
Product Overview
The Yokogawa NFAI835 is a mixed Analog Input/Output Module designed for Yokogawa distributed control and industrial automation systems. It is used to both acquire analog signals from field instruments and output analog control signals to field devices within a single module.
This dual-function design allows it to handle process monitoring and control simultaneously, making it suitable for compact and flexible I/O configurations in industrial systems.
Technical Specifications
| Parameter |
Specification |
| Manufacturer |
Yokogawa |
| Model |
NFAI835 |
| Product Type |
Analog Input/Output Module |
| Input Channels |
4 channels (isolated) |
| Output Channels |
4 channels (isolated) |
| Input Signal |
4–20 mA DC |
| Output Signal |
4–20 mA DC |
| Resolution |
16-bit |
| Accuracy |
±0.1% (input), ±0.3% (output) |
| Channel Isolation |
Channel-to-channel and system isolation |
| Load Resistance |
0–750 Ω |
| Input Protection |
Overcurrent protection supported |
| Data Refresh Cycle |
10 ms |
| Step Response Time |
Approx. 100 ms |
| Power Supply |
24 V DC |
| Connector Type |
MIL connector / terminal block (system dependent) |
| Mounting Method |
Yokogawa controller base unit |
| Dimensions |
130 × 107.5 × 32.8 mm |
| Weight |
0.3 kg |
Function and Working Principle
The NFAI835 integrates both analog input and analog output functions into a single module:
- Input section: Receives 4–20 mA signals from field instruments.
- Output section: Sends 4–20 mA control signals to actuators or control valves.
Each channel is electrically isolated to ensure stable operation and reduce interference in industrial environments.
Operating Sequence
- Field instrument sends analog signal (4–20 mA).
- Input channels convert signal into digital data.
- Controller processes measurement and control logic.
- Output channels convert digital commands back to 4–20 mA signals.
- Field devices respond to control signals.
Key Features
- Combined analog input and output in one module
- 4 input + 4 output isolated channels
- Standard 4–20 mA industrial signal support
- High-resolution 16-bit conversion
- Excellent electrical isolation
- Stable long-term industrial performance
- Compact modular design
- Flexible process control capability
System Role
The NFAI835 acts as a dual-purpose analog interface module, enabling both monitoring and control within the same hardware unit.
Typical System Architecture
Field Sensors → NFAI835 Module → Controller → Process Logic → NFAI835 Output → Control Valves / Actuators
Industrial Applications
The NFAI835 is widely used in:
- Distributed Control Systems (DCS)
- Process automation systems
- Chemical processing plants
- Oil and gas facilities
- Power generation systems
- Water treatment plants
- Pharmaceutical production
- Compact industrial control panels
- Mixed I/O control applications
Installation Guidelines
- Install in a compatible Yokogawa controller rack
- Ensure correct 24 V DC power supply
- Separate analog wiring from power cables
- Use proper grounding for noise reduction
- Follow channel assignment configuration carefully
- Verify input/output calibration during commissioning
Compatible Components
The NFAI835 is compatible with:
- Yokogawa controllers
- Field transmitters (4–20 mA)
- Control valves and actuators
- Variable Frequency Drives (VFDs)
- Industrial process instrumentation
- I/O base units and system backplanes
Alternative Models
| Model |
Description |
| NFAI143 |
Analog Input Module |
| NFAI543 |
Analog Output Module |
| NFAI135 |
Pulse Input Module |
| ADV151 |
Digital Input Module |
| ADV551 |
Digital Output Module |
| AAI835 |
Alternative analog I/O module series |
Advantages
- Combines input and output functions in one module
- Reduces system hardware requirements
- High accuracy signal processing
- Strong electrical isolation design
- Reliable industrial operation
- Space-saving modular architecture
- Suitable for compact automation systems
Frequently Asked Questions
What is the NFAI835 used for?
It is used for both reading analog signals from field instruments and outputting control signals to field devices.
How many channels does it have?
It provides 4 analog inputs and 4 analog outputs.
What signal type does it support?
It supports the standard 4–20 mA DC analog signal.
Can it handle both monitoring and control?
Yes. It is a combined input/output module for simultaneous process measurement and control.
Where is it used?
It is commonly used in DCS systems, process automation, and industrial control applications requiring compact mixed I/O functionality.
Conclusion
The Yokogawa NFAI835 Analog Input/Output Module is a compact and efficient 4-in/4-out isolated analog I/O module designed for industrial automation systems. With high-precision signal conversion, electrical isolation, and dual-function capability, it provides a reliable solution for integrated process monitoring and control applications.