Chapter 1 - Overview
1-1
CHAPTER 1 - OVERVIEW
Allen-Bradley License
Under license from The Allen-Bradley Corporation, Hardy Process
Solutions Inc. has developed a Remote I/O Interface for the HI 2151
Weight Controller. The HI 2151WC is a general purpose industrial and
process weighing instrument for use in a wide variety of applications
including filling, dispensing, batching, and monitoring rate of flow by
weight. The instrument includes numerous features and technologies
including up to eight setpoint relays, 1,000,000 counts of resolution,
Secure Memory Module for backup of critical calibration data, and
WAVERSAVER
®
, the ability to ignore plant and process mechanical
noise to quickly arrive at stable weight readings.
Hardy Process Solutions worked with substantial customer input and
Allen-Bradley to identify that the remote I/O communications network
best matched the needs of system integrators and end users for indus-
trial and process applications. The interface is fast, field proven,
requires minimal wiring, requires no special software drivers, and is
standard on many Allen-Bradley programmable controllers. Setting
each address and baud rate in the instrument, connecting three wires,
and writing some ladder logic is all that is needed to begin communi-
cating weighing parameters to and from an HI 2151WC controller.
Each Hardy HI 2151WC represents a quarter (1/4) rack of discrete I/O
(32 bits in the PLC Output and Input image files) to the scanning PLC
and supports both discrete and block transfers. The PLC continually
exchanges 32 bits of its PLC Input Image Table and 32 bits of its Out-
put Image Table with each 1/4 rack device. In a 1771 I/O Rack, these
bits would normally be transferred from and to discrete input and out-
put modules. For the weight controller, the Output Image bits are used
to send commands to the weight controller and the Input Image bits
return weight data and scale status bits. These actions are referred to as
“discrete writes and “discrete reads”. The user is also able to exchange
blocks of data with a 1/4 rack device via Block Transfer instructions in
the PLC ladder logic program. These commands are referred to as
“block writes” and “block reads”.
The host programmable controller can access all configuration and
weighing parameters in the HI 2151WC, including performing scale
calibration. The HI 2151WC can be used as a local display and key-
board for weighing parameters, or function as a blind controller prop-
erly digitizing the load cell signal and providing responsive setpoint
control.
Using the Remote I/O interface shortens development time and pro-
vides the most functional weighing interface available for your Allen-
Bradley programmable controller. Before starting system design, you
