US Digital

A2 Absolute Optical Encoder

Overview

  • Sleeve bushing or ball bearing versions
  • 12-bit accuracy and resolution field programmable from 2 to 4096 codes per revolution (3600 factory default)
  • Full 360 degrees range and position update rate is 250 times per second
  • Low power drain of 18.5 mA max., and 1.5 mA in sleep mode
  • Field programmable parameters such as setting zero position point (free demo software provided)
  • 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

Product Specifications

sei_network.gif

Pin Description
1 Ground
2 Busy+
Analog+
3 Busy-
Analog-
4 Power
5 DataL
6 DataH
ParameterMin.Typ.Max.Units
Supply Voltage (PWR) 5.5 - 16 Volts
Supply Current (Active) - 14 18.5 mA
Supply Current (Sleep) - - 1.5 mA
Analog Output Impedance (Anlg+) 950 1000 1050 Ohms
Zero Scale Analog Voltage 0 .0005 .003 Volts
Full Scale Analog Voltage 4.079 4.095 4.111 Volts
Differential Nonlinearity -1.0 - 1.0 LSB
  • Specifications apply over entire operating temperature range.
  • Typical values are specified at Vcc= 12V and 25C.
Parameter Min. Max. Units
Storage Temperature -40 100 C
Operating Temperature -25 70 C
Humidity (Non-condensing) 0 95 %
Supply Voltage (PWR) 0 16 Volts
DataH, DataL, Busy+, Busy- -14 14 Volts
A2 Electrical tracking (Multi-turn Mode) - 1800 RPM
A2 Electrical Tracking (Single-turn Mode) - 3600 RPM
A2 Position Update Rate* - 4 mSec

* The internal microcontroller takes a snapshot of the disk every 4 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 A2 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 A2 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.

Product Description

The A2 absolute encoder is a non-contacting optical rotary position sensor which reports the shaft angle within a 360 range. As opposed to incremental encoders, the A2 reports the absolute position rather than the change in position. When powered up, it does not require a home cycle, even if the shaft was rotated while the power was off. In multi-turn mode, it tracks the position in a 32-bit counter as long as the power supply is maintained. Internally, an infrared LED flashes through a circular bar code onto a linear array sensor. The microcontroller decodes the image into a unique position. All user programmable parameters such as resolution, origin, direction and mode are permanently stored in an internal EEPROM.

The interface of the A2 utilizes our SEI (Serial Encoder Interface) bus. The SEI bus is a simple, quick, convenient network of devices interfacing to an RS-232 serial port or USB port. The SEI bus supports 1 to 15 devices on a single, 6-wire telephone-type cable up to 1000 feet long (similar to RS-485). 

US Digital offers two SEI interfaces: the AD2B adapter for interface to an RS-232 port and the SEI-USB for interface to a USB port. One of these products is required in order to interface the A2 to a PC via our SEI bus. The wall-mount PS-12 power supply furnishes the power for all devices on the SEI bus.

US Digital provides software free of charge for all products which require software for operation. The software can be used as is or it can serve as an example for creating your own custom application. The absolute encoder software utilizes our SEI Explorer software to configure and communicate with the product from a PC platform.

Our absolute encoders may be used in many stand alone applications that do not require a PC interface. For these applications we provide detailed communications protocols for all of our absolute products (see the SEI Absolute Encoder Communications Protocol page).

An analog voltage output (A-option) is available for the A2.  An A2 with the analog option can stand alone (does not need to connect to a PC), providing an analog voltage (0 to +4.095 volts maximum) that is proportional to the angular position, with 12-bit resolution. A2 encoders with the A-option can still be communicated with on the SEI bus, but only one device can be on the bus at a time instead of up to 15 devices.

Product Notes
  • US Digital warrants its products against defects in materials and workmanship for two years. See complete warranty for details.
Related Documentation

Purchasing

Configure and Purchase

1. Interface


2. Torque



3. Cover


4. Base


5. Housing


Product Part Number
Quantity Price
1 $283.50
10 $252.00
50 $241.50
100 $231.00
Over 100 Call for quote
Quantity
Unit Price

$283.50

Subtotal

$283.50

For your convenience, use the above part number to order via phone 800.736.0194

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