1788-UM001A-US-P, ControlNet NetChecker User Manual
Contents
1. Note that there area number of violations to the Manchester encoding in the ControlNet frame in Start and End Delimiters The NetChecker can detect if there are fewer or more violations than expected In the case of very large distortion of the signal the NetChecker may interpret that there are unexpected violations although the message was generated correctly by the originator node The Illegal Framing LED 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 6 bytes These errors are generally caused by high noise level or signal reflection at the end of the messages or during the time gap between messages These faults are the result of large impedance mismatches on the network This fault detection is dependent on the threshold settings L M and H on SW3 e The Slow Edges LED blinks red when the NetChecker has identified a weak signal with poor rise fall times This may result from high signal attenuation caused by bad coaxial cable excessive cable length or an overloaded network This fault detection is not dependent on the threshold settings on SW3 e The Node On Line LED turns green if a node having the address entered in the Node Finder is detected on the network and the signal received from it is good The LED will turn red or appear y2. ControlNet NetChecker 1788 CNCHKR TRAFFIC Low Bat Output to Scope Diagnostic Bargraph O Signal x1 4 m GND OTrigger Power Switch m OFF O ON O Push ON Slow Edges Node Finder Illegal Framing E D Poor Signal Quality u E Pass Fail Buzzer won ControlNet NetChecker Rockwell Allen Bradley Automation User Manual Rockwell Automation Throughout this manual we use notes to make you aware of safety considerations ATTENTION Identifies information about practices or circumstances that can lead to personal injury or death property damage or economic loss Attention statements help you to e identify a hazard e avoid a hazard o recognize the consequences IMPORTANT Identifies information that is critical for successful application and understanding of the product ControlNet is a trademark of ControlNet International Ltd NetChecker is a trademark of Rockwell Automation European Communities EC Directive Compliance If this product has the CE mark itis approved for installation within the European Union and EEA regions and has been designed and tested to meet the following directive EMC Directive This product is tested to meet the Council Directive 89 336 EC Electromagnetic Compatibility EMC by applying the following standards in whole or in part documented in a technical construction file e EN 50081 2 EMC Ge
3. 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 Publication 1788 UM001A US P November 1999 SW1 on the side BNC Connector TRAFFIC INPUT Output to Scope Diagnostic Bargraph LMH O Signal x1 4 GND SW3 OTrigger Power Switch m OFF o ON o Push ON Node Finder n p ut E E 0 Poor Signal Quality E E Buzzer On ControlNet NetChecker Rockwell Allen Bradley Automation LEFT 1788 CNCHKR ControlNet RIGHT NETCHECKER Publication 1788 UM001A US P November 1999 NetChecker Specifications Dimensions Weight with batteries Environmental Slide Switch SW1 Push Switch SW2 Slide Switch SW3 BNC Connector Display Thumbwheel Switches DC Jack Oscilloscope Connector Buzzer Batteries Battery Life Accessories 152 x 83 x 33 5 mm BNC connector not included 164 x 83 33 5 mm BNC connector included 250 grams 8 18 02 Operating Temperature 0 to 50 C Storage Temperature 40 to 85 C 3 position power switch e OFF disconnects the batteries e ON turns on the tool permanently e Push ON provides momentary power Momentary switch to turn on the instrument when SW1 is in the Push ON position 4 position function switch e Positions
4. 300 0 6 Moderately Sensitive OO M 450 0 9 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 LED Functions When slide switch SW3 is in the Diagnostic left area of the front panel the LEDs have the following functions e The Pass Fail LED indicates the overall quality of the signal on the coaxial cable Green when the input signal is clean this LED will turn progressively red if one or mote of the criteria of quality are violated e The Poor Signal Quality LED blinks red when the message signal is distorted and or when the between messages gap is polluted by noise so that the NetChecker is uncertain if the signal received is a valid message or noise Distortion and noise are generally the result of reflections of signal on the cable caused by impedance mismatches The Poor Signal Quality fault detection is dependent on the threshold settings L M and H on SW3 Publication 1788 UM001A US P November 1999
5. be terminated with a 1786 TCAP terminator at each end Publication 1788 UM001A US P November 1999 A 4 Example Waveforms Effect of Attenuation on Signal Edges e excessive attenuation causes losses of signal poor quality coaxial cable e resistance too high e losses in dielectric overloaded network too long trunk segment e excessive number of nodes per segment impedance mismatches Publication 1788 UM001A US P November 1999 E Reach us now at www rockwellautomation com Wherever you need us Rockwell Automation brings together leading brands in industrial automation including Allen Bradley controls Reliance Electric power transmission products Dodge mechanical power transmission components and Rockwell Software Rockwell Automation s unique flexible approach to helping customers achieve a competitive advantage is supported by thousands of authorized partners distributors and system integrators around the world Americas Headquarters 1201 South Second Street Milwaukee WI 53204 USA Tel 1 414 382 2000 Fax 1 414 382 4444 kuv European Headquarters SA NV avenue Herrmann Debroux 46 1160 Brussels Belgium Tel 32 2 663 06 00 Fax 32 2 663 06 40 Roc ell Asia Pacific Headquarters 27 F Citicorp Centre 18 Whitfield Road Causeway Bay Hong Kong Tel 852 2887 4788 Fax 852 2508 1846 Automation Publication 1788 UMO001A US P November 1999 PN 957236 84 1999 Rockwell International Corp
6. for viewing the messages from a given node with a digital storage oscilloscope DSO This sional 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 signal rises at the end of the transmission of the originator address MacID if the address matches the number on the thumbwheels set the oscilloscope trigger to rising edge We recommend fastening small pieces of solid copper wire 1 inch long 18 22AWG to the terminal block for attachment of the oscilloscope s probes preferably high impedance 10 1 probes Also remember that the peak to peak voltage on the Signal pin is one fourth the peak to peak voltage on the network Bargraph Mode When slide switch SW3 is in its rightmost position the Bargraph mode is enabled and LEDs 1 to 7 function as a maximum minimum signal level indicator This indicator displays the level of the signal from the node selected by the Node Finder When the Node Finder is set to 00 it provides a global view of the signal level maximum and minimum of all the messages seen on the network Publication 1788 UM001A US P November 1999 In Bargraph mode the Poor Signal Quality and Illegal Framing detections are performed with the threshold defaulted to M Medium If Poor Signal Quality or I
7. L M H select the Diagnostic Mode and Low Medium and High Thresholds e The rightmost position selects the Bargraph Mode Signal input Connects to the network trunk cable via a standard tap or the provided cable and BNC T The NetChecker is electrically isolated from the network by a transformer 8 bi color Red Green LEDs e LEDs numbered 1 to 7 are dual function for Diagnostic or Bargraph Modes e LED named TRAFFIC also indicates Low Battery condition 2 digit decimal switches for entering the address of the Node to find 0 to 99 External DC power from AC adapter nominal 5VDC max 5 5V 0 25A Jack should have 3 5mm external diameter and 1 35mm internal diameter 3 pin Phoenix connector with Network Ground and Trigger Signals Piezo Buzzer provides an audible indication of detected faults 2 alkaline batteries 1 5V AA LR6 size located in the battery compartment on the back of the tool Batteries are provided uninstalled with the tool A phillips head screwdriver is required to install or replace the batteries 6 hours continuous use 3 pin plug connector to fit in the Oscilloscope Output BNC T connector BNC male to BNC female coaxial cable 1 meter long User Manual 1788 UM001A US P Publication 1788 UM001A US P November 1999 NetChecker Specifications Agency Certification e EN 55011 Radiated Emission Class A When product or e ENV 50204 Radiated immunity from digital radio packagi
8. To provide continuous monitoring the NetChecker powered by an AC wall adapter can be installed temporarily or permanently on the network The NetChecker will signal immediately any degradation of the signal quality at the media level even if the network is still performing correctly The NetChecker should be set in Diagnostic mode Publication 1788 UM001A US P November 1999 20 Publication 1788 UM001A US P November 1999 Appendix A Example Waveforms This Appendix shows examples of the types of waveforms that may be seen on a ControlNet network Ideal Transmitted Packet on ControlNet as seen at transmitting node 5 Mbps Manchester Encoded Transmit Level 8 2 Vpp 1 3V V hpecsasss One Bit Time 200nS_ Waveform on Cable Publication 1788 UM001A US P November 1999 A 2 Example Waveforms Ideal Received Packet on ControlNet as seen at receiving node p 100nS 40nS max jitter Receive Mask Typical Waveforms Good Signal Small Amount of Reflection Remote Station Publication 1788 UM001A US P November 1999 Example Waveforms A 3 Example of Waveform Seen When Network is Improperly Terminated e impedance mismatches cause reflections on the media network not correctly terminated impedance of coaxial cable not equal to 75Q high resistance of contact in connectors incorrect network architecture IMPORTANT Remember Each coaxial segment must
9. ellow rapidly flashing red and green if the messages received from this node exhibit one or more of the faults signaled by the fault LEDs Note that when this LED 1s red it generally does not mean that the node itself is bad but rather that the signal received by the NetChecker from this node is affected by a problem on the network An impedance mismatch may cause some nodes to be received as good Node On Line LED green while others are received as bad Node On Line LED red Testing at another point on the network will show that nodes that were received as bad are now received as good or vice versa If a Node really is bad it will appear bad everywhere on the network The NetChecker can only rely on the signal it receives at one point on the network That is why a network should always be checked at several points Publication 1788 UM001A US P November 1999 Buzzer The Buzzer sounds any time a fault is detected Node Finder and Oscilloscope Output The address Mac ID of the message originator is the only information from a message that can be decoded by the NetChecker This address is compared to the address entered on the two thumbwheels the possible node addresses range from 01 to 99 Depending on the setting of SW3 the comparator either activates the Node On Line LED Diagnostic mode or enables the display of the level of signal recetved from the node Bargraph mode The Node Finder also provides a synchronization signal
10. esistance at the contact points of the BNC connectors on the trunk cable may add abnormal signal attenuation A small amount of Slow Edges can be tolerated on long networks provided that the Bargraph 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 Publication 1788 UM001A US P November 1999 17 Examples The figures below show examples of the reporting by the NetChecker Checking the Signal Level Using the Threshold Setting In the example at left the NetChecker reports no fault at the highest sensitivity Low Threshold The network is OK at the point of test The LED Node On Line is green because there is a node transmitting at address 07 The example at right shows faults reported at High Threshold Generally this indicates a high level of reflections on the network the network may not be correctly terminated is accidentally open or shorted there is bad contact in a BNC connector etc The LED Node On Line is off because there is no node at address 11 Low Threshold Setting High Threshold Setting Highest Sensitivity Level Lowest Sensitivity Level TRAFFIC TRAFFIC INPUT INPUT Low Bat Low Bat Output to Scope Output to Scope Diagnostic Bargrap
11. h O Signal 1 4 O Signal x14 LM R __ GND GND M N OTrigger OTrigger Power Switch Power Switch Node On Line 7 Max age Green ae o ON O ON O Push ON O Push ON Blinking Red Node Finder Node Finder Green Red Push ON Push ON uzzer po Ext Buzzer n En ue am o BT ControNet NetChecker ControNet NetChecker Rockwell Rockwell Allen Bradley Automation Allen Bradley Automation Publication 1788 UM001A US P November 1999 18 Checking the Signal Level Using the Bargraph Set slide switch SW3 to its Bargraph rightmost position and set the Node Finder to zero to get a global level indication Press the ON switch and make sute that the TRAFFIC LED is green Generally the Bargraph displays two green LEDs indicating the maximum and the minimum level of signal seen at the point of test on the network Normally these should be in the range of LEDs 2 to 6 TRAFFIC INPUT Low Bat Diagnostic Bargraph L MH Output to Scope O Signal x1 4 GND Threshold OTrigger Node On Line 7 Max Power Switch OFF O ON O Push ON Node Finder Push ON Buzzer Ext w e ControNet NetChecker Rockwell Allen Bradley Automation Bargraph Global Mode Publication 1788 UM001A US P November 1999 TRAFFIC INPUT Low Bat Diagnostic Bargraph Output to Scope L MH Threshold OTrigger Node On Line 7 Max Power Switch OFF O ON O Pu
12. in which repeaters are used the level read on the Bargraph for nodes that are behind a repeater 1e on another trunk cable than the one being tested is the level of signal from the repeater Performing a Global Survey of Signal Levels To perform a global survey of the signal levels of all messages on a network set SW3 to its rightmost position and set the Node Finder thumbwheels to 00 zero The NetChecker will display two green LEDs indicating the strongest and the weakest levels encountered on the network The maximum and the minimum levels indicated remain latched until NetChecker power is cycled Oscilloscope Output in Bargraph Mode In Node Signal Level Bargraph mode the Oscilloscope Output is operational in the same way as in Diagnostic mode In Global Bargraph mode however no trigger signal is provided since there can be no ControlNet node at address 00 Publication 1788 UM001A US P November 1999 10 Operation Installing the Batteries Use a Phillips head screwdriver to remove the two screws from the battery cover on the back of the NetChecker Install the two 1 5V AA batteries supplied as indicated in the compartment Batteries installed incorrectly may damage the instrument Use only alkaline batteries for replacement Conserving Battery Power To conserve battery power when using the NetChecker set power switch SW 1 to the Push ON position then press and hold the Push ON button for just the time nece
13. ith network cabling and that its D gt sensitivity is greater than required by the ControlNet specification Publication 1788 UM001A US P November 1999 Poor Signal Quality Poor Signal Quality has the following indications LED State TRAFFIC Green Slow Edges May also be blinking Red legal Framing May also be blinking Red Poor Signal Quality Blinking Red Pass Fail Yellow or Red Buzzer Sounds A blinking Poor Signal Quality LED often indicates that signal reflections are present on the network If you receive this indication check the network for impedance mismatches inadequate coaxial cable used for all or part of the trunk cable no termination or wrong termination high contact resistance or intermittent contact in BNC connectors near the taps Generally the faults are reported at the lower threshold settings and disappear or decrease at the higher settings Use the Bargraph mode to verify the minimum signal level If the signal level is low 2 or less on the Bargraph scale check the trunk cable length versus the number of nodes and compare it to the ControlNet specification Terminate any unused taps with a dummy load 1786 TCAP Also ensure that no BNC connector is in contact with any conductive material such as a metal wireway or DIN rail FATTA An unused drop cable should be terminated by a dummy load 1786 TCAP Do not use a 75 ohm termination along with a bullet connector The impedance here is not 75 oh
14. ld 1s raised Publication 1788 UM001A US P November 1999 Use the table below as a guideline when evaluating your network Threshold SW3 L O M H Network quality at the point of test No Fault No Fault No Fault Very clean Fault No Fault No Fault Clean Acceptable Fault Fault No Fault May be acceptable after cabling inspection Fault Network needs inspection If faults are reported for all three threshold levels then it is highly probable there is a severe problem on the network The third type of fault detection Slow Edges checks for a low signal with poor rising and falling edges caused by an abnormal attenuation of the signal This fault detection is not dependent on the threshold setting 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 meet the ControlNet requirements Examine the nodes that are reported faulted the Node On Line LED appears red or yellow and analyze the messages the faults may come from signal distortion signal weakness poor edges noise or signal reflections TIP Remember that the NetChecker s purpose is to alert for possible problems w
15. ld is made higher This fault is often reported along with Poor Signal Quality Illegal Framing most likely indicates a high level of signal reflections on the network see previous section but can also be caused by a faulty node A faulty node can be suspected if e only Illegal Framing is reported itis 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 LED for each of the known addresses of your network The faulty node is signalled by the Node On Line LED turning red Publication 1788 UM001A US P November 1999 16 Slow Edges Slow Edges has the following indications LED State TRAFFIC Green Slow Edges Blinking Red legal Framing May also be blinking Red Poor signal Quality May also be blinking Red Pass Fail Yellow or Red Buzzer Sounds Slow Edges is generally reported when a weak input signal with poor slow rising falling edges is identified This may occur with signals received from remote stations on long networks with a large number of nodes In this case Slow Edges detection is not influenced by the threshold setting on SW3 Make sure that the cable length versus number of nodes meets the ControlNet specification Check for possible high signal attenuation caused by inadequate coaxial media used for the trunk cable or segments High r
16. llegal Framing are detected they are signalled only by the buzzer The Slow Edges detection is not performed in Bargraph mode Bargraph Scale The Baregraph is not a precision voltmeter The LEDs are numbered from 1 dowest peak to peak voltage or Vpp to 7 highest Vpp Also note that the scale is not linear The following table shows the approximate peak to peak voltages indicated by each LED LED 7 will turn red if the signal level exceeds 9 5 Vpp Otherwise it will be off LED 1 can have one of three states red if the signal input is less than 0 75 Vpp green if the signal input is between 0 75 and 2Vpp and off under any other condition LEDs 2 to 6 can only be green or off PO oO S oO OJIN Only two LEDs on the Bargraph can be turned on at the same time one indicating the maximum level and the other indicating the minimum If the maximum and the minimum levels are the same only one LED will turn on Viewing a Node Signal Level in Bargraph Mode To check the signal level from a particular node set SW3 to the rightmost position and set the address of the node on the 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 LEDs are off the NetChecker does not detect any signal from a node having the address entered Publication 1788 UM001A US P November 1999 ThidseQia n networks
17. ms In disorders caused by impedance 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 Publication 1788 UM001A US P November 1999 15 In cases where the received signal has a low level less than 2 on the Bargraph scale with distortion and or poor edges the faults may appear or their recurrence may increase as the threshold is increased Make sure that the cable length versus number of nodes does not exceed the ControlNet specification Check for possible high signal attenuation caused by inadequate coaxial media used for the trunk cable or segments High resistance at the contact points of the BNC connectors on the trunk cable may also add abnormal signal attenuation Illegal Framing Illegal Framing has the following indications LED State TRAFFIC Green Slow Edges May also be blinking Red Illegal Framing Blinking Red Poor signal Quality May also be blinking Red Pass Fail Yellow or Red Buzzer Sounds Illegal Framing occurs if short messages or short between message gaps have been detected Illegal Framing detection is dependent on the threshold setting SW3 generally recurrence decreases as the thresho
18. neric Emission Standard Part 2 Industrial Environment e EN 50082 2 EMC Generic Immunity Standard Part 2 Industrial Environment This product is intended for use in an industrial environment Table of Contents PROUUCUOVEIVICW cen wats uc n ca R a etek ead ete State l NetChecker SpecinCatiOns 644uecmcns oreuscemanae eig eg aneen 3 TRAFFIC CED o ceceni e a aa Oa a AS 4 Modes of Network Analysis nnannnnnnana nanan 4 Diagnose ModE s saas teresine en ae Benen whee anA Da Hee AS 4 Tores hold Sea OS 7 54 04 iwi a aa oe Mh a aaa 5 LED EOC O besien eo Re a a a ee ones oe 5 BUZZER eeaeee EEEE Oe ERE E E EE A E A EN 7 Node Finder and Oscilloscope Output 0 0 00 c eee eee fi Barsraph Mode corsier o srera ia TEA ASEET 7 Barsraph Cale A434 Biota ae oboe Caen aa a 8 Viewing a Node Signal Level in Bargraph Mode 8 Performing a Global Survey of Signal Levels 9 Oscilloscope Output in Bargraph Mode 0 0 9 OperalOlus vanes eeu Keeney steele ta bude bones ee eoad 10 Installing the Batteries aneian ga hatha 4 doedd noses batted dea oe 10 Conserving Battery Power oaci3 oie chs ek one RAS ee ee 10 Using a Wall Adapter to Power the NetChecker 10 Connecting to the Network 0 0 0 ccc ee tee eens 1 Selecting Testpoints on the Network 00 cece eee eens 1 Network Diagnostics yn2terd ou Ah eee dee ses oA soe a mene wee fie 12 How t
19. ng is so marked IEC 1000 4 2 ESD susceptibility e IEC 1000 4 3 Radiated immunity CE e IEC 1000 4 4 EFT B immunity e IEC 1000 4 6 conducted RF immunity TRAFFIC LED This bi color LED 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 LED 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 LED to turn green e Red Low Battery If the batteries are low the LED will turn red whether ot not the tool is connected to a network Modes of Network Analysis The NetChecker offers two modes of analysis to evaluate a network e Diagnostic Mode provides a global network evaluation It is selected when slide switch SW3 is in the L M or H position e 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 Publication 1788 UM001A US P November 1999 Threshold Settings Sensitivity to Noise SW3 Position Reference Voltage Volts peak to peak mV Most Sensitive
20. o Begin Checking Your Network 000005 12 Faults and Their Origins osne rastris idea a a 12 Poor Signal Quality 43 6 5 eei heete e aE E iate wo 14 Tile cal Praline 2 2 0 odie ota ae eee E eee 15 SOW BOGESs ilo Bin bidet de ketone eae cee dels wanes 16 BX ITI Ns vases sce cece amp tae Sete Sun sd acd lv ete dae dink Sed 17 Checking the Signal Level Using the Threshold Setting 17 Checking the Signal Level Using the Bargraph 18 Additonal TIPS 2 56 voces bade eset ues eed oh eh d eee eee 19 Intermittent Probles os 2b t ee Gus a 8s OSA eae ees 19 Continuous Network Monitoring 0c ccc cee eee ees 19 Publication 1788 UM001A US P November 1999 il Table of Contents Example Waveforms Ideal Transmitted Packet on ControlNet as seen at transmitting node 00 eee A 1 Ideal Received Packet on ControlNet as scen at receivino Node herent se ee kote A eee wt A 2 Typical Waveforms 2 0 3 49059 6 04 55 400s 8254 45 44 9084S FOES E Rees A 2 Example of Waveform Seen When Network is Improperly Terminated 0 0 cece cee eee A 3 Effect of Attenuation on Signal Edges 00005 A 4 Publication 1788 UM001A US P November 1999 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 C
21. ontrolNet installations by verifying signals on the ControlNet cabling Using it installers are able to find shorts termination faults etc 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 e level of distortion noise or signal reflections rising and falling edges e 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 LEDs 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
22. oration Printed in USA
23. rk Diagnostics This section describes procedures for evaluating the quality of the ControlNet network How to Begin Checking Your Network Start checking in Diagnostic mode You can start checking at any of the three threshold settings L M and H but be sure to perform the test at all three settings Then set SW3 to the Bargraph rightmost position and examine the global signal level on the network by setting the Node Finder thumbwheels to 00 If you obtained the following results the NetChecker did not detect any problem at the testpoint LED State TRAFFIC Green Pass Fail Green Fault LEDs All Off for all thresholds L M and H Buzzer Does not sound Bargraph indication Within range of 2 to 6 Refer to the table in the following section to determine the overall state of your network Faults and Their Origins The NetChecker checks for Poor Signal Quality Illegal Framing and Slow Edges If a fault is detected when checking in the Diagnostic mode the buzzer will sound and one or more of the three fault LEDs will blink red The detection of Poor Signal Quality and Illegal Framing depends on the threshold setting on SW3 Generally faults that are detected at the L Low threshold level will disappear or be seen less frequently as the threshold is increased However in some cases where the received signal has a low level less than 2 on the Bargraph scale faults may appear or their recurrence may increase as the thresho
24. sh ON Slow Edges Node Finder Illegal Framing 3 Poor Signal 5 Quality Pass Fail 1 Min ee Push ON ot on avoc P 0 25A ControNet NetChecker Rockwell Allen Bradley Automation Bargraph Node Level 19 If LED 1 is green the minimum level is between 0 75Vpp and 2Vpp this is still acceptable If LED 1 is red however at least one signal is being received at a level less than 750mVpp To identify the node s that are producing the low signal s scan all of the node addresses on the network with the Node Finder If it is necessary to ensure that the signal at each node input meets the ControlNet Receive Mask specification 510mVpp at minimum verify the minimum level with an oscilloscope connected to the NetChecker If LED 7 top of the scale 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 Additional Tips Intermittent Problems Various intermittent problems are often are caused by the BNC connectors on the trunk cable e g center pin not crimped causing an unreliable contact The NetChecker in Diagnostic 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 Continuous Network Monitoring
25. ssary a few seconds to read the LEDs 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 Using a Wall Adapter to Power the NetChecker The NetChecker may also be powered by a wall adapter connected to the External Power connector on the side of the tool The adapter should produce a regulated 5 VDC 0 25A 5 5 volts max The internal batteries are disconnected when the adaptet s jack is inserted in the connector The NetChecker remains operating as long as power is provided switches SW1 and SW2 are not active in the external power mode however it is better to leave SW1 in the OFF position Make sure that your adapter is CE compliant and that the system formed by the NetChecker plus the adapter is also CE compliant Publication 1788 UM001A US P November 1999 11 Connecting to the Network Connect the NetChecker to the network using either a standard controlNet tap or the BNC T and cable provided If you do not want to open the network you can install some free 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 When you press the ON switch the TRAFFIC LED should turn green
26. to indicate that messages are being detected The greater the volume of traffic seen on the network the brighter the LED will be illuminated If the LED remains off the network is either inactive or the tested segment of cable 1s disconnected from the network Check the cable and the connectors Selecting Testpoints on the Network Good diagnostic results verify that the network signal is clean at the point of test only Because the defects caused by a single impedance mismatch are variable along the cable and are also related to the node that is transmitting a network segment should be tested at several points For example test near the two ends of the cable and at one or more points along the cable depending on the cable length and the number of nodes If repeaters are used every segment between repeaters should be checked On a redundant network check both of the cables The NetChecker 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 see Additional Tips on page 19 Keep in mind that the source of a problem may be far away from the point of analysis TIP A bad diagnostic result does not necessarily mean that the network is not functional However it may require a D gt closer check of wiring component quality connectors impedance matching etc Publication 1788 UM001A US P November 1999 12 Netwo
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