PXI-2568 31-Channel 2 A SPST PXI Relay Module
The PXI-2568 is a general-purpose PXI relay module designed for automated test equipment, load control and programmable signal routing. It provides 31 independent single-pole single-throw Form A relay channels in a compact, single-slot PXI module.
Each channel uses a latching electromechanical armature relay capable of switching or carrying up to 2 A. With 150 V maximum switching voltage, 40 MHz typical bandwidth and low initial path resistance, the PXI-2568 is suitable for controlling heaters, lights, fans, solenoids, electronic loads and instrumentation signals.
Key Features of the PXI-2568
- 31 independent SPST Form A relay channels
- Alternative 15-channel DPST topology
- 2 A maximum switching or carry current per channel
- 150 V maximum channel-to-channel switching voltage
- 150 V maximum channel-to-ground voltage, CAT I
- 60 W or 62.5 VA maximum switching power per channel
- 40 MHz or greater typical bandwidth
- Less than 0.15 Ω initial DC path resistance
- 12 µV or lower typical thermal EMF
- Latching electromechanical armature relays
- 145 cycles/s maximum cycle speed
- 1 ms typical relay operating time
- PXI hardware trigger support
- Onboard relay-count tracking
- Field-replaceable relays
- 62-pin male D-Sub front connector
- NI-SWITCH software support
- NI Switch Executive compatibility
PXI-2568 Technical Specifications
| Product Model | PXI-2568 |
|---|---|
| Part Number | 778572-68 |
| Product Type | General-purpose PXI relay module |
| Default Topology | 31-SPST, Form A |
| Alternative Topology | 15-DPST |
| Number of Relays | 31 |
| Relay Type | Electromechanical armature relay |
| Relay Operation | Latching |
| Maximum Switching Voltage | 150 V channel-to-channel |
| Maximum Channel-to-Ground Voltage | 150 V, CAT I |
| Maximum Switching or Carry Current | 2 A per channel |
| Maximum Switching Power | 60 W or 62.5 VA per channel |
| Minimum Switch Load | 20 mV, 10 mA |
| Initial DC Path Resistance | Less than 0.15 Ω |
| End-of-Life Path Resistance | Greater than 1 Ω |
| Thermal EMF | 12 µV or lower, typical |
| Bandwidth | 40 MHz or greater, typical |
| Maximum Cycle Speed | 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 | 62-pin male D-Sub |
| Module Format | 3U, one-slot PXI/cPCI module |
| Dimensions | 21.6 cm × 2.0 cm × 13.0 cm |
| Weight | 227 g |
| Operating Temperature | 0°C to 55°C |
| Software Support | NI-SWITCH and NI Switch Executive |
PXI-2568 Part Number and Accessories
| Item | Part Number | Description |
|---|---|---|
| PXI-2568 | 778572-68 | 31-channel, 2 A SPST PXI relay module |
| 62-Pin Female-to-Female Shielded D-Sub Cable | 779956-01 | Shielded cable for connecting the PXI-2568 to compatible accessories or fixtures |
| TBX-62 Terminal Block | 779957-01 | 62-pin D-Sub screw-terminal block for field wiring and signal access |
| PXI-2568 Relay Replacement Kit | 779356-01 | Kit containing ten compatible replacement relays |
The PXI-2568 uses a 62-pin male D-Sub front-panel connector. Verify cable length, shielding, terminal-block requirements, current capacity and fixture wiring before ordering accessories.
31-Channel SPST Relay Architecture
The standard PXI-2568 topology provides 31 independent SPST Form A relays. Each channel contains a common connection and a normally open switched connection. Closing a relay creates an electrical path between the corresponding CH and COM terminals.
Because every channel is controlled independently, the module can connect or disconnect multiple signals and loads within the same automated test sequence. The architecture is useful for applications that require a relatively high relay-channel density combined with 2 A current capacity.
15-Channel DPST Configuration
The PXI-2568 can also be configured as a 15-channel DPST switch. Two SPST relays are operated together to switch two related conductors simultaneously.
This configuration is useful for isolated two-wire signals, paired power connections and applications where both sides of a circuit must be connected or disconnected together. One relay remains available outside the 15 paired channels.
SPST Form A Operation
A Form A relay is normally open when it is in its inactive state. Software closes the relay when a connection is required and opens it to disconnect the circuit.
This simple topology supports load control, power distribution, signal isolation and test-point selection. It also allows engineers to create custom switching arrangements through external wiring and software-defined relay combinations.
Latching Electromechanical Relays
The PXI-2568 uses latching electromechanical armature relays. After a relay changes state, it remains in that state without requiring continuous coil power. This reduces steady-state power consumption and internal heat generation.
Latching behavior means relay states should be explicitly initialized when starting a test application. The test program should not assume that every relay automatically returns to an open state after the chassis is powered off and restarted.
2 A Switching and Carry Current
Each PXI-2568 channel can switch or carry up to 2 A. When the ambient temperature is 55°C or lower, all 31 channels can simultaneously carry their maximum specified current under the conditions defined in the official specifications.
The actual permissible load also depends on switching voltage, load type, inrush current, cabling, connector condition and test-fixture construction. The maximum switching power must not exceed 60 W or 62.5 VA per channel.
150 V Maximum Switching Voltage
The module supports up to 150 V between channels and up to 150 V from a channel to ground. The PXI-2568 is rated for Measurement Category I circuits and must not be connected directly to building mains circuits.
When hazardous voltage is present on any channel, safety extra-low-voltage signals should not be connected to other channels on the same module. Proper insulation, grounding, enclosure and operator-protection methods must be included in the complete test system.
40 MHz Typical Bandwidth
The PXI-2568 provides a typical bandwidth of at least 40 MHz with 50 Ω termination. This allows the module to route DC, control, low-frequency and moderate-frequency instrumentation signals.
Complete system bandwidth depends on cable length, terminal blocks, source impedance, load impedance and test-fixture layout. Short signal paths, suitable shielding and correct termination help preserve signal integrity at higher frequencies.
Low Path Resistance
The initial DC path resistance is less than 0.15 Ω. Low resistance reduces voltage drop and power dissipation when the relay carries current.
Path resistance generally remains low through most of the relay’s service life and then increases rapidly near the end of its electrical life. Cable, terminal-block and fixture resistance must also be considered when evaluating the complete signal path.
Low Thermal EMF
The PXI-2568 has a typical thermal EMF of 12 µV or lower. This characteristic helps reduce thermoelectric measurement error when routing low-level DC signals.
For precision measurements, engineers should also control temperature gradients, connector materials, cable construction and airflow. Allowing adequate settling time after relay operation can further improve measurement stability.
Relay Switching Speed
The module supports a maximum cycle speed of 145 cycles per second. Typical relay operating time is 1 ms, with a specified maximum of 3.4 ms.
Some applications require additional settling time after switching. The appropriate delay depends on the connected instrument, signal level, load characteristics and required measurement accuracy.
Relay Life and Maintenance
The electromechanical relays have an expected mechanical life of up to 100 million operations. Electrical life depends on the voltage, current and type of load switched.
For example, switching 30 VDC at 2 A with a resistive load results in a shorter expected electrical life than switching a lower-voltage, lower-current signal. Relay-count tracking helps maintenance teams identify heavily used channels before their resistance increases or switching becomes unreliable.
Field-Replaceable Relays
The relays inside the PXI-2568 are field replaceable by qualified personnel following the appropriate NI service procedure. The compatible NI relay replacement kit, part number 779356-01, contains ten replacement relays.
Relay replacement requires electrostatic-discharge precautions, correct soldering procedures and verification after servicing. If internal repair is not appropriate for the facility, the module should be sent to a qualified service provider.
Inductive Load Protection
Motors, fans, solenoids, contactors and other inductive loads can generate high-voltage transients when their current path is opened. These transients may exceed the PXI-2568 voltage rating, interfere with module operation and reduce relay life.
Use suitable flyback diodes, snubbers, transient-voltage suppressors or other protection components according to the connected load. Protection should be installed close to the source of the transient whenever practical.
PXI Hardware Triggering
The PXI-2568 supports input and output triggers through PXI trigger lines 0 through 7. Hardware triggering allows relay operations and scan sequences to be coordinated with other instruments in the PXI chassis.
Input triggers support a minimum pulse width of 150 ns when digital filtering is enabled. Output-trigger pulse width can be programmed from 1 µs to 62 µs.
Automated Scanning
NI-SWITCH scanning functions allow the PXI-2568 to step through a predefined list of relay connections. This reduces software overhead and improves repeatability in automated test applications.
A scan list can sequentially connect test points to a measurement instrument, operate a group of loads or change fixture configurations. Hardware triggers can coordinate the scan with measurement and stimulus modules.
Typical PXI-2568 Applications
- Automated test equipment
- Production functional testing
- General-purpose signal routing
- Electronic load control
- Heater and lamp switching
- Fan and motor control
- Solenoid and actuator control
- Power-path connection and isolation
- Test-point selection
- Design verification testing
- Environmental and reliability testing
- Laboratory automation
- Industrial controller validation
- Data acquisition signal routing
Automated Test Equipment
In an automated test system, the PXI-2568 can connect sources, measurement instruments and loads to different device-under-test connections. Software-controlled relays eliminate many manual cable changes and support repeatable test sequences.
The 31-channel configuration provides sufficient density for controlling numerous independent circuits while maintaining a 2 A current rating for each channel.
Heater, Light and Fan Control
The PXI-2568 is suitable for controlling heaters, lights and fans used in electronic validation and environmental testing. Individual channels can operate different loads based on time, temperature or measurement results.
Before connecting a load, verify its steady-state current, startup current and transient behavior. Motors, fans and other inductive devices normally require external transient suppression.
Production Functional Testing
Production test fixtures can use the PXI-2568 to select test points, apply power to individual circuits and control fixture components. Relay routes can change automatically according to the product variant or test step.
Relay-count tracking supports preventive maintenance by identifying channels that receive the greatest number of operations in high-volume production environments.
Instrument and Test-Point Selection
The PXI-2568 can connect a measurement instrument to multiple test points through independent relay channels. It can be combined with a PXIe-4080 digital multimeter for automated voltage, current and resistance testing.
For larger systems, the module can work alongside data acquisition devices, programmable power supplies, digital instruments and other NI PXI modules.
NI-SWITCH Software Support
The PXI-2568 is controlled through the NI-SWITCH instrument driver. NI-SWITCH provides functions for initializing the module, opening and closing relays, configuring topologies, creating scan lists and controlling hardware triggers.
The driver supports LabVIEW, LabWindows/CVI and compatible text-based programming environments. Relay states and switching operations can be integrated into larger automated test applications.
NI Switch Executive Integration
NI Switch Executive allows developers to define named routes and route groups instead of controlling physical relay channels directly throughout the test code.
Meaningful route names simplify applications containing multiple relay modules, instruments and test fixtures. Route validation can also help prevent conflicting connections and reduce switching-configuration errors.
PXI Chassis Integration
The PXI-2568 is a single-slot 3U PXI/cPCI module. It can be installed in a compatible PXI or PXI hybrid slot and operated with other PXI measurement and switching instruments.
Before installation, confirm chassis compatibility, slot availability, cooling, controller communication and NI-SWITCH driver support. Turn off the chassis before installing or removing the module.
PXI-2568 Troubleshooting
The PXI-2568 is not detected in NI MAX
Confirm that the module is fully seated in a compatible PXI slot. Check chassis power, controller communication and NI-SWITCH installation. Restart NI Measurement & Automation Explorer and rescan the PXI system if necessary.
A relay does not open or close
Verify that the correct relay or channel name is used in the application. Check the configured topology, route command, cable, terminal block and external fixture wiring.
The relay state is unexpected after restarting the chassis
The PXI-2568 uses latching relays, so the application should explicitly initialize every required relay state. Do not rely on the relays automatically returning to an open state after power removal.
The signal path has excessive resistance
Inspect the D-Sub cable, terminal block, connectors and fixture wiring. Use relay diagnostics and resistance measurements to determine whether the additional resistance is located inside the module or in the external connection system.
A load causes unreliable relay operation
Check the load’s steady-state current, inrush current, switching voltage and inductive characteristics. Confirm that switching power does not exceed 60 W or 62.5 VA and install external transient suppression when required.
The measurement changes after switching
Allow sufficient time for relay operation and signal settling. Check thermal gradients, grounding, shielding, cable movement and source impedance. Separate high-current load wiring from sensitive measurement signals.
The scan sequence is slower than expected
Review the relay settling time, software execution, measurement aperture and device stabilization requirements. The 145 cycles/s specification does not include every measurement and processing delay in the complete test system.
A channel remains closed when it should be open
Send an explicit open command to the relay and verify the selected channel name. If the electrical path remains closed, disconnect the external wiring and test the module separately to identify a fixture short or failed relay.
Relay-count information indicates heavy use
Compare the channel’s switching count with its electrical loading conditions. Consider moving frequently used routes to lower-use channels or replacing the relay before increased path resistance affects production testing.
PXI-2568 Comparison with Similar Relay Modules
| Model | Primary Configuration | Best Suited For |
|---|---|---|
| PXI-2520 | 80-channel SPST, 2 A relay module | Higher-density independent relay switching |
| PXI-2564 | 16-channel SPST, 5 A relay module | Applications requiring higher current per channel |
| PXI-2566 | 16-channel SPDT relay module | Changeover routing between two signal paths |
| PXI-2568 | 31-channel SPST, 2 A, 150 V relay module | Balanced channel density, voltage and current capacity |
| PXI-2569 | 100-channel SPST relay module | Maximum relay-channel density for lower-current signals |
PXI-2568 vs PXI-2564
The PXI-2568 provides 31 SPST channels with a maximum current of 2 A per channel. The PXI-2564 provides fewer channels but supports higher current up to 5 A per channel.
Choose the PXI-2568 when relay density is more important and the connected loads remain within 2 A. Choose the PXI-2564 when the application requires higher current and 16 channels are sufficient.
PXI-2568 vs PXI-2569
The PXI-2568 provides 31 SPST channels with 2 A current and 150 V switching capability. The PXI-2569 provides 100 SPST channels but is intended for lower-current and lower-voltage switching.
Select the PXI-2568 for medium-power loads and circuits requiring higher voltage. Select the PXI-2569 when channel density is the primary requirement and the connected signals remain within its lower electrical ratings.
PXI-2568 vs PXI-2520
Both modules provide general-purpose SPST switching with 2 A current capability. The PXI-2520 offers a higher relay count, while the PXI-2568 provides 31 latching relay channels through a 62-pin D-Sub interface.
The appropriate model depends on the required channel count, connector system, relay behavior, existing fixture wiring and chassis compatibility.
Recommended Related Products
- PXI-2520 High-Density SPST Relay Module
- PXI-2564 16-Channel 5 A SPST Relay Module
- PXI-2566 16-Channel SPDT Relay Module
- PXI-2569 100-Channel SPST Relay Module
- PXIe-4080 Digital Multimeter
- View More NI PXI and PXI Express Modules
Selecting the Right PXI Relay Module
Choose the PXI-2568 when the test system requires 31 independently controlled SPST relays, 2 A switching, voltage up to 150 V and latching relay operation. It provides a practical balance between channel density and medium-power load capacity.
Choose the PXI-2564 for higher-current loads, the PXI-2566 for SPDT changeover routing or the PXI-2569 when the application requires substantially more independent relay channels.
Why Choose the PXI-2568?
- Provides 31 independent SPST Form A relay channels
- Supports an alternative 15-channel DPST topology
- Switches or carries up to 2 A per channel
- Supports voltage up to 150 V
- Provides 40 MHz or greater typical bandwidth
- Uses power-efficient latching relays
- Offers low initial path resistance
- Supports automated scanning and PXI triggers
- Includes relay-count monitoring
- Supports field replacement of worn relays
- Integrates with NI-SWITCH and NI Switch Executive
Frequently Asked Questions
What is the PXI-2568?
The PXI-2568 is a 31-channel general-purpose PXI relay module used for programmable signal routing, automated testing and electrical load control.
What relay topology does the PXI-2568 provide?
The default topology is 31 independent SPST Form A channels. The module can also be configured as 15 DPST channels.
What is the maximum switching current?
Each channel can switch or carry up to 2 A, subject to the voltage, switching-power and load limitations.
What is the maximum switching voltage?
The PXI-2568 supports up to 150 V channel-to-channel and 150 V 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-2568?
The typical bandwidth is at least 40 MHz with 50 Ω termination.
Does the PXI-2568 use latching relays?
Yes. The PXI-2568 uses latching electromechanical armature relays that retain their switched state without continuous coil power.
Can the PXI-2568 control heaters, lights and fans?
Yes. It is suitable for controlling these loads when their current, voltage, switching power and transient behavior remain within the module specifications.
Can the relays be replaced?
Yes. The relays are field replaceable by qualified personnel. NI replacement kit 779356-01 contains ten compatible relays.
Which cable is compatible with the PXI-2568?
The compatible shielded 62-pin female-to-female D-Sub cable has part number 779956-01.
Which terminal block is compatible with the PXI-2568?
The compatible TBX-62 screw-terminal block has part number 779957-01.
Which software controls the PXI-2568?
The module is controlled through NI-SWITCH and can be integrated into named-route applications using NI Switch Executive.
What is the PXI-2568 part number?
The standard NI part number for the PXI-2568 is 778572-68.
Request a Quote for the PXI-2568
Contact us for current availability, lead time and project pricing for the PXI-2568 31-Channel 2 A SPST PXI Relay Module. We can also help identify compatible D-Sub cables, TBX-62 terminal blocks, replacement relays, PXI chassis and related NI switch modules for your automated test system.
