Rockwell Automation Allen-Bradley 842D, Руководство пользователя

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Chapter
1
Overview
Chapter Objectives
Chapter 1 provides an overview of your 842D DeviceNet absolute
encoder. In this chapter, you will read about the following:
• Function of the 842D encoder.
• Features of the 842D encoder.
• Steps for setting up the encoder.
• Required tools and equipment.
Overview of the Encoder
The 842D absolute multi-turn encoder provides a total resolution of
26 bits. The single-turn position value is transmitted with 13 bits. The
number of multi-turn revolutions is 13 bits. Revolutions are counted
by the use of a gear mechanism. The bus interface is located in the
encoder and is configured as a DeviceNet slave according to
DeviceNet specification, release 2.0.
Features of the Encoder
The DeviceNet network is an open, global industry-standard
communication network designed to provide an interface through a
single cable from a programmable controller directly to “smart”
devices such as sensors, push buttons, motor starters, operator
interfaces and drives.
The 842D DeviceNet encoder connects directly to the a DeviceNet
network without the need for additional adapters. Features of the
842D include:
• 26-bit absolute multi-turn operation (8192 steps per revolution x
8192 revolutions) without batteries
• Supports Polling, Cyclic, Change of State (COS) and Bit Strobed
I/O messaging
• Transmission rate up to 500 kBaud.
• Programmable functions
– Electronic alignment (PRESET or Number-SET). Electronic
alignment may be carried out via DeviceNet or via a push-
button in the bus connector of the 842D.
– Clockwise or Counterclockwise (CW/CCW) counting
direction