Rockwell Automation 1788-CNCHKR ControlNet NetChecker User Manual - Manual (Page 7)

ControlNet NetChecker 7
Rockwell Automation Publication 1788-UM001B-EN-P - August 2012
TRAFFIC Status Indicator
This bi-color status indicator at the top of the instrument has two functions:
• Green (network activity)— When the NetChecker is connected to an active network
and powered on this status indicator will turn green to indicate there is activity on the
network. Only messages in which a Start Delimiter is detected in the header (and thus
are considered valid) can cause this status indicator to turn green.
• Red (low battery)— If the batteries are low the status indicator will turn red, whether or
not the tool is connected to a network.
Modes of Network Analysis
The NetChecker offers two modes of analysis to evaluate a network:
• Diagnostic mode —Provides a global network evaluation. It is selected when slide
switch SW3 is in the L, M, or H position.
• Bargraph mode —Provides a quick view of the signal level on the network, either global
(from all nodes) or from a selected node. It is selected when slide switch SW3 is in its
rightmost position.
Diagnostic Mode
In Diagnostic mode positions L, M, and H on slide switch SW3 select one of three fixed voltage
references (or thresholds) used by the NetChecker to convert the analog input signal to a binary
signal.
The L (low) reference voltage setting is the most sensitive to input signal or noise. When the L
position is selected any input signal exceeding +/-300mV will be converted to a logical “1” and
processed by the NetChecker. All input signals between +300mV and -300mV will be converted
to a logical “0” and ignored. Note that this sensitivity range is deliberately set above the absolute
minimum peak-to-peak voltage required by the ControlNet specification (510mVpp).
The M (medium) and H (high) positions provide higher voltage references and less sensitivity as
shown in the table above.
Table 2 - Threshold Settings
Sensitivity to Noise SW3 Position Reference Voltage (mV) Volts (peak-to-peak)
Most sensitive L 300 0.6
Moderately sensitive M 450 0.9
Least sensitive H 600 1.2