Product Overview
The National Instruments PXI-2570 is a relay module for PXI systems. It provides 40 single pole double throw relay channels in a single PXI slot. The module is part of the NI PXI switch family and is used in automated test systems that must route signals between instruments and multiple test points. The SPDT configuration allows each channel to select between two signal paths, which adds flexibility compared with simple on and off switching.
Relay switching is a fundamental function in automated test because a small number of instruments is shared across many devices under test. A high channel count relay module reduces the number of separate switch boxes and cables in a rack, which improves integration and maintainability. The PXI-2570 is designed to provide dense switching while remaining controllable from the same software environment as other PXI instruments.
SPDT Relay Configuration
Each channel is a single pole double throw relay, which means the common terminal can be connected to either of two throw terminals. This configuration is useful when a test point must be switched between two instruments, two loads, or two measurement conditions. Engineers should confirm the exact channel mapping and connector pinout for the module configuration against the product documentation.
SPDT switching can simplify a test system by reducing the number of relays required for a given routing function. Instead of using two separate single pole single throw relays to select between two paths, one SPDT relay performs the selection. This reduces component count, wiring, and control complexity.
Switching Characteristics
Relay switching involves mechanical contact movement, so settling time and contact life are important design considerations. Test sequences should allow adequate settling time after a relay changes state before a measurement is taken. Contact wear depends on the voltage and current being switched, so the module should be used within its specified switching limits.
For low level measurements, thermal voltages and contact resistance can affect accuracy. Engineers should allow the system to reach thermal equilibrium and should verify measurement performance with representative switching patterns. Where very low level signals are measured, special care in cable selection and shielding is required.
PXI Integration
The PXI-2570 installs in a compatible PXI chassis and communicates with the controller over the PXI backplane. It can be synchronized with DMMs, source measure units, digitizers, and other PXI instruments through trigger lines and timing resources. This allows switching operations to be coordinated with measurement steps in a defined sequence.
The module is supported by NI switch driver software and can be programmed with LabVIEW, LabWindows/CVI, Measurement Studio, and other compatible development environments. Engineers can create switching sequences that connect instruments to different test points, route signals to measurement devices, and isolate channels for fault analysis.
System Design Considerations
When designing a switching system, engineers should consider the number of test points, the signal types being switched, the required isolation, and the expected switching frequency. Higher switching frequency increases contact wear and may require a different switching technology. The PXI-2570 is best suited to applications where moderate switching rates and low power signals are involved.
Wiring practice affects both reliability and measurement quality. Shielded cable, separation of signal and power conductors, and secure connector fastening reduce noise and intermittent faults. Documentation of the channel map, cable design, and test sequence helps maintain the system as it evolves.
Typical Applications
Automated test signal routing between instruments
Selecting between two loads or measurement paths
Production test with multiple test points
Instrument to device under test connection
High channel count switching systems
PXI based automated test racks
The PXI-2570 provides 40 single pole double throw relay channels in a PXI module. Its channel density and PXI integration make it suitable for automated test switching and signal routing applications.
