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ControlNet NetChecker
Rockwell Automation Publication 1788-UM001B-EN-P - August 2012
Product Overview
The 1788-CNCHKR NetChecker is a hand-held tool for testing active ControlNet networks. It
is pocket-sized and battery-powered for field use. The NetChecker helps commissioning and
troubleshooting ControlNet installations by verifying signals on the ControlNet cabling. For
example, installers are able to find shorts and termination faults by using the NetChecker. The
tool is designed to evaluate the quality of the signal on the coaxial medium. It does not interpret
the content of messages, except for the addresses of the nodes issuing messages.
The NetChecker checks several electrical characteristics of the signal:
•
Level of distortion
•
Noise or signal reflections
•
Rising and falling edges
•
Minimum message duration
•
Minimum between-message duration
•
Peak-to-peak amplitude
•
Violations to Manchester signal encoding
An evaluation of the signal quality is made using a combination of criteria on all the above
characteristics. Most of the criteria used are fixed by design and therefore cannot be modified by
the user. The input signal from the network is converted to a 2-level digital signal using a voltage
reference. This voltage reference (or threshold) is the only criteria that can be modified by the
user by means of a slide switch (SW3). The results of the signal analysis are displayed by bi-color
status indicators.
Additional features include a Node Finder and an oscilloscope output. The Node Finder detects
the presence of a given node on the network. The user enters the node address on thumbwheel
switches. The oscilloscope output provides a trigger and an electrically isolated network signal
for displaying messages from a specified node on an oscilloscope.
The NetChecker is designed to be connected to a network via either a standard tap or the
provided BNC T and cable. The NetChecker is a passive instrument. It does not send any signal
on the network under test.
