply and also provides power to the HBA2 encoder by means of the interconnection cable. The SEI-USB can source power from the USB cable, or accept power from a wall mount power supply.

The HBA2 absolute encoder may be used in many stand alone applications that do not require a PC interface. For these applications we provide detailed communications protocols for this product (see the SEI Absolute Encoder Communications Protocol data sheet).

An analog output option is available for the HBA2 hollow bore absolute encoder. It provides a 12 bit analog output voltage proportional to angular position over 360 degrees. The Analog output option is fully functional with the SEI bus, but is limited to one device on the bus instead of multiple units on the bus.

Product Notes
  • Cables and connectors are not included and must be ordered separately.
  • US Digital warrants its products against defects in materials and workmanship for two years. See complete warranty for details.

Cable/connector assembly not included and must be ordered separately.

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This product is no longer configurable or available for new applications.