Yokogawa NFAI143-H50/A4AS0 Isolated Analog Input Module

The Yokogawa NFAI143-H50/A4AS0 is specified in the supplied information as a 16-channel analog input module for Yokogawa CENTUM VP and CENTUM CS 3000 distributed control systems. It accepts 4-20 mA DC signals from field transmitters and converts them into process data for control and monitoring. The stated configuration includes HART communication support, field-signal isolation, and transmitter power supply capability.

Input Channels and Signal Processing

The module provides 16 isolated input channels for 4-20 mA DC signals, with an allowable input current of up to 24 mA. Each channel can be configured for a 2-wire or 4-wire transmitter. This allows the module to accommodate different transmitter power arrangements within the supported system configuration.

The specified accuracy is +/-0.1% of full scale, with a 10 ms data refresh cycle and a 100 ms input step response time. These parameters describe the module's measurement accuracy, process-data update interval, and response to a change in the input signal, respectively.

HART Communication and Transmitter Power

The HART version supports digital communication with compatible smart field instruments over the analog current loop. HART communication can provide access to supported instrument parameters and diagnostic information in addition to the primary process measurement. The exact supported HART functions depend on the applicable module and system configuration.

The stated transmitter supply is 24.0 to 25.5 V DC, with a current limit of 25 mA. When using 2-wire transmitters, verify that the transmitter's supply and current requirements are within this limit. Four-wire transmitters use a separate power arrangement, which must be considered when planning field wiring.

Electrical Isolation and Power Requirements

The NFAI143 provides isolation between the input circuits and the system, with a specified withstand voltage of 1500 V AC for one minute. Integrated overcurrent protection is also specified. These features help limit the effects of electrical faults and potential differences between field wiring and the system side; they do not replace appropriate grounding and wiring practices.

The published maximum current consumption is 230 mA at 5 V DC and 540 mA at 24 V DC. The 24 V DC supply requirement for the analog field power circuit should be checked separately from the module's system-bus power consumption.

Technical Specifications

Parameter	Specification
Model	NFAI143-H50/A4AS0
Brand	Yokogawa
Product Type	Isolated Analog Input Module
Number of Input Channels	16
Input Signal	4-20 mA DC
Allowable Input Current	24 mA DC maximum
Input Resistance	250 ohm when powered on; 500 kOhm or more when powered off
Input Accuracy	+/-0.1% of full scale
Data Refresh Cycle	10 ms
Input Step Response Time	100 ms
Temperature Drift	+/-0.01%/deg C maximum
HART Communication	Supported by HART version
Transmitter Power Supply	24.0 to 25.5 V DC
Transmitter Supply Current Limit	25 mA
Transmitter Configuration	2-wire or 4-wire, selectable per channel
Isolation Withstand Voltage	1500 V AC for 1 minute, input to system
Overcurrent Protection	Provided
Maximum Current Consumption	230 mA at 5 V DC; 540 mA at 24 V DC
Weight	0.3 kg
External Connection	Pressure-clamp terminal or MIL connector cable, subject to the applicable terminal assembly

The electrical specifications above are based on Yokogawa's published NFAI143 module documentation. The exact /A4AS0 terminal and option configuration should be confirmed against the applicable ordering specification before replacement or procurement.

Frequently Asked Questions

Q: How many field transmitters can the NFAI143-H50/A4AS0 support?

A: The module provides 16 analog input channels. Each channel accepts a 4-20 mA DC signal, and the transmitter arrangement can be configured for 2-wire or 4-wire operation.

Q: Does this module support HART instruments?

A: The HART version supports digital communication with compatible HART field instruments. Confirm the required HART functions and system-side asset-management support before integrating it into an existing installation.

Q: What should be checked before replacing an installed module?

A: Verify the complete model number, including -H50/A4AS0, the terminal assembly and cable arrangement, the field power supply, and the controller platform. Do not assume that matching the NFAI143 base model alone establishes compatibility with the existing installation.

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