Description

The National Instruments SCXI-1140 is a high-density electromechanical relay output module designed for the SCXI (Signal Conditioning eXtensions for Instrumentation) platform, delivering robust switching capabilities for automated test, data acquisition, and industrial control applications. Each SCXI-1140 provides eight independent channels, with each channel containing four single-pole single-throw (SPST) Form A relays—resulting in a total of 32 relays per module. This architecture enables flexible signal routing, load switching, and power control for devices such as solenoids, indicator lamps, small contactors, and low-power AC/DC circuits. As part of NI’s modular SCXI ecosystem, the NI SCXI-1140 integrates seamlessly with PXI or PCI host controllers via an SCXI chassis, offering deterministic control through NI-DAQmx, LabVIEW, and other standard software environments.

Positioned as a versatile switching solution for medium-duty industrial loads, the National Instruments SCXI-1140 bridges the gap between low-voltage solid-state switches and high-power contactors. Its screw-terminal interface simplifies field wiring, while its electromechanical design ensures compatibility with both AC and DC signals up to 60 VDC or 125 VAC. Although newer PXI-based relay modules offer higher speed, the SCXI-1140 remains widely deployed in legacy aerospace, automotive, and electronics manufacturing test systems where its proven reliability, ease of maintenance, and straightforward channel grouping provide long-term operational value. For facilities managing validated test sequences under strict compliance regimes, the NI SCXI-1140 serves as a drop-in replacement that avoids costly requalification of entire test programs.

NI SCXI-1140

Technical Specifications

Main Features and Advantages

High-density, grouped relay architecture for efficient system design: The NI SCXI-1140 organizes its 32 relays into eight logical channels of four relays each, enabling intuitive mapping to multi-wire devices like 4-wire RTDs, valve banks, or multi-contact sensors. This grouping reduces wiring complexity and simplifies software channel management—particularly useful in functional test systems where multiple signals must be switched in coordination.

Universal AC/DC load compatibility with robust contact ratings: Unlike solid-state relays limited to DC or low-voltage applications, the electromechanical relays in the SCXI-1140 can switch both AC and DC loads up to 125 VAC or 60 VDC, with a 2 A contact rating per relay. This versatility allows direct control of industrial indicators, pilot lights, small heaters, and pneumatic solenoids without external amplifiers—reducing component count and failure points.

Screw-terminal field wiring with rugged mechanical construction: The SCXI-1140 uses a removable 50-pin screw-terminal block (compatible with TB-2640), enabling secure, vibration-resistant connections suitable for factory-floor environments. The terminal block can be pre-wired offline, minimizing system downtime during module replacement—a critical advantage in high-availability test cells.

Seamless integration into SCXI/PXI hybrid architectures: When installed in an SCXI chassis linked to a PXI controller (e.g., via SCXI-1349 or embedded MXI interface), the NI SCXI-1140 appears as a native DAQ device in NI-DAQmx. This allows synchronized operation with analog input modules (e.g., SCXI-1125) or digital I/O cards, enabling closed-loop test sequences such as “energize relay → measure response → log result” within a single software task.

Application Field

In automotive end-of-line testers, the NI SCXI-1140 controls power to multiple vehicle subsystems during validation—such as activating headlight circuits, door lock actuators, and HVAC blower motors—while companion DAQ modules verify current draw and functionality. Its ability to switch both 12 VDC automotive loads and 120 VAC cabin accessories within the same module streamlines test rack design.

Within aerospace avionics burn-in systems, the SCXI-1140 cycles power to navigation units, communication radios, and display modules over extended durations, simulating years of on/off usage in hours. The module’s mechanical relay feedback provides visual and electrical confirmation of switching state—critical for failure analysis during accelerated life testing.

In semiconductor handler interfaces, the NI SCXI-1140 routes power and control signals to device-under-test (DUT) sockets, enabling selective activation of test fixtures based on wafer map data. Its grouped relay channels align naturally with multi-site test configurations, where each group services one DUT slot.

For energy meter calibration labs, the SCXI-1140 switches reference standards into measurement paths or toggles burden resistors during accuracy verification. Because it supports both AC line voltages and DC control logic, the SCXI-1140 eliminates the need for separate AC and DC switching subsystems—reducing cost and footprint.

NI SCXI-1140

Related Products

SCXI-1141: Similar 32-relay module but with latching relays for ultra-low power consumption
SCXI-1142: Reed-relay version for high-speed, low-current signal switching (not for power loads)
TB-2640: Standard 50-pin screw-terminal block accessory for SCXI-1140
PXI-2564: PXI-based 32-channel SPST relay module—modern alternative with faster switching
SCXI-1349: SCXI-to-PXI interface module required for hybrid chassis communication
SCXI-1163: High-power relay module (2.5 A) for heavier industrial loads
PCI-6527: PCI equivalent with mixed isolated inputs and Form C relays
NI 2530: Matrix switch module for complex signal routing (not relay-based)