The NI-9426 is a high-density C Series digital input module designed for CompactRIO and CompactDAQ systems. It provides 32 simultaneously sampled digital input channels compatible with 24 V industrial logic levels, making it suitable for industrial automation, machine monitoring, embedded control, and high-channel-count digital acquisition systems.
The module is optimized for:
- Industrial switch monitoring
- PLC signal acquisition
- Sensor status monitoring
- FPGA-based deterministic systems
- Embedded automation
- Machine feedback acquisition
- Distributed industrial systems
- Factory automation
Unlike the NI-9425, which uses sinking inputs, the NI-9426 uses a sourcing digital input architecture, making it ideal for industrial systems using sinking-output devices.
Digital Input Architecture
The NI-9426 provides:
- 32 digital input channels
- 24 V industrial logic compatibility
- Sourcing digital input architecture
- 7 μs maximum update time
- Simultaneous channel sampling
- High-density 37-pin DSUB connectivity
Key specifications include:
| Specification | Value |
|---|---|
| Channels | 32 digital inputs |
| Logic level | 24 V industrial |
| Input type | Sourcing |
| Update time | 7 μs maximum |
| Connector | 37-pin DSUB |
| Input impedance | 30 kΩ ±5% |
The module supports direct connection to:
- Industrial switches
- PLC outputs
- Industrial transducers
- Relay outputs
- Industrial sensors
- Machine status signals
- Sinking-output field devices
Sourcing Digital Input Operation
The NI-9426 uses a sourcing digital input architecture.
In this configuration, the module sources current to the external field device, while the connected device sinks current to ground.
This architecture is commonly used with:
- NPN sensors
- Sinking PLC outputs
- Industrial transistor outputs
- Open-collector industrial devices
Digital logic thresholds include:
| State | Input Voltage |
|---|---|
| OFF state | ≥ (Vsup – 5 V) |
| ON state | ≤ (Vsup – 10 V) |
The module also includes hysteresis for improved industrial noise immunity.
High-Density Industrial Monitoring
One of the major advantages of the NI-9426 is its 32-channel density.
This allows engineers to monitor a large number of industrial digital signals while minimizing CompactRIO or CompactDAQ slot usage.
Typical applications include:
Machine Status Monitoring
The NI-9426 can acquire dozens of industrial status signals simultaneously.
PLC Integration
The module is commonly used to read sinking-output PLC signals and machine control states.
Factory Automation
The NI-9426 enables centralized monitoring of industrial sensors and control signals.
Embedded FPGA Systems
CompactRIO FPGA systems can use the NI-9426 for deterministic high-speed industrial signal acquisition.
Compared with lower-channel digital input modules, the NI-9426 significantly reduces chassis expansion requirements and wiring complexity.
Fast Digital Acquisition Performance
The NI-9426 supports a 7 μs maximum update/transfer time, enabling deterministic high-speed digital acquisition.
Additional timing specifications include:
| Parameter | Value |
|---|---|
| Hold time | 0 s minimum |
| Setup time | 1 μs minimum |
| Update time | 7 μs maximum |
This performance makes the module suitable for:
- High-speed industrial automation
- Trigger systems
- Embedded FPGA logic
- Event-driven systems
- Deterministic machine monitoring
Compared with conventional PLC digital inputs, the NI-9426 offers much lower latency and faster update performance.
FPGA Integration and Deterministic Processing
When installed in CompactRIO systems, the NI-9426 interfaces directly with FPGA hardware.
Engineers can implement:
- FPGA-based digital logic
- Deterministic machine control
- Real-time automation
- High-speed event capture
- PWM monitoring
- Industrial protocol handling
- Encoder and trigger processing
The CompactRIO FPGA architecture enables deterministic low-latency digital acquisition that is difficult to achieve with PC-based I/O systems.
This architecture is especially useful for:
- Industrial robotics
- Embedded machine control
- Motion systems
- Industrial automation
- Real-time embedded systems
Isolation and Industrial Protection
The NI-9426 includes industrial-grade electrical protection.
Isolation specifications include:
| Isolation Type | Rating |
|---|---|
| Channel-to-earth | 60 VDC CAT I |
| Withstand voltage | 1,000 Vrms |
| Channel-to-channel | None |
Additional protection features include:
- 30 VDC maximum Vsup-to-channel protection
- Reverse-voltage protection
- Industrial EMC robustness
- Improved noise immunity
These protections improve reliability in harsh industrial environments.
Connectivity and Platform Support
The NI-9426 uses an industry-standard 37-pin DSUB connector, enabling compatibility with a wide range of industrial accessories and cable assemblies.
Typical accessories include:
- NI-9933 connector kit
- NI-9923 screw-terminal accessory
- Custom DSUB breakout assemblies
Supported platforms include:
- CompactRIO
- CompactDAQ
- Single-Board RIO
- EtherCAT systems
- R Series expansion chassis
Supported software includes:
- LabVIEW
- LabVIEW FPGA
- NI-DAQmx
- NI-RIO
- C/C++
- Python
- MATLAB
- .NET integration
Rugged Industrial Design
The NI-9426 is designed for industrial deployment.
Industrial specifications include:
- Operating temperature: -40 °C to 70 °C
- Storage temperature: -40 °C to 85 °C
- Random vibration: 5 g RMS
- Shock resistance up to 50 g
- IP40 protection
The module is suitable for:
- Factory automation
- Transportation systems
- Industrial monitoring
- Embedded industrial machines
- Energy infrastructure
- Distributed industrial cabinets
The NI-9426 also supports hazardous-location deployment in certified CompactRIO systems.
Application-Oriented Use Cases
Industrial Sensor Monitoring
The NI-9426 is widely used for monitoring industrial sensor states and machine feedback signals.
PLC and Machine Integration
The module supports direct acquisition of sinking PLC outputs and industrial machine signals.
Embedded FPGA Systems
CompactRIO FPGA systems can use the NI-9426 for deterministic industrial automation and trigger handling.
Factory Automation
The high channel count makes the NI-9426 ideal for centralized industrial digital monitoring systems.
Comparison with Similar Modules
| Model | Main Difference | Typical Use |
|---|---|---|
| NI-9421 | 8-channel DI | General industrial monitoring |
| NI-9423 | High-speed DI | Fast digital acquisition |
| NI-9425 | 32-channel sinking DI | Sourcing-output industrial systems |
| NI-9426 | 32-channel sourcing DI | Sinking-output industrial systems |
| NI-9435 | 250 VAC/DC DI | High-voltage industrial input |
Compared with the NI-9425, the NI-9426 uses sourcing inputs instead of sinking inputs. Compared with the NI-9423, the NI-9426 focuses more on high-density industrial monitoring rather than ultra-high-speed acquisition.
Conclusion
The NI-9426 is a rugged high-density 32-channel industrial digital input module designed for CompactRIO and CompactDAQ systems requiring deterministic 24 V digital signal acquisition.
Its combination of:
- 32 digital input channels
- 24 V industrial logic compatibility
- Sourcing input architecture
- 7 μs update performance
- FPGA integration
- Industrial ruggedness
- High-density DSUB connectivity
makes it an excellent solution for industrial automation, PLC integration, machine monitoring, embedded control systems, and deterministic FPGA-based industrial applications.
