Technical Information - OHAUS CKW Serie Instrucciones De Instalación Y Operación

CKW Serial Interface Option Kit
INTRODUCTION
These instructions contain information on the installation, setup, and operation of
the RS485/422 Serial Interface Option Kit used with Ohaus CKW Series Indicators
and Scales. The kit includes all necessary components to modify the CKW-55
Indicator to communicate to external equipment using RS485/422 formats.
Each kit contains a PC board, 4 mounting screws, 2 interconnecting cables and
this instruction manual.
APPLICATIONS
The RS485/422 Serial Interface provides a wider flexibility over basic RS232 serial
communication systems. Typical uses include creation of multiple scale systems
and networks, operation of long distance point-to-point serial communication.
Other benefits include:
• Communication and control of multiple scales using a single cable system.
• Communications requiring long cable runs, (up to 4000 feet, 1200 meters).
• Operation in environments that are prone to high electrical noise.
• Multi-drop and Multi-point system connection capability.

TECHNICAL INFORMATION

Operating Standard
The CKW RS485/422 Serial Interface follows the EIA-485 Industry Standard.
Interface Cables
For RS485/422 systems, high quality, twisted pair cables should be used for all
but the shortest cable distances. Cable impedance should be close to 120 ohms.
Category 5 cables with an impedance of 100 ohms are generally acceptable.
The CKW RS485/422 option supports 4-wire duplex or 2-wire half duplex
operation. Examples of these configurations are shown in Appendix A.
Termination Resistance
The CKW RS485/422 Option can provide a termination resistance if required.
Larger RS485 systems may require a termination resistance to improve the
reliability of the cable system. Adding a termination resistance helps absorb
excess signal energy that might otherwise reflect back into the system and cause
undesirable noise. When used, a termination resistance is usually placed on the
last RS485 device located at the end of a cable system.
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