1756-RM001B-EN-P, Using ControlLogix in SIL2 ... - Tuv-fs.com

ControlLogix I/O Modules 6-13Using Analog InputModulesThree ControlLogix analog input modules are certified for use SIL2applications. Table 6.4 lists the modules.Table 6.4 ControlLogix Analog Input Modules Suitable for SIL2 ApplicationsCatalog Number:1756-IF81756-IR6I1756-IT6IDescription:Single-ended analog input moduleIsolated RTD analog input moduleThermocouple/mV analog input moduleGeneral Considerations when using Any ControlLogix AnalogInput ModuleThere are a number of general application considerations that youmust follow when applying these modules in a SIL2 application:• Proof Tests - Periodically (for example, once every severalyears) a System Validation test must be performed. Manually, orautomatically, test inputs to make sure that all inputs areoperational. Field signal levels should be varied over the fulloperating range to make sure that the corresponding channeldata varies accordingly. For additional information on ProofTests, see page 1-5 and Figure 9.1 on page 9-5.• Calibrate Inputs Periodically, As Necessary: ControlLogixI/O modules ship from the factory with a highly accurate levelof calibration. However, because each application is different,users are responsible for making sure their ControlLogix I/Omodules are properly calibrated for their specific application.Users can employ tests in application program logic todetermine when a module requires recalibration. For example,to determine whether an input module needs to be recalibrated,a user can determine a tolerance band of accuracy for a specificapplication. The user can then measure input values on multiplechannels and compare those values to acceptable values withinthe tolerance band. Based on the differences in the comparison,the user could then determine whether recalibration isnecessary.Calibration (and subsequent recalibration) is not a safety issue.However, we recommend that each analog input be calibrated atleast every 3 years to verify the accuracy of the input signal andavoid nuisance application shutdowns.Publication 1756-RM001B-EN-P - October 2003