Introduction
The Yokogawa NFAI835-S51 Analog Input/Output Module is a high-reliability hybrid I/O module designed for STARDOM FCN/FCJ distributed control systems (DCS). It integrates both analog signal input and output functions in a single compact unit, enabling efficient process monitoring and closed-loop control in industrial automation environments.
This module is engineered for 4–20 mA current loop applications, offering isolated channels, stable signal processing, and long-term operational consistency. The S51 suffix generally indicates an enhanced configuration variant (often aligned with ISA G3 environmental suitability and improved industrial robustness), making it suitable for demanding process environments.
Technical Specifications
| Parameter | Specification |
|---|
| Model | NFAI835-S51 |
| Manufacturer | Yokogawa |
| Type | Analog Input / Output Module |
| I/O Configuration | 4 AI / 4 AO (isolated channels) |
| Input Signal | 4–20 mA DC |
| Output Signal | 4–20 mA DC |
| Allowable Input Current | Up to 25 mA |
| Resolution | 16-bit A/D and D/A conversion |
| Accuracy | ±0.1% (input), ±0.3% (output) |
| Data Refresh Cycle | 10 ms |
| Input Step Response | 100 ms |
| Output Step Response | 100 ms |
| Load Resistance (Output) | 0–750 Ω |
| Isolation | Input/output and channel isolation (industrial grade) |
| Transmitter Supply | 20.2–29.3 V DC |
| Temperature Drift | ±0.01% / °C max |
| Power Consumption | ~360 mA (5 V DC), ~450 mA (24 V DC) |
| Operating Temperature | -20°C to +70°C (typical industrial range) |
| Weight | ~0.3 kg |
| Mounting | STARDOM FCN/FCJ base unit rack |
Applications
The NFAI835-S51 is widely used in industrial automation systems requiring both measurement and control capabilities.
Typical applications include:
-
Oil & gas production and pipeline control systems
-
Petrochemical and refinery process automation
-
Power generation and turbine control loops
-
Water treatment and utility monitoring systems
-
SCADA and DCS distributed control architectures
-
Industrial valve and actuator control systems
-
Continuous manufacturing process regulation
-
Environmental monitoring and instrumentation networks
Its hybrid I/O structure reduces system complexity while maintaining high signal integrity.
Advantages
The Yokogawa NFAI835-S51 delivers strong industrial and operational benefits:
-
Hybrid 4 AI / 4 AO architecture reduces hardware footprint
-
High-precision 16-bit conversion ensures accurate signal handling
-
Fast 10 ms refresh cycle supports real-time process response
-
Fully isolated channels improve electrical noise immunity
-
Stable 4–20 mA compatibility ensures broad industrial integration
-
ISA G3-enhanced variant (S51) supports harsher environments
-
Low drift performance ensures long-term measurement stability
-
Seamless integration with Yokogawa FCN systems
Technical FAQs
1. What is the main function of the NFAI835-S51?
It provides both analog input and output signal processing in one module.
2. How many channels does it support?
It supports 4 analog inputs and 4 analog outputs.
3. What signal type does it use?
Standard 4–20 mA current loop signals.
4. Is the module isolated?
Yes, it features channel-to-channel and system isolation.
5. What is the accuracy level?
±0.1% for inputs and ±0.3% for outputs.
6. What is the response time?
Approximately 100 ms step response time.
7. What is the refresh cycle?
Around 10 ms.
8. What does S51 mean?
It generally refers to an enhanced variant, often aligned with ISA G3 environmental specification options.
9. What is the weight?
Approximately 0.3 kg.
10. What system is it compatible with?
Yokogawa STARDOM FCN/FCJ distributed control systems.
A DCS Q Co., Ltd. - PLC and DCS Industrial Control Equipment Wholesale
