US Digital

The HD25A is a rugged absolute encoder designed for heavy duty industrial use. This absolute encoder is a non-contacting optical rotary position sensor which reports the shaft angle within a 360 range. The HD25A can be used for automation, motion control and robotic applications. As opposed to incremental encoders, the HD25A reports the absolute position rather than just the change in position. The HD25A is a true absolute encoder over one revolution, and also has a multi-turn mode. 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 HD25A has 2 separate outputs, one utilizes our digital SEI (Serial Encoder Interface) bus and the other is an analog output. The SEI bus is a simple, quick, convenient network of devices interfacing to a RS232 serial port. The SEI bus supports 1 to 15 devices on a single cable up to 1000 feet long (RS-485 like). The analog output provides an analog voltage proportional to the angular position, with 12-bit resolution.

For access to both the SEI bus and analog signal outputs, the AD7 adapter is recommended. US Digital offers two SEI  to PC 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 HD25A to a PC via our SEI bus. The wall-mount PS-12 power supply furnishes the power for all devices on the SEI bus.

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).

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.

Analog Output:

The HD25A has a 12-bit DAC and 2 dedicated analog output line (Analog+, Analog-). This DAC has a full range of 0 to 4.095V, which is 1mV 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 CPR which yields 1 count per tenth of a degree. This makes the DAC output equal to 1mV per tenth of a degree or 0 to 3.599V. When the DAC needs to have the full range to 4.095V, the single turn resolution should be set to 4096. This is easily done with the available software which runs on a PC. See referenced documents information on the AD7 HD25A Breakout Box.

Available Options:

• Shaft seal to protect the encoder from liquids. Note that this option adds about 3.5 in-oz. of shaft drag.
• 3/8" diameter shaft with or without flat.

Notice:

In applications where a failure could result in an unacceptable loss, we recommend that your system be designed to include two redundant encoders with the outputs from both continuously compared to make sure that they agree. If there is a discrepancy, the system should be designed to automatically shut down as a fail-safe measure to minimize the risk of damage or danger. This product is not certified for applications where a failure could result in a costly, dangerous, or life threatening situation.