Safety Considerations Guide, Tricon v9.0 - Tuv-fs.com

44 Module Diagnosticsfield power or a field short condition. The alarm can be used to modify the controlstrategy or direct effective maintenance action.Analog Input ModulesAnalog Input Module points use a combination of comparison and referencediagnostics. Under system control, each channel is independently comparedagainst the measured value of all channels. If a mismatch if found, an alarm is set.Each channel’s measured values are also compared its against internal references.A channel that has detected a fault on an analog input point votes that point to bezero. Using these diagnostics, each channel can be verified independently, thusassuring near 100% fault coverage and fail-safe operation under all single-fault,and most common, multiple-fault scenarios.Analog Input Module AlarmsAnalog Input Module faults are reported to the control program. These alarms canbe used to increase availability during specific multiple fault conditions. Loss oflogic power is reported to the control program.Analog Output ModulesAnalog Output Modules use a combination of comparison and referencediagnostics. Under system control, each channel is given control of the outputsequentially using the 2oo3 voting mechanism. Each channel independentlymeasures the actual state of an output value by comparing it with the commandedvalue. If the values do not match, a channel switch is forced by voting anotherchannel. Each channel also compares its measured values against internalreferences. Using these diagnostics, each channel can be independently verified forits ability to control the analog output value, thus assuring nearly 100% faultcoverage and fail-safe operation under all single-fault, and most common,multiple-fault scenarios.Analog Output Module Field AlarmsAnalog Output Module faults are reported to the control program. These alarmscan be used to increase availability during specific multiple-fault conditions. Lossof field power or logic power is reported to the control program.Tricon Safety Considerations Guide