Digital IO Module

Digital NXI I/O modules connect devices under test, sensors, actuators, and safety circuits to automated measurement and test systems. They acquire digital states, generate control signals, and – depending on the selected module – provide functions such as PWM output, pulse counting, and frequency measurement.

The portfolio includes high-speed digital I/O modules with a high channel density as well as modules for higher signal voltages. The NXI-4101, for example, provides 32 digital channels and functions for PWM, counting, and frequency measurement. The NXI-4102 is suitable for digital signals up to 40 V and supports high-speed data acquisition at up to 20 MS/s. Additional relay, multiplexer, and matrix modules enable potential-free switching and flexible routing of measurement and control signals.

The modular NXI architecture allows digital I/O modules to be combined with NXI measurement and control chassis, DAQ and measurement modules, and communication modules. This provides compact and scalable solutions for functional testing, end-of-line testing, hardware-in-the-loop systems, and industrial automated test equipment.

How to Select a Digital NXI I/O Module

Selecting a suitable digital I/O module depends on the signal levels, required channel count, and processing speed. Functions such as PWM generation, pulse counting, frequency measurement, triggering, isolation, and the electrical load capacity of the inputs and outputs should also be considered.

• Input, output, or bidirectional channel: First determine whether digital states only need to be acquired, control signals must be generated, or individual channels must be configurable as either inputs or outputs.
• Signal level and voltage range: Check the logic and control voltages used within the test system. In addition to conventional logic signals, industrial applications may use 12 V or 24 V signals. The NXI-4102 supports digital signals up to 40 V.
• Channel count and channel allocation: Define how many digital signals must be processed simultaneously. Include reserve channels for possible future extensions. The NXI-4101, for example, provides 32 digital channels for compact multi-channel applications.
• Speed and timing resolution: Simple status signals have lower performance requirements than fast pulses, switching signals, or time-critical control sequences. Check the sampling rate, maximum input frequency, response time, and output timing resolution. The NXI-4102 supports high-speed data acquisition at up to 20 MS/s.
• PWM, counter, and frequency functions: Testing fans, motor controllers, encoders, or pulse-width-modulated signals requires dedicated timing functions. Verify whether the module can generate PWM signals, count pulses, and measure frequency or duty cycle.
• Output current and connected load: Digital outputs cannot directly switch every type of load. Compare the permissible output current with the current consumption of relays, actuators, or other connected components. An external driver stage may be required for higher loads.
• Isolation and reference potentials: Check whether the channels must be galvanically isolated from one another or from system ground. Different reference potentials can cause measurement errors or damage, particularly in battery systems, power electronics, and industrial test equipment.
• Semiconductor I/O or relay contact: Semiconductor outputs are suitable for fast and frequent switching operations. Relay modules provide potential-free contacts and can switch different signal types. Multiplexer or matrix modules can additionally be used for flexible signal routing.
• Triggering and synchronization: When digital signals must be evaluated together with analog measurements, the trigger functions and time bases must be coordinated. Combining the I/O modules with NXI DAQ and measurement modules enables time-correlated test sequences.
• Chassis and system performance: Select an NXI chassis with sufficient slots and communication bandwidth. Controller performance and data volume must also be considered for large channel counts or high-speed signals.
• Interfaces and automation: For automated test equipment, verify the command structure, software drivers, remote-control functions, and communication with PLCs, test software, or higher-level control systems. The system can be extended with suitable NXI communication modules.
• Safety and fault conditions: Consider the module behavior during power-up, communication failure, and system faults. Safety-related shutdown functions should be evaluated separately and should not rely exclusively on software-controlled I/O signals.
• Scalability and system integration: ET System can combine digital I/O modules with measurement equipment, power supplies, electronic loads, switching equipment, and safety components through custom test system integration.

To select a suitable configuration, specify the signal voltages, channel count, signal direction, switching frequency, output load, and automation requirements. Contact our technical sales team for support with configuring your NXI system.