Configured for industrial process measurement in DCS platforms, the Yokogawa NFAR181-S50 (NFAR181-S50 RTD Input Module) provides direct signal acquisition and galvanic isolation for RTD sensor inputs.

Hardware Specifications

Process Control and Measurement Accuracy

The module maintains signal integrity through active cold junction compensation (CJC) for temperature measurement circuits and provides robust channel-to-channel isolation. The input resistance is maintained at 2 MOhm or higher in both power-on and power-off states to prevent loading effects on the sensor loop. The internal measurement circuitry utilizes a 1 mA excitation current for Pt100 sensors, with a thermal drift characteristic of 30 ppm/deg C. System integration is supported via a 1-second data refresh cycle, with configurable burn-out detection thresholds for each of the 12 channels to facilitate early diagnostics of open-circuit or short-circuit faults in the field wiring.

Frequently Asked Questions

Q: Can the burn-out detection timing be adjusted for individual channels?

A: The burn-out detection is a global configuration feature within the module parameters, with a fixed detection window of 60 seconds.

Q: Does the 1500 V AC withstanding voltage rating apply to all I/O terminals?

A: The withstanding voltage rating of 1500 V AC for 1 minute is specified between the input signal terminals and the internal system backplane logic.

Field Installation Guidelines

1. Ensure the control system is powered down before inserting the module into the designated I/O rack slot.
2. Verify that the 3-wire RTD cabling is shielded to minimize electromagnetic interference, and terminate the shield at the specified system grounding point.
3. Check that the terminal block is securely locked into the module housing to maintain proper contact pressure for all 12 channels.
4. Confirm that the ambient temperature surrounding the I/O rack remains within the specified operational limits to ensure the accuracy of the internal compensation circuitry.
5. After installation, perform a loop test to verify that the digitized values in the DCS match the actual temperature input at the field sensor terminal.