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     ControlNet NetChecker

Rockwell Automation Publication 1788-UM001B-EN-P - August 2012

Typical Waveforms

Example of Waveform Seen When Network Is Improperly Terminated

Good Signal

Small Amount of

Reflection

Remote

Station

6.000 V/D
100 nS/D

2.000 V/D
500 ns/DIV

Содержание Allen-Bradley 1788-CNCHKR

Страница 1: ... 1788 CNCHKR Topic Page Important User Information 2 European Communities EC Directive Compliance 3 Additional Resources 3 Product Overview 4 Diagnostic Mode 7 Bargraph Mode 9 Operation 11 Reporting Examples 17 Additional Tips 20 Waveform Examples 21 ...

Страница 2: ...rinstallation RockwellAutomation Inc cannotassumeresponsibilityorliabilityforactual use based on the examples and diagrams No patent liability is assumed by RockwellAutomation Inc with respect to use of information circuits equipment or software described in this manual Reproduction of the contents of this manual in whole or in part without written permission of Rockwell Automation Inc is prohibit...

Страница 3: ...ent EN 50082 2 EMC Generic Immunity Standard Part 2 Industrial Environment This product is intended for use in an industrial environment AdditionalResources These documents contain additional information concerning related products from Rockwell Automation You can view or download publications at http www rockwellautomation com literature To order paper copies of technical documentation contact yo...

Страница 4: ...o 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 m...

Страница 5: ... On Line Diagnostic 2 3 4 5 6 7 L M H Threshold INPUT Rockwell Automation Push ON Buzzer Ext 5VDC 0 25A Power Max Min 0 7 Signal x1 4 GND Trigger Output to Scope Node Finder Power Switch OFF ON Push ON Bargraph Pass Fail Slow Edges Illegal Framing Poor Signal Quality Allen Bradley ControlNetTM NetChecker BNC Connector SW3 SW2 SW1 on the side Input Jack ...

Страница 6: ... indicators numbered 1 to 7 are dual function for Diagnostic or Bargraph modes Status indicators named TRAFFIC also indicates a low battery condition Thumbwheel switches 2 digit decimal switches for entering the address of the Node to find 0 to99 DC jack External DC power from AC adapter nominal 5V DC max 5 5V 0 25A Jack should have 3 5 mm external diameter and 1 35 mm internal diameter Oscillosco...

Страница 7: ... 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 DiagnosticMode 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 sensiti...

Страница 8: ...ecker may interpret that there are unexpected violations although the message was generated correctly by the originator node Illegal Framing status indicator Blinks red when erratic message detection occurs The NetChecker verifies the duration of messages and generates a fault if any message is shorter than 7 bytes NULL message length In addition the time gap between messages must not be less than...

Страница 9: ...er also provides a synchronization signal for viewing the messages from a given node with a digital storage oscilloscope DSO This signal trigger is provided on the 3 pin connector on the left side of the NetChecker The connector pin labeled Signal delivers the signal from the network via an input transformer with a 1 4 isolation stage The NetChecker ground is provided on the center pin The Trigger...

Страница 10: ...he Node Finder thumbwheels Note that the bargraph indication is the level seen at the point of test so a low or high indication does not necessarily mean that the node itself is faulty If all of the status indicators are off the NetChecker does not detect any signal from a node having the address entered PerformaGlobalSurveyofSignalLevels To perform a global survey of the signal levels of all mess...

Страница 11: ... the NetChecker set power switch SW1 to the Push ON position then press and hold the Push ON button for just the time necessary a few seconds to read the status indicators If you need your hands free set SW1 to the ON position middle so that the NetChecker remains powered on Remember to put SW1 back to the OFF position when you are done UseaWallAdaptertoPowertheNetChecker The NetChecker may also b...

Страница 12: ... taps for testing With a redundant network you can temporarily disconnect one of a node s taps from the network and test from this Recognize however that you are removing a node from the network Test that node later from a different location on the network INPUT Node On Line Push ON Control Net Net Checker TRAFFIC L M 7 6 5 4 3 2 1 Min Max H Low Battery Bargraph Diagnostic Signal x1 4 GND Trigger ...

Страница 13: ...can indicate that there is a problem on the tested network but it cannot indicate where the problem originated However it can help to locate intermittent defects as described in Additional Tips on page 20 Keep in mind that the source of a problem may be far away from the point of analysis NetworkDiagnostics This section describes procedures for evaluating the quality of the ControlNet network Howt...

Страница 14: ...etting of SW3 When analyzing a network the NetChecker indication may differ from one point of test to another A network may be acceptable if the NetChecker reports faults with a low or even medium threshold setting at some points but a network that exhibits faults everywhere should be inspected Try to evaluate residual problems using the Node Finder and an oscilloscope to ensure that the signals m...

Страница 15: ...mismatches Poor Signal Quality may be reported along with Illegal Framing and possibly Slow Edges for all the threshold settings This indicates large impedance mismatches caused by an open trunk cable or a short circuit In such cases the Node Finder may have difficulty detecting the presence of some nodes on the network because of the high amount of distortion In cases where the received signal ha...

Страница 16: ...narios Only Illegal Framing is reported It is not affected by the threshold setting The fault is reported everywhere on the network but the bargraph shows correct signal levels In this case try to identify the node with the Node Finder Check the Node On Line status indicator for each of the known addresses of your network The faulty node is signalled by the Node On Line status indicator turning re...

Страница 17: ...ph shows that the minimum level is correct Slow Edges may also be reported along with Poor Signal Quality and Illegal Framing in the case of strong impedance mismatches on the network causing a high amount of distortion In this situation the threshold setting may influence the recurrence of the faults ReportingExamples The figures below show examples of the reporting by the NetChecker ChecktheSign...

Страница 18: ... Line Diagnostic 2 3 4 5 6 7 L M H Threshold INPUT Rockwell Automation Push ON Buzzer Ext 5VDC 0 25A Power Max Min 0 7 Signal x1 4 GND Trigger Output to Scope Node Finder Power Switch OFF ON Push ON Bargraph Pass Fail Slow Edges Illegal Framing Poor Signal Quality Allen ControlNetTM NetChecker TRAFFIC Low Bat 1 Node On Line Diagnostic 2 3 4 5 6 7 L M H Threshold INPUT Rockwell Automation Push ON B...

Страница 19: ...ale turns red a level of signal greater than 9 5Vpp was detected This may indicate a strong mismatch on the network Check if terminations are present TRAFFIC Low Bat 1 Node On Line Diagnostic 2 3 4 5 6 7 L M H Threshold INPUT Rockwell Automation Push ON Buzzer Ext 5VDC 0 25A Power Max Min 1 2 Signal x1 4 GND Trigger Output to Scope Node Finder Power Switch OFF ON Push ON Bargraph Pass Fail Slow Ed...

Страница 20: ...c mode is a valuable tool to help locate such problems Read the NetChecker while subjecting each trunk connector or tap to a moderate mechanical stress If faults are reported the BNC connector has not been mounted correctly and must be replaced ContinuousNetworkMonitoring To provide continuous monitoring the NetChecker powered by an AC wall adapter can be installed temporarily or permanently on th...

Страница 21: ...aveforms that may be seen on a ControlNet network IdealTransmittedPacketonControlNetNetwork asseenattransmittingnode IdealReceivedPacketonControlNetNetwork asseenatreceivingnode t V V 0V One Bit Time 200nS Tx Off Waveform on Cable 5 Mbps Manchester Encoded Transmit Level 8 2Vpp 1 3V 510mVpp min 40nS max jitter 100nS Receive Mask 0 Volt ...

Страница 22: ...Rockwell Automation Publication 1788 UM001B EN P August 2012 TypicalWaveforms ExampleofWaveformSeenWhenNetworkIsImproperlyTerminated Good Signal Small Amount of Reflection Remote Station 6 000 V D 100 nS D 2 000 V D 500 ns DIV ...

Страница 23: ...resistance of contact in connectors Incorrect network architecture EffectofAttenuationonSignalEdges Excessive attenuation causes loss of signal Poor quality coaxial cable Resistance too high Losses in dielectric Overloaded network Too long trunk segment Excessive number of nodes per segment Impedance mismatches IMPORTANT Each coaxial segment must be terminated with a 1786 TCAP terminator at each e...

Страница 24: ...ial Customer Support number for initial help in getting your product up and running NewProductSatisfactionReturn Rockwell Automation tests all of its products to ensure that they are fully operational when shipped from the manufacturing facility However if your product is not functioning and needs to be returned follow these procedures DocumentationFeedback Your comments will help us serve your do...

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