Hardy HI 2151/30WC Single-Scale Controller - Manual (Page 8)

Chapter 1 - Overview
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CHAPTER 1 - OVERVIEW
Allen-Bradley License Under license from The Allen-Bradley Corporation, Hardy Instruments
Inc. has developed a Remote I/O Interface for the HI 2151 Weight Con-
troller. 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 Instruments 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 industrial
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 communicating weigh-
ing parameters to and from an HI 2151WC controller.
Each Hardy Instruments’ 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 Output 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 output 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