PXI-6528 48-Channel Isolated Industrial Digital I/O Module
The PXI-6528 is a 48-channel industrial digital I/O module that provides 24 optically isolated digital inputs and 24 channel-to-channel isolated solid-state relay outputs. It is designed for monitoring and controlling industrial sensors, switches, relays, indicators and actuators from a PXI automated test system.
Each digital I/O channel has an independent reference and supports signals up to 60 VDC. Programmable power-up states, digital output watchdogs, change detection and software-selectable input filters help the PXI-6528 operate reliably in industrial control, automotive test, aerospace validation and production automation applications.
Key Features of the PXI-6528
- 48 total industrial digital I/O channels
- 24 channel-to-channel isolated digital inputs
- 24 channel-to-channel isolated solid-state relay outputs
- Sink or source input compatibility
- Sink or source output switching
- -60 VDC to 60 VDC input range
- 60 VDC maximum output switching voltage
- 30 Vrms maximum AC switching voltage
- 150 mA maximum switching capacity per output
- 60 VDC channel-to-channel isolation
- Normally open Form A solid-state relay outputs
- Programmable power-up output states
- Digital I/O watchdog protection
- Programmable digital input filters
- Change-detection support
- 100-pin keyed female SCSI front connector
- PXI hybrid-slot compatibility
- NI-DAQmx software support
PXI-6528 Technical Specifications
| Product Model | PXI-6528 |
|---|---|
| Part Number | 778543-01 |
| Product Type | Industrial isolated PXI digital I/O module |
| Total Digital I/O Channels | 48 |
| Digital Input Channels | 24 |
| Digital Output Channels | 24 |
| Bidirectional Digital Channels | None |
| Input Architecture | Optically isolated sink/source inputs |
| Output Architecture | Normally open Form A solid-state relays |
| Isolation Type | Channel-to-channel and channel-to-computer isolation |
| Isolation Rating | 60 VDC or 30 Vrms |
| Digital Input Voltage Range | -60 VDC to 60 VDC |
| Input Low Voltage | -60 VDC to 1 VDC |
| Input High Voltage | 3.2 VDC to 60 VDC |
| Maximum Input Current | 3 mA per channel |
| Typical Input Propagation Delay | 65 µs |
| Minimum Pulse Width for Change Detection | 150 µs |
| Programmable Filter Interval | 400 ns to 200 ms |
| Maximum DC Output Switching Voltage | 60 VDC |
| Maximum AC Output Switching Voltage | 30 Vrms, 42 V peak |
| Maximum Output Switching Capacity | 150 mA per channel |
| Maximum Output On-Resistance | 18 Ω |
| Output Capacitance | 50 pF at 50 V |
| Maximum Off-State Leakage Current | 1 µA |
| Maximum Output Set Time | 5 ms |
| Maximum Output Reset Time | 5 ms |
| Default Output Power-On State | Relays open |
| Programmable Power-Up Response Time | 400 ms |
| Front-Panel Connector | 100-pin keyed female SCSI connector |
| Bus Interface | PXI hybrid |
| Module Format | 3U, single-slot PXI module |
| Operating Temperature | 0°C to 55°C |
| Operating Humidity | 10% to 90%, noncondensing |
| Storage Temperature | -20°C to 70°C |
| Software Support | NI-DAQmx |
PXI-6528 Part Number and Accessories
| Item | Part Number | Description |
|---|---|---|
| PXI-6528 | 778543-01 | 24-input, 24-output, channel-to-channel isolated industrial digital I/O module |
| SH100M-100M Flex Cable | 185095-01 | 1 m shielded 100-pin cable assembly |
| R100M-50F-50F Cable | 182762-02 | 2 m ribbon cable converting the 100-pin connection to two 50-pin connectors |
| SCB-100A | 785024-01 | Shielded, noise-rejecting 100-pin screw-terminal connector block |
| CB-50 | 776164-90 | 50-pin I/O connector block with DIN-rail mounting |
| CB-50LP | 777101-01 | Low-cost unshielded 50-pin I/O connector block |
The PXI-6528 uses one 100-pin front-panel connector. The shielded SH100M-100M Flex cable and SCB-100A provide a straightforward connection method for noise-sensitive industrial installations.
When using the R100M-50F-50F cable, two compatible 50-pin connector blocks are required to access all I/O signals. Verify cable length, shielding, terminal-block quantity and field-wiring requirements before ordering.
24 Optically Isolated Digital Inputs
The PXI-6528 provides 24 optically isolated input channels. Each input has its own positive and negative terminals and an independent reference, allowing signals with different ground potentials to be monitored by the same module.
Optical isolation helps prevent industrial field voltages and ground differences from coupling directly into the PXI computer system. The inputs can monitor switches, proximity sensors, limit switches, alarms, relay contacts and controller status signals.
24 Solid-State Relay Outputs
The module provides 24 normally open Form A solid-state relay outputs. Each output has two isolated terminals and can switch either sinking or sourcing circuits within the applicable voltage and current ratings.
Solid-state outputs do not have the mechanical contacts found in conventional relays. This makes them suitable for applications requiring frequent switching, quiet operation and long service life.
Channel-to-Channel Isolation
Each input and output channel is isolated from the other channels, the PXI computer and the available connector power. The isolation barrier supports differences up to 60 VDC or 30 Vrms between applicable terminals.
Channel-to-channel isolation is useful when signals originate from separate power supplies or controllers. It reduces the need to connect every field signal to one shared digital ground.
Isolation does not protect against signals beyond the specified limits. Do not exceed 60 VDC or 42 V peak between isolated terminals or between an I/O channel and the PXI system.
-60 VDC to 60 VDC Input Range
The isolated inputs support signals from -60 VDC to 60 VDC. An input is recognized as low from -60 VDC through 1 VDC and as high from 3.2 VDC through 60 VDC.
This wide input range allows the PXI-6528 to interface with many 5 V, 12 V, 24 V and 48 V industrial control circuits without requiring standard TTL-level signals.
Sink and Source Input Compatibility
Because each input has two isolated terminals, the module can monitor sinking or sourcing field devices. The wiring polarity and external supply arrangement determine how current flows through the input optocoupler.
Review the connected sensor’s output type before wiring. PNP sensors normally source current, while NPN sensors generally sink current. The PXI-6528 connection should be configured to complete the correct current path.
MOSFET-Based Input Current Limiting
The input circuitry limits current as the applied voltage changes. Typical input current is approximately 1.5 mA at 5 V and approximately 2 mA at 60 V, while the specified maximum input current is 3 mA per channel.
This current-limiting design reduces power dissipation across the wide input-voltage range. Voltage spikes above the 60 V rating can damage the protection circuitry and should be controlled with proper industrial transient protection.
60 V Solid-State Output Switching
Each output can switch as much as 60 VDC or 30 Vrms. The maximum switching capacity is 150 mA per channel, subject to system cooling and total module power dissipation.
The output acts as an isolated electronic contact and does not generate the field voltage itself. An external supply is required to power the connected indicator, relay, actuator or other load.
Normally Open Form A Outputs
The solid-state outputs use a normally open Form A configuration. In the open state, current flow through the output path is interrupted. When commanded on, the solid-state relay closes the isolated circuit.
The default power-on state is open. Programmable power-up functionality can then apply the configured output states after the device initializes.
Output On-Resistance and Voltage Drop
Maximum output on-resistance is 18 Ω. The resulting voltage drop depends on the current flowing through the channel and should be included when evaluating the voltage available to the load.
The module is intended for low-current industrial control signals. It should not be used to directly operate loads requiring more than 150 mA or loads that cannot tolerate the output-path voltage drop.
Programmable Power-Up States
Programmable power-up states allow software to define the initial condition of each digital output. This helps prevent connected actuators from entering an unintended state while the computer and test application are starting.
Output wiring and power-up configuration should be designed so the default open state and the programmed state both provide acceptable system behavior.
Digital I/O Watchdog
The PXI-6528 includes a digital output watchdog. If the application or computer stops responding, the watchdog can place outputs into previously configured safe states.
This feature is useful for systems controlling actuators, alarms, interlocks and other equipment that should not remain indefinitely in its last commanded condition after a software failure.
A watchdog is not a replacement for an independently designed emergency-stop or safety-rated control circuit. Safety-critical protection should not depend solely on software or one PXI module.
Programmable Digital Input Filtering
Digital filtering helps reject electrical glitches, contact bounce and short transient pulses. The filter interval can be configured from 400 ns to 200 ms, and filtering can be enabled on the required input channels.
All filtered inputs share the same programmed interval. Select a duration long enough to reject noise but short enough to detect valid state changes within the required response time.
Switch and Relay Debouncing
Mechanical switches and relay contacts can change state several times briefly before settling. Without filtering, these transitions may be interpreted as multiple input events.
The programmable input filter can debounce these signals in hardware. This reduces the amount of additional filtering required in the host application.
Digital Change Detection
Change detection allows the module to identify transitions on selected input channels. The host application can respond to a change instead of repeatedly polling every digital input.
This capability is useful for alarms, interlocks and event-driven monitoring. The specified minimum pulse width for reliable change detection should be considered when monitoring short-duration signals.
Inductive Load Protection
Relays, solenoids and other inductive loads can generate a high reverse voltage when switched off. This flyback voltage may damage the solid-state output or connected power supply.
Install a flyback diode across compatible DC inductive loads. Other loads may require a snubber, transient-voltage suppressor or manufacturer-recommended suppression circuit.
Typical PXI-6528 Applications
- Industrial automation and monitoring
- Production functional testing
- Automotive controller validation
- Aerospace equipment testing
- PLC signal monitoring
- Proximity and limit-switch acquisition
- Alarm and interlock monitoring
- Relay and indicator control
- Low-current actuator switching
- Manufacturing fixture control
- Hardware-in-the-loop testing
- Environmental chamber control
- Equipment status monitoring
- Isolated logic-level conversion
Industrial Sensor Monitoring
The PXI-6528 can monitor discrete industrial sensors operating from different supply voltages and ground references. Typical devices include proximity sensors, pressure switches, level switches and machine-status contacts.
Confirm whether each sensor uses a PNP, NPN, dry-contact or other output configuration, then wire the isolated input terminals accordingly.
PLC Signal Interfacing
The module can exchange discrete signals with programmable logic controllers. Its wide voltage range and channel-to-channel isolation make it suitable for many 24 V industrial control systems.
Verify the PLC input and output electrical requirements, including logic thresholds, current demand and common wiring. The PXI-6528 should not be connected to circuits exceeding its voltage or current limits.
Automotive Controller Testing
Automotive test systems can use the isolated inputs to monitor controller status signals and the solid-state outputs to apply discrete commands. Individual channel references help accommodate separate electrical domains in the test fixture.
The module can be combined with CAN interfaces, data acquisition hardware and fault insertion units in a PXI hardware-in-the-loop system.
Production Test Fixtures
The PXI-6528 can control fixture relays, indicators and low-current loads while monitoring switches, interlocks and device-under-test outputs. Programmable power-up states and watchdog protection help establish predictable fixture behavior.
For production systems, document the channel assignments, terminal-block wiring and expected safe states so the fixture can be maintained consistently.
NI-DAQmx Software Support
The PXI-6528 is controlled through the NI-DAQmx driver. NI-DAQmx provides functions for reading inputs, writing outputs, configuring digital filters, enabling change detection and setting power-up or watchdog states.
The driver supports LabVIEW and compatible text-based programming environments. NI Measurement & Automation Explorer can be used to identify the module, inspect device information and test individual channels.
LabVIEW Real-Time Integration
The module can be used in compatible LabVIEW Real-Time PXI systems for deterministic industrial monitoring and control. A real-time application can coordinate isolated digital I/O with analog acquisition, communication interfaces and automated test sequences.
System response time depends on the input optocouplers, filter configuration, output switching time and real-time application loop rate.
PXI Hybrid-Slot Compatibility
The PXI-6528 uses a PXI hybrid-compatible bus connector and occupies one 3U chassis slot. Before installation, verify the chassis slot type, controller compatibility, available cooling and NI-DAQmx version.
The PXI chassis should provide adequate airflow, particularly when many outputs carry their maximum current while the inputs are connected to higher voltages.
PXI-6528 Troubleshooting
The PXI-6528 is not detected in NI MAX
Confirm that the module is fully inserted into a compatible PXI or PXI Express hybrid slot. Check chassis power, controller communication and NI-DAQmx installation, then restart the system and rescan the hardware.
An input always reads low
Measure the voltage directly between the positive and negative terminals of that channel. A valid high input must be at least 3.2 VDC. Check sensor polarity, external supply and cable continuity.
An input changes state because of electrical noise
Enable the programmable digital filter and select an interval appropriate for the expected signal. Use shielded cabling and keep field wiring away from motors, contactors and switching power circuits.
A mechanical switch produces several events
Increase the digital filter interval to debounce the contact. Confirm that the selected interval does not delay valid input transitions excessively.
An output does not power the connected load
The solid-state output is an isolated switch and does not generate field power. Confirm that an external supply is connected and that the output, load and supply form a complete current path.
The voltage at the load is too low
Account for the output’s on-resistance and the resistance of cables and connectors. Reduce the load current or use an external interposing relay if the voltage drop is too large.
An output remains open
Check the commanded state, watchdog configuration and programmed safe state. Verify that the connected load does not exceed the 60 V or 150 mA output rating.
The module overheats during operation
Review the number of active outputs, current per channel, input voltages and chassis airflow. High current on many outputs and high voltage on all inputs can increase total module power dissipation.
An inductive load damages an output
Install suitable flyback or transient suppression directly across the load. Do not depend on the PXI-6528 output to absorb inductive switching energy.
The watchdog changes the outputs unexpectedly
Check the configured watchdog timeout, expiration states and application servicing interval. The software must update the watchdog before the selected timeout expires.
PXI-6528 Comparison with Similar Industrial Digital I/O Modules
| Model | Primary Configuration | Best Suited For |
|---|---|---|
| PXI-6528 | 24 isolated inputs and 24 isolated solid-state outputs, 60 V | Balanced high-density isolated monitoring and control |
| PXI-6529 | 48 channel-to-channel isolated inputs | Applications requiring isolated input monitoring only |
| PXI-6525 | 8 isolated inputs, 8 isolated outputs and one counter | Lower-channel-count systems requiring higher output current |
| PXI-6514 | 32 isolated inputs and 32 sourcing outputs | Higher-density bank-isolated sourcing applications |
| PXI-6515 | 32 isolated inputs and 32 sinking outputs | Higher-density bank-isolated sinking applications |
| PCI-6528 | 24 isolated inputs and 24 isolated outputs | Desktop PCI-based industrial control systems |
PXI-6528 vs PXI-6529
The PXI-6528 provides 24 isolated inputs and 24 isolated solid-state outputs. The PXI-6529 provides 48 isolated input channels without the corresponding output bank.
Choose the PXI-6528 when the system must both monitor and control industrial signals. Select the PXI-6529 when all 48 channels are required for isolated input acquisition.
PXI-6528 vs PXI-6525
The PXI-6528 provides a higher channel count with 24 inputs and 24 outputs, but its maximum output switching current is 150 mA. The PXI-6525 provides fewer channels and supports higher-current output switching.
Select the PXI-6528 for high-density industrial monitoring and low-current control. Choose the PXI-6525 when fewer isolated channels, an event counter or greater output capacity is more important.
PXI-6528 vs PXI-6514 and PXI-6515
The PXI-6528 provides channel-to-channel isolation and supports sink or source field wiring. The PXI-6514 and PXI-6515 provide more channels but use bank isolation and dedicated sourcing or sinking output configurations.
Choose the PXI-6528 when independent channel references are required. Select the PXI-6514 or PXI-6515 when higher output density and a shared bank reference are acceptable.
Recommended Related Products
- PXI-6529 48-Channel Isolated Digital Input Module
- PXI-6525 Isolated Digital I/O Module
- PXI-6514 Industrial Sourcing Digital I/O Module
- PXI-6515 Industrial Sinking Digital I/O Module
- PCI-6528 Isolated Industrial Digital I/O Device
- View More NI PXI and PXI Express Modules
Selecting the Right Industrial Digital I/O Module
Choose the PXI-6528 when the application requires 24 isolated inputs, 24 isolated outputs, independent channel references and signals up to 60 VDC. It provides a useful balance between channel density, wiring flexibility and industrial protection features.
Select the PXI-6529 for input-only monitoring, the PXI-6525 for fewer channels with higher-current switching or the PXI-6514 and PXI-6515 when higher channel density is required and bank isolation is acceptable.
Why Choose the PXI-6528?
- Combines 24 industrial inputs and 24 outputs
- Provides channel-to-channel isolation
- Supports signals up to 60 VDC
- Accepts sinking and sourcing field devices
- Uses normally open solid-state relay outputs
- Provides programmable power-up states
- Includes digital watchdog protection
- Offers programmable input filtering and debouncing
- Supports input change detection
- Integrates with NI-DAQmx and LabVIEW
Frequently Asked Questions
What is the PXI-6528?
The PXI-6528 is a 48-channel industrial digital I/O module with 24 isolated inputs and 24 isolated solid-state relay outputs.
What is the PXI-6528 part number?
The standard NI part number for the PXI-6528 is 778543-01.
What input voltage range does it support?
The isolated inputs support signals from -60 VDC to 60 VDC.
What are the input logic thresholds?
Input low is defined from -60 VDC through 1 VDC. Input high is defined from 3.2 VDC through 60 VDC.
What is the maximum output switching voltage?
Each output can switch up to 60 VDC or 30 Vrms, subject to all isolation and operating limits.
What is the maximum output current?
The maximum switching capacity is 150 mA per output channel.
Are the I/O channels individually isolated?
Yes. Each input and output has an independent reference and is isolated from the other channels and the PXI computer.
Does the PXI-6528 use mechanical relays?
No. It uses normally open Form A solid-state relay outputs.
Can the module connect to PNP and NPN sensors?
Yes. Its independently referenced inputs can be wired for compatible sourcing or sinking sensors.
Does it provide programmable input filtering?
Yes. Filter intervals from 400 ns to 200 ms can be used to reject glitches and debounce mechanical contacts.
Does the PXI-6528 support change detection?
Yes. Change detection can notify the application when selected digital inputs change state.
What happens to the outputs if the application fails?
The digital watchdog can place the outputs into configured expiration states if the application stops servicing the watchdog.
Does the module supply power to field loads?
No. The isolated solid-state outputs act as switches. The connected load normally requires an appropriate external field supply.
Which terminal block is recommended?
The shielded SCB-100A and SH100M-100M Flex cable provide a recommended connection method. Two CB-50 blocks can also be used with the R100M-50F-50F cable.
Which software controls the PXI-6528?
The PXI-6528 is controlled through NI-DAQmx and can be integrated with LabVIEW, LabVIEW Real-Time and compatible text-based development environments.
Request a Quote for the PXI-6528
Contact us for current availability, lead time and project pricing for the PXI-6528 48-Channel Isolated Industrial Digital I/O Module. We can also help identify compatible SH100 cables, SCB-100A or CB-50 terminal blocks, PXI chassis and related industrial digital I/O modules.
