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Yokogawa NFAI841-S00/A4S00 Analog I/O Module

Configured for simultaneous 4-20 mA signal acquisition and analog current output control in CENTUM VP and CENTUM CS 3000 systems, the Yokogawa NFAI841-S00/A4S00 (NFAI841 Analog I/O Module) provides direct electrical interfacing with field devices while maintaining system-level isolation.

Suffix Breakdown & Model Matrix

• NFAI841: Mixed analog input/output module family for Yokogawa FIO systems
• -S00: Standard type without HART communication or explosion protection
• /A4S00: Terminal block configuration for pressure-clamp or standard field wiring

Hardware Specifications

Parameter	Specification
ModelBrand	Yokogawa NFAI841-S00/A4S00
Origin	Japan
Weight	Approx. 0.35 kg
Dimensions	Not specified
OperatingTemp	0 degC to 60 degC
PowerConsumption	5 VDC max 230 mA, 24 VDC max 190 mA
Input Signals	4-20 mA DC
Output Signals	4-20 mA DC
Channels	4 input + 4 output
Input Impedance	250 ohm
Output Load Resistance	0 to 750 ohm
Accuracy	Input +/-0.1% FS
Refresh Cycle	10 ms
Isolation	Channel-to-channel and system-to-field isolation
Withstand Voltage	1500 VAC

Yokogawa DCS Analog Loop & Channel Isolation

The NFAI841-S00/A4S00 module features galvanic isolation between each analog channel and the system internal circuits to prevent ground loop interference. 4-20 mA loops support HART overlay signaling for device diagnostics and configuration without additional cabling. Each analog input and output channel maintains independent signal referencing, ensuring integrity during simultaneous acquisition and actuation. Cold junction compensation (CJc) is implemented to maintain accuracy over the specified temperature range.

Frequently Asked Questions

Q: Can this module be hot-swapped during operation?
A: Yes. The module supports hot-swappable insertion and removal under power, but dual-redundant loop configuration is recommended for critical PID loops to prevent transient signal loss.

Q: What is the maximum output load allowed?
A: Output channels can drive loads up to 750 ohm. Exceeding this may result in current clipping or voltage saturation.

Q: How is channel isolation maintained?
A: Each input and output channel is isolated using photo-coupled barriers, preventing cross-talk and ground loop interference while maintaining full compliance with DCS system safety limits.

Field Installation Guidelines

• Use twisted-pair shielded cable for all analog loops; terminate shields at a single cabinet ground point
• Maintain physical separation from high-voltage power conductors to reduce induced noise
• Confirm correct loop polarity before energizing modules
• Ensure secure module seating and proper backplane engagement to avoid intermittent contacts
• Avoid exceeding specified ambient temperature (0-60 degC) and humidity (10-90% RH) for stable operation
• Check terminal block wiring per /A4S00 configuration to ensure consistent current loop connectivity

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