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Siemens LC 500 Cable, Selecting the correct instrumentation cable, Interconnection, Example

Models: Sitrans

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Cable

Interconnection

Cable

Notes:

•To maintain reliable transfer of the HART modem signals, the RC1 time constant of the connections should be less than 65 µSec.

•Cable capacitance must also be considered when selecting cable for intrinsically safe installations.

•For output signals (from the SITRANS LC 500), only the cable and barrier resistance are relevant. For input signals the measurement resistance is also relevant.

•Use twisted pair cable, screened as a pair.2

1.RC = Resistance * Capacitance

2.Or, if you use a common screen over a cable containing multiple twisted pairs, do not use other pairs for signals that could interfere with HART signals.

Selecting the correct instrumentation cable

•you need to know the cable length, the barrier type (if applicable), and the measurement resistance

•select a cable that will give you a capacitance time constant of less than 65 µSec

1.Calculate the capacitance for a time constant of 65 µSec, using the following formula:

t = R ⋅ C (time constant = Resistance * Capacitance) R is the sum of the load resistor and cable resistance.

C is the sum of the cable capacitance and the capacitances of the connected device/devices.

2.Determine the cable length allowed, by subtracting the capacitance value of the device (or devices) on the loop from the total capacitance, and using the maximum allowable limit of 100 pF per meter (or 1 nF per 10 meters).

Example

1.Calculate the cable capacitance which will give a time constant of 65 µSec:

A twisted pair cable with a conductor cross-section of 1 mm2 (AWG 18 equivalent) has a copper resistance of 73.6 Ohm/km and a capacitance of 100 pF/m (or 1 nF/10m).

For a standard 28 V 280 Ohm barrier and a 250 Ohm measuring resistance, with a

100 meter cable:

Resistance = 280 (barrier) + 250 (sensing device) + 7.36 (cable)= 537.36

t = R ⋅ C C = t ⁄R

65 ⋅ 10 – 6 s = 537.36 ⋅ C nF

C = (65 ⋅ 10 – 6 ⁄537.36)= 121 nF

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SITRANS LC 500 – INSTRUCTION MANUAL

7ML19985GE01

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Siemens LC 500, Sitrans instruction manual Cable, Selecting the correct instrumentation cable, Interconnection, Example

Contents

sitrans Instruction Manual JanuarySafety Guidelines Copyright Siemens Milltronics ProcessDisclaimer of Liability Qualified PersonnelTechnical Specifications SITRANS LC Table of ContentsTable of Contents SITRANS LC 500 Probe ConfigurationTroubleshooting SITRANS LC Table of ContentsMaintenance Error Messages and Error CodesAppendix E SITRANS LC 500, alternate versions and application details Table of ContentsAppendix D Block Diagram, and Correlation table, mA to % Appendix C HART DocumentationAppendix F Approvals Table of ContentsQuick Reference SITRANS LC GlossarySITRANS LC ApplicationsIntroduction The Manual Safety NotesSafety marking symbols IntroductionLong Form Abbreviations and IdentificationsShort form DescriptionEnvironmental PowerSpecifications PerformanceCommunications OutputsUser Interface SpecificationsWetted Parts WeightElectrodes Enclosure electronicSpecifications Process ConditionsApprovals Lloyds Register of ShippingThe SITRANS LC 500 variable frequency oscillator SITRANS LC 500 TransmitterOperating Principles Operation & ApplicationNon-conductive or conductive contents Operation & ApplicationThe formula 1 is C = In a non-conductive or irregular tank The SITRANS LC 500 electrodeOperation & Application The stilling wellOperation & Application Measurementf ≈ Application SITRANS LC Operation & Applicationauxiliary Level MeasurementOperation & Application deactivation hysteresis2-state Switch Switch actionInterface Measurement Solid-state SwitchVia HART Fault SignallingVia the loop current Via the solid-state outputSITRANS LC 500 Probe Configuration SITRANS LC 500 Electrode Probe CharacteristicsProbe Configuration Process Connections Electrode AssemblyProcess Connection and Seal Configuration of SITRANS LC Seal TypesPressure and Temperature Considerations Probe ConfigurationNon-Standard Application SITRANS LC 500 ConfigurationNon-standard applications Probe ConfigurationSITRANS LC 500 Installation InstallationHandling Electrodes Process Cautions Protection for solid-state switchMounting Instructions InstallationSITRANS LC 500 Standard Level Version InstallationSupply WiringInterconnection SITRANS LC InterconnectionInterconnection CableSelecting the correct instrumentation cable ExampleMulti-drop applications maximum cable length IS applications maximum cable lengthIIB type/class hazardous area applications maximum cable length InterconnectionTerminals Connecting SITRANS LCConnection Diagram InterconnectionInterconnection Grounding instructionsProtection for solid-state switch ground lug label / protective seal DO NOT REMOVEMetal Tanks Grounding Examples SITRANS LCSystem Grounding referencing InterconnectionSITRANS LC 500 can be connected to the tank as shown Cathodically Protected Metal TanksNon-Conductive Tanks PageGND COAX Safety GroundingInterconnection COAX GNDnon-hazardous area PageStahl barrier 9002/13-280 Communications DiagnosticsTypical PLC configuration with HART Interconnection1. See Calibration using push-button adjustment on page Current values used as signals from digital transmittersApplications for Solid-state Output InterconnectionSettings Factory SettingsSwitch Protection Diode SettingSetting DescriptionInterconnection The SITRANS LC 500 User Interface The LCD displayUser Interface Menu Group How to access the dataMenu Levels 00 to 0F and 10 to 1F DetailsAdjusting the value The rotary switchAccess to a menu item The push-buttonsUser-defined Functions Transmitter VariablesTransmitter Variable UnitsStart Up Start-up SITRANS LCQuick Start Quick Start SequenceRotary Switch Positions - Quick Reference Start up using push-button calibration overview Menu levels 0 andStart Up Calibrate the 100% setting URV - upper range value menu 0F Calibration using push-button adjustmentCalibrate the 0% setting LRV - lower range value menu 0E Start UpExample Start UpChanging stepsize value menu ExampleStart Up Calibration using HART Start UpFor situations where the capacitance values are known in advance Start Up129 Adjust for Product Build-up on Sensor Number Description38 Reset Configuration Changed Flag 128 Set Alarm Select Start UpStart Up NumberDescription 7ML19985GE01Test function MaintenanceMaintenance InspectionsMaintenance b. Confirm that Menu 08 is set to enable analog fault signalling display should readTroubleshooting SITRANS LC TroubleshootingError Codes HART Error Messages and Error CodesError Messages push-button operation ErrorAppendix A Menu Groups Analog Output Signalling loop currentDigital Output Signalling solid-state output Appendix AAppendix A Transmitter Variable Settings menu levelMenu Items MenuAppendix A Range 0 toRange 1 to 10,000 Affected Appendix AMenu Left ArrowRange 0.00 to Factory settingAppendix A Probe capacitance inProbe capaci Transmitter Variable Values menu levelAppendix A Display showsDynamic Value PV Appendix ATV0 values displayed as % Units or % of range, selectedRotary SwitchTransmitter Variables Dynamic Value menu level LeftMenu Analog Output Signalling proportional or 2-state menu levelAppendix A AffectedAppendix A Menu Analog Signalling Mode 2-state menu levelAppendix A AffectedAffected Appendix AMenu Description2-state High Fault Sig Appendix AMenu Digital Output Signalling solid-state output menu levelAppendix A AffectedAffected Appendix AMenu ArrowAppendix A S co Appendix AS cc hold RED +Description Appendix AMenu PositionMiscellaneous Appendix AAppendix A Disables 2-buttonDisables 1-button LeftAppendix B LCD display examples LCD alphanumeric display examplesAppendix B HART1 Communications for the SITRANS LC Appendix C HART DocumentationHART information HART Device Descriptor DDSITRANS LC 500 DD Menu/Variable Organization Appendix C7ML19985GE01 Bit #7 Field Device Malfunction Bit #6 Configuration ChangedHART Response Code Information Bit #5 Cold StartUsage HART Conformance and Command ClassCommand Appendix CNon-volatile Memory Data Storage General Transmitter InformationDamping information CommandBurst mode Additional Universal Command SpecificationsMultiDrop operation Units conversionsAppendix D Block Diagram, and Correlation table, mA to % SITRANS LC 500 Block DiagramCurrent in mA Correlation Table 0% - 100% to 4-20 mA or 20-4 mARange 0 - 100 % Appendix DAppendix E Standard VersionStandard Version S-Series, Threaded Appendix E SITRANS LC 500, alternate versions and application detailsFeatures Standard Version S-Series, Threaded Standard Version S-Series, ThreadedAppendix E S-Series, Welded Flange Standard Version S-Series, Welded and Machined Flanged VersionsFeatures Standard Version S-Series, Flanged Appendix EFeatures Standard Version DD-Series Standard Version D-Series, Machined FlangeFeatures Standard Version D-Series redundant safety e.g. Phenol, Phosgene applications, etcredundant safety e.g. Phenol, Phosgene applications, etc Features Standard Version, Probe/ Thermal IsolatorFeatures Standard Version SD-Series Appendix EProcess Connection Size Interface VersionAppendix E OptionsSanitary Versions, threaded and tri-clamp Sanitary VersionFeatures Sanitary Version, Tri-Clamp Sanitary Thread CouplingAppendix E FlangesFlange Standards 7ML19985GE01Dimensions in feet Applications ExamplesGeneric Application Calculations Appendix ELarger tank, dimensions in feet Appendix E7.32 ⋅ Appendix E Application level indicator and solid-state switch outputDevice settings 90.0Appendix E Application Analog fault signalling 2-state outputDevice settings 90.0Appendix E Menu 0B readsSITRANS LC 500 / Pointek CLS Appendix F ApprovalsCE Certificate Appendix FSCHRIFTLICHE KONFORMITÄTSERKLÄRUNG CE BescheinigungSITRANS LC 500 / Pointek CLS Appendix FInstrument label SITRANS LC Appendix F7ML19985GE01 KEMA certificate and schedules Appendix FPage SITRANS LC 500 - INSTRUCTION MANUAL Appendix FPage 7ML19985GE01SITRANS LC 500 - INSTRUCTION MANUAL Appendix F7ML19985GE01 PageSITRANS LC 500 - INSTRUCTION MANUAL Appendix FPage 7ML19985GE01SITRANS LC 500 - INSTRUCTION MANUAL Appendix F7ML19985GE01 PageSITRANS LC 500 - INSTRUCTION MANUAL Appendix FPage 7ML19985GE01SITRANS LC 500 - INSTRUCTION MANUAL Appendix F7ML19985GE01 PageSITRANS LC 500 - INSTRUCTION MANUAL Appendix FPage 7ML19985GE01Application Certificates and ApprovalsNAMUR recommendation NE SpecificationsApproval Appendix FPage 108 SITRANS LC 500 - INSTRUCTION MANUAL Hazardous Classified LocationGlossary GlossarySITRANS LC 500 - INSTRUCTION MANUAL GlossaryPage 7ML19985GE01Index Indexelectrode characteristics 16 electrode specifications Indexconnect diode Quick Start Quick Reference SITRANS LCQuick Reference Quick Start SequenceRotary Switch Positions - Quick Reference Page Siemens Milltronics Process Instruments Inc 7ml19985GE01Tel 705 745-2431 Fax 705 Email techpubs@siemens-milltronics.com Subject to change without prior notice