The NI 9401 is an 8-channel digital input/output (DIO) module designed for use in CompactRIO and NI CompactDAQ systems. It provides 8 bidirectional digital channels that operate at 5 V/TTL logic levels with a 100 ns response time. This module is intended for general-purpose digital interfacing in various applications, including industrial control, automation, and test and measurement.
Function Description:
The NI 9401 offers flexible digital I/O capabilities. Its 8 DIO channels are grouped into two ports: one containing channels 0, 1, 2, and 3, and the other containing channels 4, 5, 6, and 7. Each digital port can be independently configured in software for either input or output. A key characteristic is that all four channels within a given port must share the same line direction (either all input or all output). This allows for efficient interfacing with devices that require grouped digital lines, such as Serial Peripheral Interface (SPI) devices. For SPI communication, specific DIO channels can be assigned roles like SS (Slave Select), SCLK (Serial Clock), MOSI (Master Out Slave In), and MISO (Master In Slave Out). The module also supports connections to various digital devices, including TTL signals, switches, and LEDs, demonstrating its versatility in digital control and sensing applications.
Important Technical Specifications:
- Channels: 8 Digital Input/Output (DIO)
- Logic Level: 5 V/TTL
- Bidirectional: Yes
- Response Time: 100 ns
- Maximum Voltage (Channel-to-COM): ±30 V maximum on one channel at a time, Measurement Category I. This is the maximum voltage that can be applied or output between any channel and COM without damaging the module or other devices.
- Isolation Voltages:
- Channel-to-channel: None
- Channel-to-earth ground (Continuous): 60 VDC, Measurement Category I
- Channel-to-earth ground (Withstand): 1,000 Vrms, verified by a 5 s dielectric withstand test
- Measurement Category I: For measurements performed on circuits not directly connected to the electrical distribution system. It is crucial not to connect the NI 9401 to signals or use it for measurements within Measurement Categories II, III, or IV, which involve MAINS voltage or higher-energy circuits.
- Overcurrent/Short-Circuit Protection: The module incorporates overcurrent protection on its output channels. If an overcurrent condition occurs, all DIO channels are set to high impedance for approximately 280 ms. During this state, the module can accept new line direction configurations and output state data but cannot pass valid input data to the software.
- Operating Temperature (IEC 60068-2-1, IEC 60068-2-2): -40 °C to 70 °C
- Operating Humidity (IEC 60068-2-78): 10% RH to 90% RH, noncondensing
- Pollution Degree: 2
- Maximum Altitude: 2,000 m
- Indoor Use Only: Yes
- Hazardous Locations Suitability: Class I, Division 2, Groups A, B, C, D, T4 hazardous locations; Class I, Zone 2, AEx nA IIC T4 and Ex nA IIC T4 hazardous locations; and nonhazardous locations only.
- EMC Compliance: Tested and complies with regulatory requirements and limits for electromagnetic compatibility.
Usage Features:
- Software Configuration: Each digital port (channels 0-3 and 4-7) can be independently configured for input or output through software. However, all four channels within a port must share the same direction.
- SPI Device Connectivity: The module is suitable for connecting Serial Peripheral Interface (SPI) devices, allowing for master-slave communication with external peripherals.
- Digital Device Interfacing: Supports direct connection to various digital components like TTL signals, switches, and LEDs, making it adaptable for a wide range of digital control and monitoring tasks.
- Safety Guidelines: Users must operate the NI 9401 only as described in the documentation to prevent hazards and maintain safety protection. Misuse or damage can compromise safety.
- Hazardous Locations Use: When used in potentially explosive environments (Class I, Division 2, Zone 2), specific guidelines must be followed, including installing the system in an enclosure rated to at least IP54 (IEC/EN 60079-15) and ensuring connected signals are within a capacitance limit of 0.2 µF max. Transient disturbances must not exceed 140% of the rated voltage, and the system should be used in an area of not more than Pollution Degree 2. The enclosure must have a door or cover accessible only by a tool.
- EMC Compliance Requirements: To ensure specified EMC performance, the product must be operated with shielded cables and accessories. A clamp-on ferrite bead (part number 782803-01) must be installed on the cable connecting to the NI 9401, as close to the module as possible, to maintain effectiveness.
- Marine Applications: For marine (shipboard) applications, the product must be installed in a shielded enclosure with shielded and/or filtered power and input/output ports. Precautions are also necessary for measurement probes and cables to achieve desired EMC performance.
Maintenance Features:
- Self-Protection: The built-in overcurrent/short-circuit protection helps prevent damage to the module and other devices in case of output short circuits.
- Repair Policy: If the product is damaged, it should be returned to NI for repair, as unauthorized repairs or modifications can void regulatory compliance and operational authority.
- Documentation: Comprehensive documentation, including datasheets and help files (NI-RIO Help, NI-DAQmx Help, LabVIEW FPGA Help, LabVIEW Help), is available at ni.com/manuals and through software installations to assist with setup, configuration, and troubleshooting.
- Support and Services: National Instruments provides worldwide support through ni.com/support, including troubleshooting resources, email, and phone assistance. Additional services like factory installation, repairs, and extended warranties are available at ni.com/services. Product registration at ni.com/register ensures users receive important updates.
- Calibration: If the product supports calibration, calibration certificates can be obtained from ni.com/calibration.
Need help?
General
To Next Page