Product Overview

The Yokogawa NFAI835-S51 is an analog input/output module. This device provides 4 analog input channels and 4 analog output channels. All channels are fully isolated for noise immunity.

HART communication is supported on the analog signals. Additionally, the module includes RTU, WTR, and PCT compatibility. For field wiring, a 40-pin MIL connector is provided. Consequently, this versatile module suits a wide range of process control applications.

General Specifications

The NFAI835-S51 offers robust analog I/O capabilities for demanding environments.

• Manufacturer: Yokogawa.

• Product Type: Analog Input/Output Module.

• Number of Input Channels: 4 (4 to 20 mA).

• Number of Output Channels: 4 (4 to 20 mA).

• Channel Isolation: Yes (isolated channels).

• Weight: 0.3 kg.

Compatibility Features:

• HART: Yes.

• RTU: Yes.

• WTR: Yes (-20).

• PCT: Yes.

• MIL: Yes, 40 pins.

Accuracy and Performance Specifications

The NFAI835-S51 delivers high precision for demanding measurement and control applications.

• Input Accuracy: ±0.1% of full scale.

• Output Accuracy: ±0.3% of full scale.

• Data Refresh Cycle: 10 ms.

• Input Step Response Time: 100 ms.

• Output Step Response Time: 100 ms.

• Temperature Drift: Max. ±0.01% /°C.

Electrical Specifications

The NFAI835-S51 includes comprehensive electrical ratings for reliable operation.

Withstanding Voltage:

• 500 V AC between input/output and system.

• 500 V AC between channels.

• Therefore, high noise immunity and ground loop prevention are achieved.

Transmitter Power Supply:

• Output Voltage: 20.2 to 29.3 V.

• Output Current Limit: 25 mA.

• Consequently, it powers 2-wire and 4-wire transmitters directly without external supplies.

Current Consumption:

• Max. Current (5V DC): 360 mA.

• Max. Current (24V DC): 450 mA.

Transmitter Configuration

The NFAI835-S51 offers flexible transmitter wiring options for various field devices.

• Two-Wire Transmitter Setting: Per channel with connected terminal.

• Four-Wire Transmitter Setting: Per channel with connected terminal.

• Output Fallback: Set for each channel independently.

Key Features

The NFAI835-S51 offers several advantages for analog I/O applications.

Dual Functionality:
Provides both analog inputs and outputs in a single module. Therefore, it saves rack space and reduces overall system cost.

HART Communication Support:
Allows digital communication over the 4-20mA loops. Consequently, configuration and diagnostics are possible from the host system without additional wiring.

Full Channel Isolation:
Withstands 500V AC between channels and between channels and the system. Hence, ground loops and cross-channel interference are completely eliminated.

High Accuracy Inputs:
Input accuracy reaches ±0.1% of full scale. For this reason, precise process measurements are guaranteed for critical control loops.

Fast Refresh Cycle:
Data refreshes every 10 ms. Thus, the module captures rapid process changes without significant delay.

Transmitter Power Supply Included:
Provides 20.2 to 29.3V at up to 25 mA per channel. Therefore, external power supplies may not be required for loop-powered transmitters.

Output Fallback per Channel:
Each output channel has independent fallback settings. As a result, outputs go to predefined safe states during communication loss or CPU failure.

Two-Wire and Four-Wire Support:
Configurable per channel for either 2-wire or 4-wire transmitters. Hence, maximum wiring flexibility is provided for various field devices.

Low Temperature Drift:
Maximum drift is only ±0.01% per degree Celsius. Consequently, accuracy is maintained across varying plant temperatures and seasonal changes.

Lightweight Design:
Weighs only 0.3 kg. Thus, it adds minimal weight to the rack and simplifies handling during installation.

Typical Applications

The NFAI835-S51 suits various process control applications across multiple industries.

• Pressure and flow monitoring with analog inputs.

• Valve position control with analog outputs.

• Temperature measurement and heater control.

• HART transmitter integration in CENTUM VP systems.

• Process I/O for small to medium control systems.

Installation Guidelines

Install the NFAI835-S51 in a compatible Yokogawa rack using standard procedures. First, ensure the backplane can supply 360 mA at 5V DC and 450 mA at 24V DC. After that, connect field devices to the 40-pin MIL connector.

Analog Input Wiring:
For analog inputs, connect 4-20mA signals from transmitters. When using two-wire transmitters, the internal supply provides 20.2-29.3V at up to 25 mA. In contrast, four-wire transmitters require external power.

Analog Output Wiring:
Turning to analog outputs, connect 4-20mA signals to actuators or positioners. The output step response time is 100 ms. Additionally, set output fallback values for each channel.

Communication Setup:
The data refresh cycle is 10 ms. HART communication is supported on both inputs and outputs. Therefore, digital device configuration is possible without additional hardware.

What is in the Box

Please inspect all items upon delivery.

• Yokogawa NFAI835-S51 analog input/output module.

• 40-pin MIL connector (for field wiring).

• Installation instruction manual.

Frequently Asked Questions (FAQ)

1. How many input and output channels does the NFAI835-S51 have?

The NFAI835-S51 has 4 analog input channels and 4 analog output channels. All channels are 4-20mA and fully isolated.

2. Does this module support HART communication?

Yes. The NFAI835-S51 supports HART communication. Therefore, digital device configuration and diagnostics are available without additional hardware.

3. What is the accuracy of the analog inputs?

The input accuracy is ±0.1% of full scale. The output accuracy is ±0.3% of full scale. Temperature drift is a maximum of ±0.01% per degree Celsius.

4. What is the data refresh cycle for this module?

The NFAI835-S51 has a data refresh cycle of 10 ms. The step response time for both inputs and outputs is 100 ms.

5. Does the module provide transmitter power?

Yes. The NFAI835-S51 provides a transmitter power supply of 20.2 to 29.3V. The output current limit is 25 mA per channel. Consequently, it can power two-wire loop-powered transmitters directly.