PCI-6518 32-Channel Isolated Sourcing Digital I/O Device
The PCI-6518 is an industrial PCI digital I/O device designed for factory automation, machine control, process monitoring and automated test systems. It provides 16 optically isolated sink/source digital inputs and 16 optically isolated sourcing digital outputs.
The device accepts input signals from -30 VDC to 30 VDC and switches external field voltages up to 30 VDC. Its isolated architecture helps protect the host computer from field-side noise, ground potential differences and voltage transients commonly encountered in industrial installations.
Programmable power-up states, digital I/O watchdogs, input filtering and NI-DAQmx support make the PCI-6518 suitable for controlling relays, indicators, solenoids and other industrial equipment from a conventional PCI computer.
Key Features of the PCI-6518
- 32 total isolated digital I/O channels
- 16 sink/source digital inputs
- 16 sourcing digital outputs
- Input voltage range from -30 VDC to 30 VDC
- 30 VDC maximum output switching voltage
- Optical isolation between field signals and the PCI bus
- Programmable input filters for noise rejection
- Programmable output power-up states
- Digital I/O watchdog protection
- Self-resetting output-port protection
- 37-pin male D-Sub front connector
- Standard PCI bus interface
- NI-DAQmx driver support
- Compatible with LabVIEW and text-based programming environments
PCI-6518 Technical Specifications
| Product Model | PCI-6518 |
|---|---|
| Part Number | 779084-01 |
| Product Type | Bank-isolated industrial digital I/O device |
| Total Digital Channels | 32 |
| Digital Inputs | 16 sink/source inputs |
| Digital Outputs | 16 sourcing outputs |
| Bidirectional Channels | 0 |
| Input Voltage Range | -30 VDC to 30 VDC |
| Maximum Input Voltage | 30 VDC |
| Input Logic Low | 0 V to ±4 VDC |
| Input Logic High | ±11 VDC to ±30 VDC |
| Maximum Input Current | 4.5 mA per line at 11 V; 12.5 mA per line at 30 V |
| Typical Input Propagation Delay | 75 µs |
| Output Type | Sourcing |
| Maximum Output Switching Voltage | 30 VDC |
| Maximum Single-Line Output Current | Up to 350 mA, subject to temperature and loading limits |
| Typical Output Propagation Delay | 80 µs with a 100 Ω load |
| Default Power-On Output State | Off or open |
| Programmable Power-Up State | Logic 0 or logic 1 |
| Isolation | 30 VDC field-to-bus isolation |
| Output Protection | Self-resetting fuse protection by output port |
| Front Connector | 37-pin male D-Sub |
| Bus Interface | PCI |
| Typical +5 V Power Consumption | 250 mA |
| Dimensions | 14.1 cm × 11.4 cm |
| Weight | 70.9 g |
| Operating Temperature | 0°C to 55°C |
| Software Support | NI-DAQmx |
PCI-6518 Part Number and Accessories
| Item | Part Number | Description |
|---|---|---|
| PCI-6518 | 779084-01 | 16-input, 16-sourcing-output isolated PCI digital I/O device |
| SH37F-37M Cable | 778621-02 | 2 m shielded 37-pin female-to-male I/O cable |
| SH37F-37M Cable | 778621-01 | 1 m shielded 37-pin female-to-male I/O cable |
| CB-37F-LP Connector Block | 779353-01 | Unshielded connector block with a 37-pin D-Sub interface |
| CB-37F Horizontal Connector Block | 778673-01 | 37-pin D-Sub horizontal screw-terminal connector block |
| CB-37F Vertical Connector Block | 778672-01 | 37-pin D-Sub vertical screw-terminal connector block |
| SH37F-P-4 Cable | 778620-04 | 4 m shielded 37-pin female-to-pigtail cable for custom wiring |
| TB-37F-37CP | 779185-01 | 37-pin crimp-and-poke connector kit with strain relief |
| TB-37F-37SC | 779184-01 | 37-pin solder-cup connector kit with strain relief |
The recommended standard connection uses an SH37F-37M shielded cable between the PCI-6518 and a compatible 37-pin connector block. Confirm cable length, shielding, terminal style and enclosure requirements before ordering.
16 Isolated Sink/Source Digital Inputs
The PCI-6518 provides 16 optically isolated digital input channels. Each input can detect either polarity, allowing the device to interface with sourcing or sinking industrial sensors when wired with the correct field reference.
The inputs recognize voltages between ±11 VDC and ±30 VDC as a logic-high state. Voltages from 0 V through ±4 VDC are interpreted as logic low. The region between these thresholds is undefined and should not be used as a normal operating level.
This input design is useful for monitoring proximity sensors, limit switches, photoelectric sensors, alarm contacts and industrial controller outputs.
16 Isolated Sourcing Digital Outputs
The PCI-6518 includes 16 sourcing outputs. A sourcing output supplies current from an external field power source to the connected load when the channel is activated.
Typical sourcing loads are connected between the digital output and the field-supply return. The output therefore provides the positive side of the controlled circuit. This arrangement is commonly used with industrial loads designed for PNP or high-side control.
An external field supply is required because the PCI bus does not provide the power used to operate field loads. The field voltage and output current must remain within the PCI-6518 ratings.
Sourcing Output Current Capability
A single output line can provide up to 350 mA under supported operating conditions. The allowable current decreases when several outputs in the same port operate simultaneously or when ambient temperature increases.
| Ambient Temperature | All Eight Lines Active | One Line Active per Port |
|---|---|---|
| 25°C or below | 75 mA per line | 350 mA |
| 35°C or below | 65 mA per line | 350 mA |
| 45°C or below | 55 mA per line | 350 mA |
| 55°C or below | 50 mA per line | 300 mA |
These limits apply to steady-state operation. Loads with substantial inrush current may require an interposing relay, external driver or current-limiting circuit.
30 V Industrial Signal Compatibility
The PCI-6518 supports input and output circuits operating at up to 30 VDC. It is suitable for common 12 V and 24 V industrial control systems as long as voltage transients remain within the specified limits.
The device is intended for safety extra-low-voltage signal circuits. It should not be connected directly to AC mains, high-voltage power circuits or loads exceeding its isolation and switching ratings.
Optical Isolation
Optical isolation separates the field-side digital signals from the PCI bus and host computer. This separation helps reduce problems caused by electrical noise, ground loops and differences between the computer ground and industrial field ground.
Isolation improves system robustness but does not eliminate the need for correct grounding, overvoltage protection and shield termination. Cable routing should keep digital I/O wiring away from motors, contactors and high-current conductors whenever possible.
Programmable Input Filtering
Input filtering can reject short pulses caused by contact bounce, electromagnetic interference or noisy industrial wiring. This helps prevent a brief disturbance from being interpreted as a genuine state change.
The filter setting should be selected according to the application. A longer filter interval provides greater noise immunity but also increases the time required to recognize a valid input transition.
Digital I/O Watchdog
The PCI-6518 includes a digital I/O watchdog that can place outputs into predefined safe states if the application or computer stops responding. This feature is important when digital outputs control equipment that should not remain energized after a software failure.
Safe states should be selected during system design. De-energizing a channel is not always the safest response, so each output should be configured according to the connected machine, load and control process.
Programmable Power-Up States
The device supports programmable output states during computer startup. This allows an application to define whether individual sourcing outputs should initially be on or off instead of relying only on the default open state.
Power-up configuration helps prevent unintended load activation when the computer restarts. External safety circuits should still be used when uncontrolled motion, heat or stored energy could create a hazard.
Output Protection
The output circuitry includes self-resetting protection for each output port. Protection can help limit damage caused by excessive current, but it is not a substitute for properly sized external fuses or current-limited supplies.
If an output stops operating, disconnect the load and check for short circuits, reversed field wiring, excessive current and inadequate cooling. The protective device may recover after the fault is removed and the hardware is allowed to cool.
Typical PCI-6518 Applications
- Factory automation and machine control
- Industrial sensor monitoring
- 24 V proximity and limit-switch inputs
- PNP load and actuator control
- Relay and contactor-coil control
- Indicator and warning-light control
- Solenoid-valve operation
- Process status monitoring
- Automated test equipment
- Production-line fixtures
- Alarm and interlock monitoring
- Legacy PCI system maintenance
Industrial Sensor Monitoring
The sink/source inputs allow the PCI-6518 to monitor many industrial sensors without requiring every device to use the same output polarity. This is valuable when a machine contains a mixture of PNP and NPN sensors.
Input filtering can improve reliability when signals travel through long cables or pass through electrically noisy sections of a machine. Always confirm sensor leakage current and off-state voltage against the PCI-6518 logic thresholds.
Relay and Solenoid Control
The sourcing outputs can operate compatible DC relay coils, small solenoids and indicators. When controlling inductive loads, use an appropriate flyback diode, transient suppressor or snubber to limit the voltage generated when current is interrupted.
High-current loads should be driven through an external relay or solid-state interface. The external device allows the PCI-6518 to control the load without exceeding its per-line or per-port current limits.
Production Test Systems
In production equipment, the PCI-6518 can monitor fixture switches, safety interlocks and device status signals while controlling relays, indicators and pneumatic valves. Its isolated interface helps separate sensitive computer electronics from the electrical environment of the test station.
NI-DAQmx applications can coordinate the digital I/O with data acquisition devices, digital multimeters, power supplies and other test instruments.
NI-DAQmx Software Support
The PCI-6518 is controlled through the NI-DAQmx driver. NI-DAQmx provides functions for configuring digital input and output tasks, reading input states, writing output values and applying supported watchdog and filtering options.
The driver supports LabVIEW, LabWindows/CVI, C, C++, C# and other compatible programming environments. NI Measurement & Automation Explorer can be used to verify device recognition, inspect configuration and test basic channel operation.
PCI Computer Integration
The PCI-6518 installs in a compatible conventional PCI slot. Before purchasing the device, confirm that the target computer includes the required PCI expansion interface, because many newer computers provide PCI Express slots only.
Power down the computer before installing or removing the board. After installation, install a compatible NI-DAQmx version and confirm that the device appears correctly in NI Measurement & Automation Explorer.
PCI-6518 Wiring Considerations
The front panel uses a 37-pin male D-Sub connector. A shielded SH37F-37M cable and compatible connector block provide convenient access to the input, output, field-power and return connections.
All field wiring should be checked against the official pinout before power is applied. Connecting external supply voltage to the wrong terminal can damage the device, the connected load or the computer.
Use wire and terminals rated for the expected current. Shielded wiring is recommended for electromagnetic compatibility, particularly where cables run near motors, inverters, welding equipment or switching power supplies.
PCI-6518 Troubleshooting
The PCI-6518 is not detected in NI MAX
Confirm that the board is fully inserted into a compatible PCI slot. Check computer firmware settings and Device Manager, install a supported NI-DAQmx version and restart the computer before rescanning for hardware.
An input never changes state
Measure the voltage directly between the appropriate input and field-reference terminals. Confirm that the signal reaches at least the logic-high threshold and that the sensor polarity and power supply are wired correctly.
An input remains high when the sensor is off
Check the sensor’s off-state leakage current and residual voltage. A leaking sensor, induced cable voltage or incorrect reference connection may keep the input above its guaranteed logic-low range.
A sourcing output does not energize the load
Verify that an external field supply is connected and that the load returns to the correct field ground. Confirm output polarity, commanded software state and load continuity.
An output switches off during operation
Check the load’s steady-state and inrush current. Excessive port current or elevated ambient temperature can activate the output protection. Remove the fault and allow the protection device to recover.
An inductive load causes unreliable operation
Install appropriate transient suppression across the coil or load. Keep high-current wiring away from input cables and confirm that the field power supply remains stable during switching.
The outputs change when the application stops
Review the watchdog configuration and programmed safe states. Confirm that the application services the watchdog at the required interval and that every critical output has an intentionally selected failure state.
Input transitions are delayed
Check the configured digital-filter interval and include the normal input propagation delay in the timing analysis. Reduce filtering only when the installation provides sufficient noise immunity.
PCI-6518 Comparison with Similar Digital I/O Devices
| Model | Channel Configuration | Output Type | Best Suited For |
|---|---|---|---|
| PCI-6518 | 16 inputs and 16 outputs | Sourcing | Mixed input monitoring and PNP or high-side load control |
| PCI-6519 | 16 inputs and 16 outputs | Sinking | Mixed input monitoring and NPN or low-side load control |
| PCI-6516 | 32 outputs | Sourcing | Applications requiring additional sourcing outputs |
| PCI-6517 | 32 outputs | Sinking | Applications requiring additional sinking outputs |
| PCI-6514 | 32 inputs and 32 outputs | Sourcing | Higher-channel-count mixed digital I/O systems |
| PCI-6515 | 32 inputs and 32 outputs | Sinking | Higher-channel-count systems using low-side control |
PCI-6518 vs PCI-6519
The PCI-6518 and PCI-6519 both provide 16 isolated sink/source inputs and 16 isolated outputs. Their principal difference is the output circuit: the PCI-6518 has sourcing outputs, while the PCI-6519 has sinking outputs.
Choose the PCI-6518 when the output must supply positive field voltage to a load. Choose the PCI-6519 when the output must complete the load circuit by switching its return path to ground.
PCI-6518 vs PCI-6514
The PCI-6518 provides 16 inputs and 16 sourcing outputs through a compact 37-pin connection. The PCI-6514 provides 32 inputs and 32 sourcing outputs and is better suited to systems requiring twice the input and output channel count.
The PCI-6518 is appropriate when 32 total channels are sufficient and a smaller connector system is preferred. The PCI-6514 is a stronger choice for larger machines and test fixtures with more field signals.
Recommended Related Products
- PCI-6519 16-Input 16-Sinking-Output Isolated Digital I/O Device
- PCI-6516 32-Channel Sourcing Digital Output Device
- PCI-6517 32-Channel Sinking Digital Output Device
- PCI-6514 64-Channel Isolated Sourcing Digital I/O Device
- PCI-6515 64-Channel Isolated Sinking Digital I/O Device
- PCI-6513 64-Channel Isolated Digital I/O Device
- View More NI PCI and USB Data Acquisition Products
Selecting the Right Industrial Digital I/O Device
Choose the PCI-6518 when the application requires 16 isolated inputs, 16 sourcing outputs and compatibility with conventional PCI computers. It is especially suitable for monitoring industrial sensors while controlling PNP-compatible or high-side loads.
Select the PCI-6519 when sinking outputs are required. Choose the PCI-6516 or PCI-6517 for output-only applications, or the PCI-6514 and PCI-6515 when additional input and output channels are needed.
Why Choose the PCI-6518?
- Combines industrial inputs and outputs on one PCI board
- Accepts sinking and sourcing input signals
- Provides 16 sourcing outputs for high-side control
- Supports common 12 V and 24 V industrial systems
- Uses optical isolation to protect the host interface
- Offers programmable input filtering
- Supports programmable power-up output states
- Includes a digital watchdog for failure recovery
- Connects through widely available 37-pin accessories
- Integrates with NI-DAQmx and LabVIEW
Frequently Asked Questions
What is the PCI-6518?
The PCI-6518 is a bank-isolated industrial digital I/O board with 16 sink/source inputs and 16 sourcing outputs for conventional PCI computers.
What is the PCI-6518 part number?
The standard NI part number for the PCI-6518 is 779084-01.
How many channels does the PCI-6518 provide?
It provides 32 channels: 16 dedicated digital inputs and 16 dedicated digital outputs. The channels are not bidirectional.
What is a sourcing output?
A sourcing output supplies positive current from an external field power source to the load. The load is normally connected between the output and the field-supply return.
Can the PCI-6518 accept both PNP and NPN sensor signals?
Its isolated inputs support sink/source operation and either input polarity. Correct sensor, field-power and reference wiring is still required.
What is the maximum input voltage?
The maximum supported input voltage is 30 VDC. The input range extends from -30 VDC to 30 VDC.
What is the maximum output voltage?
The maximum output switching voltage is 30 VDC.
What is the output current rating?
A single output can provide up to 350 mA under supported conditions. When multiple outputs are active, the allowable current per line depends on ambient temperature and total port loading.
Does the PCI-6518 require an external power supply?
Yes. An external field supply is required to power the sourcing output circuits and connected loads.
Does the PCI-6518 support watchdog protection?
Yes. Its digital I/O watchdog can move outputs to predefined safe states if the computer or application becomes unresponsive.
Which connector does the PCI-6518 use?
The board uses a 37-pin male D-Sub connector. A 2 m SH37F-37M shielded cable, part number 778621-02, and CB-37F-LP connector block, part number 779353-01, are compatible accessories.
Which software controls the PCI-6518?
The device is supported by NI-DAQmx and can be programmed with LabVIEW, LabWindows/CVI and compatible text-based development environments.
Can the PCI-6518 be installed in a PCI Express slot?
No. It is a conventional PCI device and requires a compatible PCI expansion slot. A PCI Express-only computer requires a different hardware model or a suitable system-level integration solution.
Request a Quote for the PCI-6518
Contact us for current availability, lead time and project pricing for the PCI-6518 32-Channel Isolated Sourcing Digital I/O Device. We can also help identify compatible SH37F cables, CB-37F connector blocks and related NI industrial digital I/O products.
