PXI-2571 66-Channel 1 A SPDT PXI Relay Module
The PXI-2571 is a high-density, general-purpose PXI relay module designed for automated test equipment, signal routing, load selection and electronic validation. It provides 66 independent single-pole double-throw Form C relay channels in a single-slot PXI module.
Each channel includes normally closed, normally open and common terminals, allowing software to route the common connection between two different signal paths. With 1 A switching capacity, 100 V operation and at least 35 MHz typical bandwidth, the PXI-2571 is suitable for switching instrumentation signals, electronic loads and device-under-test connections.
Key Features of the PXI-2571
- 66 independent SPDT Form C relay channels
- Normally closed, normally open and common terminals
- 1 A maximum switching or carry current per channel
- 100 V maximum channel-to-channel switching voltage
- 100 V maximum channel-to-ground voltage, CAT I
- 60 W or 62.5 VA maximum switching power per channel
- 35 MHz or greater typical bandwidth
- Less than 0.5 Ω initial DC path resistance
- 12 µV typical thermal EMF
- Latching electromechanical armature relays
- 1 ms typical relay operating time
- 145 cycles/s scan rate
- All 66 channels can carry maximum current simultaneously
- PXI hardware trigger support
- Onboard relay-count tracking
- Field-replaceable relays
- 200-position LFH front connector
- PXI hybrid-slot compatibility
- NI-SWITCH and NI Switch Executive support
PXI-2571 Technical Specifications
| Product Model | PXI-2571 |
|---|---|
| Part Number | 778572-71 |
| Product Type | High-density general-purpose PXI relay module |
| Number of Channels | 66 |
| Relay Configuration | SPDT, Form C |
| Channel Connections | Normally closed, normally open and common |
| Relay Type | Electromechanical armature relay |
| Relay Operation | Latching |
| Maximum Switching Voltage | 100 V channel-to-channel |
| Maximum Channel-to-Ground Voltage | 100 V, CAT I |
| Maximum Switching or Carry Current | 1 A per channel |
| Maximum Switching Power | 60 W or 62.5 VA per channel |
| Minimum Switch Load | 20 mV, 1 mA |
| Initial DC Path Resistance | Less than 0.5 Ω |
| End-of-Life Path Resistance | 1 Ω or greater |
| Thermal EMF | 12 µV typical |
| Bandwidth | 35 MHz or greater, typical |
| Scan Rate | 145 cycles/s |
| Typical Relay Operate Time | 1 ms |
| Maximum Relay Operate Time | 3.4 ms |
| Mechanical Relay Life | 1 × 108 cycles |
| Input Trigger Sources | PXI trigger lines 0 through 7 |
| Minimum Input Trigger Pulse Width | 150 ns with digital filtering enabled |
| Output Trigger Destinations | PXI trigger lines 0 through 7 |
| Output Trigger Pulse Width | Programmable from 1 µs to 62 µs |
| Front-Panel Connector | 200-position LFH Matrix 50 receptacle |
| Bus Connection | PXI Hybrid |
| Module Format | 3U, one-slot PXI/cPCI module |
| Dimensions | 21.6 cm × 2.0 cm × 13.0 cm |
| Weight | 174 g |
| Operating Temperature | 0°C to 55°C |
| Storage Temperature | -20°C to 70°C |
| Software Support | NI-SWITCH and NI Switch Executive |
PXI-2571 Part Number and Accessories
| Item | Part Number | Description |
|---|---|---|
| PXI-2571 | 778572-71 | 66-channel, 1 A SPDT PXI relay module |
| LFH200 to 4 × 50-Pin D-Sub Cable | 779038-02 | CH-COM twisted cable for connecting the module to four 50-pin D-Sub interfaces |
| LFH to Bare-Wire Switch Cable | 779038-01 | Bare-wire cable for custom fixtures and direct wiring |
| IM42PNS Relay Replacement Kit | 781678-01 | Through-hole replacement relay kit for PXI-2571 servicing |
The PXI-2571 uses a high-density 200-position LFH connector. Verify cable type, terminal-block requirements, shielding, current capacity and test-fixture wiring before ordering accessories.
66-Channel SPDT Relay Architecture
The PXI-2571 provides 66 independently controlled SPDT relays. Each channel contains a common terminal, a normally closed terminal and a normally open terminal.
Software can connect the common terminal to either of the two available throws. This changeover architecture allows each channel to select between two sources, loads, instruments or device-under-test connections.
With 66 independent channels in one PXI slot, the module is suitable for test systems requiring high relay density without occupying multiple chassis slots.
SPDT Form C Operation
An SPDT Form C relay routes one common connection between a normally closed path and a normally open path. This provides more routing flexibility than an SPST relay, which can only open or close a single signal path.
The PXI-2571 can use this configuration to select between two signals, switch between a test source and a measurement instrument, or change a device-under-test connection between normal and simulated operating conditions.
Normally Closed and Normally Open Paths
Every PXI-2571 channel exposes NC, NO and COM terminals. The normally closed path is connected to common in its default diagram state, while relay operation transfers common to the normally open path.
The test application should explicitly configure the required state of each channel during initialization. This is especially important because the module uses latching relays that can retain their previous state.
Latching Electromechanical Relays
The PXI-2571 uses latching electromechanical armature relays. Once a relay changes position, it does not require continuous coil power to maintain that state.
Latching operation reduces steady-state power consumption and internal heat generation. It also means the software should define all required relay states whenever a test system starts or changes configuration.
Electromechanical contacts provide galvanic isolation and can route AC or DC signals without the semiconductor leakage associated with solid-state switches.
1 A Switching and Carry Current
Each relay channel can switch or carry up to 1 A. Under the operating conditions stated by NI, all 66 channels can simultaneously carry the maximum specified current at ambient temperatures up to 55°C.
The maximum current rating must be considered together with the switching voltage and switching-power limits. Load type, startup current, cable resistance and connector condition can also affect permissible operation.
100 V Switching Capability
The PXI-2571 supports a maximum switching voltage of 100 V between channels and 100 V from a channel to ground. The module is intended for Measurement Category I signal circuits.
It must not be connected directly to building mains circuits or used for CAT II, CAT III or CAT IV measurements. Appropriate insulation, grounding, fusing and fixture protection must be included when hazardous voltages are present.
60 W Maximum Switching Power
The maximum switching power is 60 W or 62.5 VA per channel. Both current and voltage must remain within their individual limits while the total switched power remains below the specified maximum.
For example, a circuit operating at the maximum voltage cannot automatically be switched at the maximum current if doing so would exceed the permissible switching power.
35 MHz Typical Bandwidth
The PXI-2571 provides typical bandwidth of at least 35 MHz with 50 Ω termination. This supports routing of DC, low-frequency and moderate-frequency instrumentation signals.
Actual system bandwidth depends on cable length, terminal blocks, source impedance, load impedance, fixture layout and the number of relay connections in the signal path.
Channel Isolation and Crosstalk
The module is designed to provide electrical isolation between open relay paths and adjacent channels. Typical open-channel isolation is at least 80 dB at 10 kHz and at least 20 dB at 10 MHz with 50 Ω termination.
Typical channel-to-channel crosstalk is 80 dB or better at 10 kHz and 30 dB or better at 10 MHz. Signal frequency, cabling and fixture layout affect complete system performance.
Separating sensitive analog signals from high-current or rapidly changing signals can help reduce interference in practical test installations.
Low Path Resistance
The initial DC path resistance is less than 0.5 Ω. Low resistance helps minimize voltage drop and measurement error through the closed relay connection.
The complete path resistance also includes cables, connectors, terminal blocks and fixture wiring. Resistance normally remains relatively low during most of the relay’s service life and increases rapidly as the relay reaches the end of its electrical life.
Low Thermal EMF
The typical thermal EMF is 12 µV. This characteristic helps reduce thermoelectric errors when routing low-level DC signals and precision measurements.
For demanding applications, temperature gradients, connector materials, cable construction and settling time should also be controlled because each can contribute additional measurement uncertainty.
Relay Switching Speed
The typical relay operating time is 1 ms, with a specified maximum of 3.4 ms. The PXI-2571 also supports a scan rate of up to 145 cycles per second.
Some applications require additional settling time after switching. The final test rate depends on relay operation, instrument aperture, signal stabilization, device-under-test response and software processing.
Expected Relay Life
The mechanical relay life is rated at up to 100 million operations. Electrical life depends on the switched voltage, current and load type.
For a 10 VDC, 100 mA resistive load, expected electrical life is approximately 2.5 million cycles. Heavier loads shorten electrical life, particularly when switching at higher voltage or current.
Onboard relay-count tracking can help maintenance teams identify heavily used channels and schedule replacement before contact resistance affects testing.
Field-Replaceable Relays
The PXI-2571 relays can be replaced by qualified personnel using the appropriate service procedure. The compatible IM42PNS through-hole relay replacement kit has part number 781678-01.
Relay replacement requires electrostatic-discharge precautions, suitable soldering equipment and functional verification after servicing. The module can also be returned to a qualified service provider when internal repair is not appropriate.
Inductive Load Protection
Motors, solenoids, contactors and other inductive loads can generate high-voltage transients when their current path is interrupted. These transients may exceed the relay voltage rating and reduce relay life.
Use flyback diodes, snubbers, transient-voltage suppressors or other suitable protective components according to the load and circuit polarity.
PXI Hardware Triggering
The PXI-2571 accepts input triggers from PXI trigger lines 0 through 7. With digital filtering enabled, the minimum input-trigger pulse width is 150 ns.
Output triggers can also be routed to PXI trigger lines 0 through 7, with programmable pulse width from 1 µs to 62 µs. Hardware triggering allows switching operations to be coordinated with PXI measurement and stimulus instruments.
Automated Relay Scanning
NI-SWITCH scanning functions allow the PXI-2571 to step through a predefined sequence of relay connections. This reduces software overhead and improves repeatability in automated test applications.
Scan lists can select multiple test points, instruments or loads in a programmed order. Hardware triggers can synchronize each connection with measurement acquisition or stimulus generation.
Typical PXI-2571 Applications
- Automated test equipment
- Production functional testing
- High-density signal routing
- Instrument selection
- Test-point selection
- Source and load selection
- Electronic device validation
- Data acquisition signal routing
- Design verification testing
- Reliability and environmental testing
- Laboratory automation
- Industrial controller testing
- Communication and control-signal routing
- Device-under-test interface switching
Automated Test Equipment
The PXI-2571 can connect measurement instruments, signal sources and loads to different device-under-test connections during an automated sequence. Its high channel count helps reduce the number of switch modules required in large ATE systems.
SPDT relays allow each common terminal to select between two different test resources or signal paths without external changeover relays.
Production Functional Testing
Production fixtures can use the module to route test signals according to the product model or test step. Software can change connections automatically without manual cable changes.
Relay-count information can support preventive maintenance by identifying channels with unusually high switching activity in high-volume production systems.
Instrument Selection
An SPDT relay can select between two instruments or connect a device-under-test point to either a stimulus source or measurement input. This supports flexible test configurations using a limited number of instruments.
The PXI-2571 can be combined with a PXIe-4080 digital multimeter for automated voltage, current and resistance measurements across multiple test points.
Source and Load Selection
The common terminal can be switched between two voltage sources, loads or reference signals. This is useful for evaluating device behavior under different electrical conditions.
Before switching between sources, verify that the routing sequence cannot momentarily connect incompatible supplies or create a short circuit through external wiring.
Test-Point Routing
With 66 channels, the PXI-2571 can route numerous device-under-test points to common test resources. Multiple modules can be installed when an application requires several hundred changeover channels.
Using named routes in NI Switch Executive makes large configurations easier to understand and maintain.
NI-SWITCH Software Support
The PXI-2571 is controlled through the NI-SWITCH instrument driver. NI-SWITCH provides functions for initializing the module, changing relay states, defining routes, creating scan lists, configuring triggers and monitoring relay operation.
The driver supports LabVIEW, LabWindows/CVI and compatible text-based programming environments. It can also be integrated into NI TestStand automated test sequences.
NI Switch Executive Integration
NI Switch Executive allows engineers to define named routes and route groups instead of controlling each physical relay directly in application code.
For systems containing multiple switching modules, meaningful route names improve readability and reduce configuration errors. Route validation can help prevent conflicting or electrically unsafe connections.
PXI Hybrid-Slot Compatibility
The PXI-2571 uses a PXI hybrid bus connection and occupies one 3U chassis slot. It can operate alongside digital multimeters, data acquisition modules, programmable power supplies, digitizers and other NI PXI modules.
Before installation, verify slot compatibility, chassis cooling, controller communication, cable clearance and the installed NI-SWITCH version.
PXI-2571 Troubleshooting
The PXI-2571 is not detected in NI MAX
Confirm that the module is fully installed in a compatible PXI hybrid slot. Check chassis power, controller communication and NI-SWITCH installation, then restart NI Measurement & Automation Explorer and rescan the system.
A channel does not switch between NC and NO
Verify the channel name and route command used by the application. Check the LFH cable, D-Sub connections and external fixture wiring. Disconnect the external circuit if necessary and test the relay independently.
The relay state is unexpected after starting the system
The PXI-2571 uses latching relays. Configure an explicit initialization sequence that places every required channel into a known state before applying power or stimulus to the device under test.
The signal path has excessive resistance
Inspect the relay path, LFH cable, D-Sub connectors, terminal blocks and fixture wiring. Compare the measured resistance with a known-good channel to determine whether the problem is internal or external.
The measurement changes after relay switching
Allow sufficient settling time after changing relay states. Check thermal gradients, shielding, grounding, source impedance and cable movement. Keep high-current wiring separated from sensitive measurement signals.
An inductive load causes unreliable switching
Check for voltage transients generated when the load is disconnected. Confirm that the circuit remains within the 100 V, 1 A and 60 W limits, and install appropriate transient suppression.
The scan rate is lower than expected
Review instrument aperture, relay settling time, software processing and device-under-test stabilization. The 145 cycles/s rating does not include all delays within a complete measurement sequence.
One route creates a conflict with another route
Review the physical wiring and Switch Executive route definitions. Verify that two sources cannot be connected together and that break-before-make sequencing is used where necessary.
A heavily used relay becomes unreliable
Check the relay count and measure path resistance. If the relay has reached the end of its electrical life, replace it using the compatible relay kit or send the module to a qualified repair provider.
PXI-2571 Comparison with Similar Relay Modules
| Model | Primary Configuration | Best Suited For |
|---|---|---|
| PXI-2522 | 40-channel SPDT, 2 A relay module | Higher-current SPDT switching with moderate channel density |
| PXI-2523 | 26-channel DPDT, 2 A relay module | Switching two related conductors simultaneously |
| PXI-2566 | 16-channel SPDT relay module | Lower-density general-purpose changeover routing |
| PXI-2570 | 40-channel SPDT relay module | SPDT routing with fewer channels and simplified fixture wiring |
| PXI-2571 | 66-channel SPDT, 1 A, 100 V relay module | High-density general-purpose changeover switching |
PXI-2571 vs PXI-2570
The PXI-2571 provides 66 SPDT channels, while the PXI-2570 provides 40 SPDT channels. The PXI-2571 is preferred when higher channel density is required within a single PXI slot.
Select the appropriate model according to channel count, electrical ratings, connector system and existing fixture design.
PXI-2571 vs PXI-2522
Both models use SPDT relay architecture. The PXI-2571 provides 66 channels with a 1 A rating, while the PXI-2522 provides fewer channels but supports higher current up to 2 A.
Choose the PXI-2571 when channel density is the primary requirement. Choose the PXI-2522 when higher current capacity is more important than the number of relay channels.
PXI-2571 vs PXI-2523
The PXI-2571 provides independent SPDT channels, while the PXI-2523 uses DPDT relays that switch two poles together. The PXI-2571 offers greater channel density for single-pole changeover routing.
Select the PXI-2523 when two related conductors must change state simultaneously. Select the PXI-2571 for a larger number of independent changeover connections.
Recommended Related Products
- PXI-2522 SPDT PXI Relay Module
- PXI-2523 26-Channel DPDT Relay Module
- PXI-2566 SPDT PXI Relay Module
- PXI-2570 40-Channel SPDT Relay Module
- PXIe-4080 Digital Multimeter
- View More NI PXI and PXI Express Modules
Selecting the Right PXI Relay Module
Choose the PXI-2571 when the application requires 66 independent SPDT channels, 1 A switching, voltage up to 100 V and high-density changeover routing within one PXI slot.
Choose the PXI-2522 when higher current capacity is required, the PXI-2523 when two poles must be switched together, or the PXI-2570 when 40 SPDT channels are sufficient.
Why Choose the PXI-2571?
- Provides 66 independent SPDT Form C channels
- Offers NC, NO and COM connections for every relay
- Supports 1 A switching or carry current
- Supports voltage up to 100 V
- Provides 35 MHz or greater typical bandwidth
- Uses power-efficient latching relays
- Supports high-density signal routing in one PXI slot
- Provides automated scanning and PXI triggering
- Includes relay-count tracking
- Supports field replacement of worn relays
- Integrates with NI-SWITCH and NI Switch Executive
Frequently Asked Questions
What is the PXI-2571?
The PXI-2571 is a 66-channel SPDT PXI relay module used for high-density signal routing, automated test equipment and electronic load selection.
How many relay channels does the PXI-2571 provide?
The module provides 66 independent SPDT Form C relay channels.
What connections are available on each channel?
Each channel provides normally closed, normally open and common terminals.
What is the maximum switching current?
The PXI-2571 can switch or carry up to 1 A per channel, subject to its voltage and switching-power limits.
What is the maximum switching voltage?
The maximum switching voltage is 100 V channel-to-channel or channel-to-ground for CAT I signal circuits.
What is the maximum switching power?
The maximum switching power is 60 W or 62.5 VA per channel.
What is the bandwidth of the PXI-2571?
The typical bandwidth is at least 35 MHz with 50 Ω termination.
Does the PXI-2571 use latching relays?
Yes. It uses latching electromechanical armature relays.
Can all 66 channels carry 1 A simultaneously?
Yes. NI specifies that all 66 channels can carry the maximum current simultaneously at ambient temperatures up to 55°C under the specified operating conditions.
Which cable is compatible with the PXI-2571?
Compatible NI options include the LFH200 to four 50-pin D-Sub cable, part number 779038-02, and the LFH to bare-wire cable, part number 779038-01.
Can the PXI-2571 relays be replaced?
Yes. The relays are field replaceable by qualified personnel using the IM42PNS relay replacement kit, part number 781678-01.
Which software controls the PXI-2571?
The PXI-2571 is controlled with NI-SWITCH and can be integrated into named-route applications using NI Switch Executive.
What is the PXI-2571 part number?
The standard NI part number for the PXI-2571 is 778572-71.
Request a Quote for the PXI-2571
Contact us for current availability, lead time and project pricing for the PXI-2571 66-Channel 1 A SPDT PXI Relay Module. We can also help identify compatible LFH cables, terminal accessories, relay replacement kits, PXI chassis and related NI switch modules for your automated test system.
