PCI-6251 16-Bit Multifunction PCI DAQ Device
The NI PCI-6251 is an M Series multifunction data acquisition device that combines high-speed analog input, analog output, digital I/O and counter/timer functions on one conventional PCI board.
It provides 16 single-ended or eight differential analog input channels with 16-bit resolution, a maximum single-channel sampling rate of 1.25 MS/s and a multichannel aggregate rate of 1 MS/s.
Two 16-bit analog outputs allow the PCI-6251 to generate control voltages and stimulus signals. The board also provides 24 digital I/O lines and two 32-bit counter/timers.
Key Features of the PCI-6251
- 16 single-ended or eight differential analog inputs
- 16-bit analog input resolution
- 1.25 MS/s maximum single-channel sampling
- 1 MS/s maximum multichannel aggregate sampling
- Two 16-bit analog output channels
- Up to 2.86 MS/s analog output update rate
- 24 bidirectional digital I/O lines
- Eight hardware-timed digital lines
- Two 32-bit counter/timers
- Analog and digital triggering
- One 68-pin VHDCI connector
- NI-DAQmx software support
PCI-6251 Technical Specifications
| Product Model | PCI-6251 |
|---|---|
| Part Number | 779070-01 |
| Bus Interface | Conventional PCI |
| Analog Inputs | 16 single-ended or 8 differential |
| Input Resolution | 16 bits |
| Single-Channel AI Rate | 1.25 MS/s maximum |
| Multichannel AI Rate | 1 MS/s aggregate maximum |
| Input Ranges | ±0.1 V to ±10 V |
| Analog Outputs | 2 |
| Output Resolution | 16 bits |
| Maximum AO Update Rate | Up to 2.86 MS/s, configuration dependent |
| Output Range | ±10 V, ±5 V or external reference |
| Digital I/O | 24 bidirectional lines |
| Hardware-Timed DIO | 8 lines, up to 10 MHz |
| Counter/Timers | 2 × 32-bit |
| Front Connector | 1 × 68-pin VHDCI |
| Driver | NI-DAQmx |
PCI-6251 Part Number and Accessories
| Item | Part Number | Description |
|---|---|---|
| PCI-6251 | 779070-01 | 16-input, two-output PCI multifunction DAQ device |
| SHC68-68-EPM | 192061-02 | 2 m shielded VHDCI cable |
| SCB-68A | 782536-01 | Shielded screw-terminal connector block |
| BNC-2110 | 777643-01 | BNC connectivity for analog and digital signals |
| BNC-2120 | 777960-01 | Desktop BNC accessory for development and education |
Analog Input Performance
The PCI-6251 supports seven bipolar input ranges between ±100 mV and ±10 V. Differential acquisition is recommended for low-level signals or systems exposed to common-mode noise.
The multiplexed architecture shares one ADC across the active channels. Applications requiring simultaneous phase relationships should consider simultaneous-sampling hardware.
Two Analog Outputs
Two 16-bit analog output channels can generate DC control levels, test stimulus and software-defined waveforms. Maximum update rate depends on how many output channels are active.
The analog outputs should not directly drive high-current loads. Use a suitable amplifier or driver when the connected load exceeds the output-current capability.
Digital and Counter Resources
The 24 digital lines provide static monitoring and control, while eight lines support hardware-timed waveform operations. Two counter/timers support frequency, period, encoder, edge-counting and pulse-generation applications.
PCI-6251 Applications
- Automated stimulus-and-response testing
- Production functional testing
- Closed-loop laboratory experiments
- Data acquisition and control
- Sensor measurement
- Analog voltage generation
- Digital fixture control
- Encoder and frequency measurement
Stimulus-and-Response Testing
The analog outputs can apply controlled voltages to a DUT while the analog inputs measure its response. This makes the PCI-6251 useful for component characterization and automated functional testing.
Control Prototyping
Software can acquire sensor feedback and update analog or digital outputs. Application timing, operating-system latency and safety requirements must be considered before using a desktop PCI system for control.
PCI-6251 Installation Workflow
Step 1: Confirm PCI Compatibility
Verify that the computer provides an available conventional PCI slot.
Step 2: Install NI-DAQmx
Select an NI-DAQmx version compatible with the device and operating system.
Step 3: Install the Hardware
Power down the computer, install the board and secure its bracket.
Step 4: Connect the VHDCI Cable
Attach a compatible cable and terminal accessory without applying power to the external circuit.
Step 5: Run NI MAX Tests
Perform a self-test and verify analog input, analog output and digital operation.
Step 6: Validate the Application
Configure channel ranges, timing, triggering and safe analog output states before connecting the DUT.
PCI-6251 Troubleshooting
The analog output remains at zero
Verify the physical channel, output range, task state and terminal wiring. Confirm that another task has not reserved the output resource.
The acquired signal contains noise
Use shielded differential wiring and review grounding, source impedance and nearby interference sources.
The generated waveform is distorted
Check the requested update rate, load impedance, output-current requirements and waveform scaling.
The device is missing from NI MAX
Check the PCI slot, board seating, NI-DAQmx version and operating-system compatibility.
Digital timing is inconsistent
Use hardware-timed Port 0 lines instead of software-controlled digital updates when deterministic timing is required.
PCI-6251 Comparison
| Model | AI | AO | DIO | Interface |
|---|---|---|---|---|
| PCI-6250 | 16 | 0 | 24 | PCI |
| PCI-6251 | 16 | 2 | 24 | PCI |
| PCIe-6251 | 16 | 2 | 24 | PCI Express |
| PCIe-6351 | 16 | 2 | 24 | PCI Express |
PCI-6251 vs PCI-6250
Both devices provide the same basic analog input, digital I/O and counter configuration. The PCI-6251 adds two analog outputs, while the PCI-6250 is intended for input-focused applications.
Why Choose the PCI-6251?
The PCI-6251 offers a balanced combination of high-speed measurement, analog stimulus, digital control and counter functionality for legacy PCI test systems.
PCI-6251 Frequently Asked Questions
What is the PCI-6251 part number?
The standard orderable part number is 779070-01.
How many analog outputs are included?
The PCI-6251 provides two 16-bit analog outputs.
What is the analog input sample rate?
It supports up to 1.25 MS/s for one channel and 1 MS/s aggregate for multichannel acquisition.
Does it support differential inputs?
Yes. It can be configured for eight differential analog input channels.
Which replacement should be considered?
The PCIe-6351 is a relevant PCI Express alternative, subject to software and connector verification.
Recommended Related Products
- PCI-6250 Multifunction DAQ Device
- PCIe-6251 Multifunction DAQ Device
- PCIe-6351 X Series DAQ Device
- View More NI DAQ Products
Request a Quote for the PCI-6251
Contact us for current availability and pricing for the NI PCI-6251 Multifunction DAQ Device. We can also help select compatible cables, terminal blocks and replacement PCI Express hardware.
