RTD (Module G4)68C3 Operations Manual North Atlantic Industries, Inc. 12/19/2014Rev: 2014-12-19-0947 www.naii.com Page 154 of 330RTD (MODULE G4)Principle of OperationModule G4 provides six resistance temperaturedetectors (RTD) measurement channels. Eachchannel is configurable for use with the 4-wire, 3-wireor 2-wire RTD devices. The 4-wire mode (default) isthe most accurate, providing excellent stability andrepeatability. All RTD channels are self-calibratingbecause each channel is automatically calibrated toeliminate offset and gain errors. Open inputs will bedetected, with the results displayed in a status word.All inputs are double buffered for immediateavailability. External excitation is not required. Thereare six programmable full-scale ranges designed around the three most common RTD devices:200Ω, 400Ω, 800Ω, 2000Ω, and 4000Ω from -260°C to +850°C (except for the highest range which is limited to6500Ω or about +640°C).DRV+SNS+SNS-DRV-RTD(I/F fromCard)4-WireRTDDRV+SNS+SNS-DRV-RTD(I/F fromCard)3-WireRTDDRV+SNS+SNS-DRV-RTD(I/F fromCard)2-WireRTDFigure 1: Typical RTD Module ConnectionsBuilt-In-Test (BIT) / Diagnostic CapabilityAutomatic background BIT testing, where each channel is functionally checked for correct A/D operation using adedicated test resistor and also monitors for any open leads. Any failure triggers an interrupt (if enabled) with theresults available in status registers. The testing is totally transparent to the user, requires no externalprogramming and has no effect on the operation of this card. It can be enabled or disabled.ProtectiveCircuits16AD & Wrap-Around TestCircuit 1AD & Wrap-Around TestCircuit 6StateMachineRTD Module Block DiagramModule BusUser Interface
