NFAR181-S50/R8S10

The Yokogawa NFAR181-S50/R8S10 is a 12-channel resistance temperature detector (RTD) input module designed to acquire temperature signals from three-wire Pt100 sensors. It provides isolated input channels for temperature measurement and connects to external RTD wiring through a pressure-clamp terminal block with surge absorber. The module converts sensor resistance into temperature data for processing by the control system.

Functional Description

The NFAR181 receives resistance signals from connected RTD sensors and converts them into digital temperature measurement data. Its 12-channel configuration allows multiple temperature points to be monitored through one module.

Channel isolation separates the input circuits, helping limit electrical interference and unwanted signal coupling between measurement points. This is useful when monitoring temperature sensors installed at different locations or connected to electrically distinct equipment.

RTD Input Specifications

The module supports Pt100 and JPt100 three-wire RTD sensors. The three-wire measurement arrangement compensates for lead-wire resistance, provided the resistance of each wire is equal. The allowable wiring resistance is 40 ohms per wire, which should be considered when selecting sensor cables and planning field connections.

The specified RTD measurement current is 1 mA. The measurement accuracy is rated at +/-0.03% of full scale over the 0 to 400 ohm input range. A 1-second data refresh cycle makes the module suitable for process temperature monitoring where this update interval meets the application requirements.

Terminal Block and Surge Protection

The /R8S10 option identifies a pressure-clamp terminal block for RTD connections with a surge absorber. This provides the external wiring interface for connecting the field RTD sensors to the module.

The terminal block configuration should be checked against the existing field wiring arrangement when replacing an installed module. The terminal block option is part of the complete ordering configuration and should not be treated as interchangeable with other connection options without verification.

Technical Specifications

Parameter	Specification
Model	NFAR181-S50/R8S10
Brand	Yokogawa
Product Type	RTD Input Module
Number of Input Channels	12, isolated
Input Signal	Pt100, JPt100
Sensor Connection	3-wire RTD
Measurement Current	1 mA
Input Resistance	2 Mohm or more
Allowable Input Voltage	+/-5 V
Accuracy	+/-0.03% of full scale (0 to 400 ohms)
Allowable Wiring Resistance	40 ohms per wire
Data Refresh Cycle	1 second
Withstanding Voltage	1500 V AC for 1 minute (input to system)
Burnout Detection	Available, configurable for all channels
Burnout Detection Time	60 seconds
Maximum Current Consumption	450 mA at 5 V DC
External Connection	Pressure-clamp terminal block
Terminal Block Option	/R8S10, with surge absorber
Weight	0.2 kg

Frequently Asked Questions

Q: Which RTD sensor types are supported by the NFAR181-S50/R8S10?

A: The module supports Pt100 and JPt100 resistance temperature detectors in three-wire configurations. Thermocouple and millivolt inputs belong to other module types and should not be assumed to be supported by this RTD module.

Q: What is the difference between the /R8S00 and /R8S10 configurations?

A: Both options use a pressure-clamp terminal block for RTD connections. The /R8S10 version includes a surge absorber, whereas /R8S00 is the version without the specified surge absorber.

Q: What should be checked when replacing an existing NFAR181 module?

A: Verify the complete model number, RTD sensor type, three-wire connection arrangement, terminal block configuration and system compatibility. The 40 ohm per-wire resistance limit should also be checked against the installed field wiring.

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