16, 32, or 80 analog inputs at 16 bits, 1.25 MS/s (1 MS/s scanning, NI 6255 specified at 750 kS/s scanning) Up to 4 analog outputs at 16 bits, 2.8 MS/s (2 μs full-scale settling) 7 programmable input ranges (±100 mV to ±10 V) per channel Up to 48 TTL/CMOS digital I/O lines (up to 32 hardware-timed at 10 MHz)	Two 32-bit, 80 MHz counter/timers Analog and digital triggering X1, X2, or X4 quadrature encoder inputs 2-year calibration interval

Overview

NI M Series high-speed multifunction data acquisition (DAQ) devices are optimized for superior accuracy at fast sampling rates. These devices have NI-MCal calibration technology for improved measurement accuracy and six DMA channels for high-speed data throughput. They have an onboard NI-PGIA 2 amplifier designed for fast settling times at high scanning rates, ensuring 16-bit accuracy even when measuring all channels at maximum speeds. All high-speed devices have a minimum of 16 analog inputs, 24 digital I/O lines, seven programmable input ranges, analog and digital triggering, two counter/timers, and an extended two-year calibration interval.

NI recommends high-accuracy M Series devices (NI 628x) for 5X more measurement sensitivity or industrial M Series devices (NI 623x) for 60 VDC isolation and superior noise rejection.

See the NI USB-625x data sheet for information specific to USB M Series devices.

Requirements and Compatibility

OS Information Windows 2000/XP Windows Vista x64/x86 Linux® Mac OS X

Driver Information NI-DAQmx NI-DAQmx Base

Software Compatibility ANSI C/C++ LabVIEW LabVIEW SignalExpress Visual Studio .NET LabWindows/CVI

Comparison Tables

Family	Bus	Analog Inputs	AI Resolution (bits)	Analog Outputs	AO Resolution	Max Update Rate (MS/s)	AO Range (V)	Digital I/O	Correlated (clocked) DIO
NI 6250	PCI, PXI	16	16	0	-	-	-	24	8, up to 10 MHz
NI 6251	PCI, PCI Express, PXI, PXI Express, USB	16	16	2	16	2.8	±10, ±5, ±ext ref	24	8, up to 10 MHz
NI 6254	PCI, PXI	32	16	0	-	-	-	48	32, up to 10 MHz
NI 6255	PCI, PXI, USB	80	16	2	16	2.8	±10, ±5, ±ext ref	24	8, up to 10 MHz
NI 6259	PCI, PCI Express, PXI, PXI Express, USB	32	16	4	16	2.8	±10, ±5, ±ext ref	48	32, up to 10 MHz

Application and Technology

M Series for Test

For test, you can use M Series high-speed analog inputs and 10 MHz digital lines with NI signal conditioning for applications including electronics test, component characterization, and sensor measurements. High-speed M Series devices are compatible with NI SCC and SCXI signal conditioning platforms, which provide amplification, filtering, and power for virtually every type of sensor. These platforms also are compliant with IEEE 1451.4 smart transducer electronic data sheet (TEDS) sensors, which provide digital storage for sensor data sheet information.

M Series for Control

M Series digital lines can drive 24 mA for relay and actuator control. By clocking the digital lines as fast as 10 MHz, you can use these lines for pulse-width modulation (PWM) to control valves, motors, fans, lamps, and pumps. With four waveform analog outputs, two 80 MHz counter/timers, and six DMA channels, M Series devices can execute multiple control loops simultaneously. High-speed M Series devices also have direct support for quadrature encoder measurements, protected digital lines, and digital debounce filters for control applications. With up to 80 analog inputs, 32 clocked digital lines, and four analog outputs, you can execute multiple control loops with a single device. For higher-count control loops, you can use M Series devices in conjunction and tightly synchronized with National Instruments analog output devices for 64 or more loops. With the NI SoftMotion Development Module for LabVIEW, you can create a complete custom motion controller with M Series devices.

M Series for Design

You can use the wide range of I/O – from 80 analog inputs to 48 digital lines – to measure and verify prototype designs. M Series devices and NI LabVIEW SignalExpress interactive measurement software deliver benchtop measurements to the PC. With LabVIEW SignalExpress interactive configuration-based steps, you can quickly create design verification tests. The fast acquisition and generation rates of high-speed M Series devices along with LabVIEW SignalExpress provide on-the-fly design analysis. You can convert your tested and verified LabVIEW SignalExpress projects to LabVIEW applications for immediate M Series DAQ use, thus bridging the gap between test, control, and design applications.

M Series Performance on PCI Express

National Instruments was the first company to empower engineers and scientists to use the PCI Express and PXI Express buses for data acquisition. PCI Express M Series boards contain six DMA channels to maximize data throughput without using PC processing time. The PCI Express bus delivers the highest bandwidth compared to any other PC bus, and it eliminates throughput bottlenecks by providing 250 MB/s per-direction bandwidth across the x1 (“by one”) lane for increased data transfer. Each slot allocates dedicated bandwidth, meaning that multiple PCI Express boards do not share bandwidth for data transfer. With this improvement over the shared-bandwidth PCI architecture, all onboard I/O runs simultaneously while data is transferred to and from PC memory across the bus. The PXI Express specifications integrate PCI Express signaling into the PXI Standard, which increases backplane bandwidth from 132 MB/s to 6 GB/s, a 45 times improvement. Both PCI Express and PXI Express facilitate a smooth transition to new hardware by providing complete backward compatibility to software written for applications that use PCI or PXI, respectively.

Hybrid-Slot-Compatible PXI Modules

PXI M Series modules are hybrid-slot-compatible so that you can use them in both PXI slots and the hybrid slots found in new PXI Express chassis. The PXI Systems Alliance specifies that hybrid-slot-compatible PXI modules use modified slot connectors to mechanically fit in both PXI slots and hybrid slots. This mechanical change: 

• Provides compatibility with past, current, and future PXI chassis
• Maintains existing product specifications
• Requires no software changes (application or driver)
• Maintains speed and capability of all PXI communication (PXI Express signaling is not provided)
  

However, hybrid-slot-compatible PXI modules do not include the pins used to implement PXI local bus communication, which is used for backplane SCXI control from the right-most PXI slot in PXI/SCXI combination chassis (PXI-1010, PXI-1011, PXI-1050, and PXI-1052). For these applications, NI provides unmodified PXI M Series modules that maintain the required local bus capabilities. Refer to the SCXI Control of PXI/SCXI Combination Chassis section in the Ordering Information section for part numbers.

Industrial Data Acquisition

When you need performance and accuracy from a data acquisition device in an electrically noisy or harsh environment, consider National Instruments industrial M Series devices (NI 623x). NI industrial DAQ devices offer a set of high-reliability features, including isolation, ±20 mA current I/O, 24 V digital logic levels, and digital debounce filters. Isolation prevents ground loops, rejects high common-mode voltages, and protects users and equipment from high-voltage transients. Four to 20 mA current loops are immune to most sources of electrical noise and voltage (IR) drops along extensive cable lengths. Sourcing or sinking 24 V digital I/O interfaces directly with pumps, valves, relays, and other industry-standard sensors and actuators, and programmable debounce filters remove glitches and spikes from switches and relays connected to digital input lines.

Simultaneous and Intelligent Data Acquisition

When you need to obtain performance from a data acquisition device beyond the capabilities of a multifunction data acquisition device, National Instruments provides simultaneous sampling with NI S Series and intelligent data acquisition with NI R Series. The S Series architecture dedicates an analog-to-digital converter (ADC) per channel to provide higher aggregate sampling rates compared to multiplexed devices. S Series devices are ideal for applications including IF digitization, transient recording, ultrasound and sonar testing, and high-energy physics. R Series multifunction DAQ devices contain a field-programmable gate array (FPGA) that is reconfigurable using the LabVIEW FPGA Module.

They combine analog input, analog output, and digital I/O on a single device. You can customize these devices to develop capabilities such as complete control over the synchronization and timing of all signals and operations; user-defined onboard decision-making logic; and digital lines individually configurable as input, output, counter/timers, PWM, flexible encoder inputs, or user-defined communication protocols.

Recommended Accessories

Signal conditioning is required for sensor measurements or voltage inputs greater than 10 V. NI SCXI is a versatile, high-performance signal conditioning platform optimized for high-channel-count applications. NI SCC provides portable, flexible signal conditioning options on a per-channel basis. Visit ni.com/sigcon for resources on available NI signal conditioning.

Recommended Driver Software

National Instruments measurement services software, built around NI-DAQmx driver software, includes intuitive application programming interfaces, configuration tools, I/O assistants, and other tools designed to reduce system setup, configuration, and development time. National Instruments recommends using the latest version of NI-DAQmx driver software for application development in NI LabVIEW, LabVIEW SignalExpress, LabWindows™/CVI, and Measurement Studio software. To obtain the latest version of NI-DAQmx, visit ni.com/support/daq/versions. NI measurement services software speeds up your development with features including the following:

• A guide to create fast and accurate measurements with no programming using the DAQ Assistant
• Automatic code generation to create your application in LabVIEW; LabWindows/CVI; LabVIEW SignalExpress; and C#, Visual Studio .NET, ANSI C/C++, or Visual Basic using Measurement Studio
• Multithreaded streaming technology for 1,000 times performance improvements
• Automatic timing, triggering, and synchronization routing to make advanced applications easy
• Thousands of free software downloads available at ni.com/zone to jump-start your project
• Software configuration of all digital I/O features without hardware switches/jumpers
• Single programming interface for analog input, analog output, digital I/O, and counters on hundreds of multifunction data acquisition hardware devices 

M Series devices are compatible with the following versions (or later) of NI application software – LabVIEW, LabWindows/CVI, or Measurement Studio versions 7.x; and LabVIEW SignalExpress 2.x.

Ordering Information

For a complete list of accessories, visit the product page on ni.com.

Products	Part Number	Recommended Accessories	Part Number
NI PXI-6259
NI PXI-6259 Each NI PXI-6259 requires: 2 Cables, 2 Connector Blocks	779632-01	Connector 0:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXI-6259 Each NI PXI-6259 requires: 2 Cables, 2 Connector Blocks	779119-01	Connector 0:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXI-6251
NI PXI-6251 Each NI PXI-6251 requires: 1 Cable, 1 Connector Block	779631-01	Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXI-6251 Each NI PXI-6251 requires: 1 Cable, 1 Connector Block	779117-01	Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PCIe-6251
NI PCIe-6251 Each NI PCIe-6251 requires: 1 Cable, 1 Connector Block	779512-01	Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PCI-6254
NI PCI-6254 Each NI PCI-6254 requires: 2 Cables, 2 Connector Blocks	779071-01	Connector 0:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PCI-6251
NI PCI-6251 Each NI PCI-6251 requires: 1 Cable, 1 Connector Block	779070-01	Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXI-6254
NI PXI-6254 Each NI PXI-6254 requires: 2 Cables, 2 Connector Blocks	779118-01	Connector 0:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PCI-6250
NI PCI-6250 Each NI PCI-6250 requires: 1 Cable, 1 Connector Block	779069-01	Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PCI-6255
NI PCI-6255 Each NI PCI-6255 requires: 2 Connector Blocks	779546-01	Connector 0:
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXI-6250
NI PXI-6250 Each NI PXI-6250 requires: 1 Cable, 1 Connector Block	779116-01	Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXI-6255
NI PXI-6255 Each NI PXI-6255 requires: 2 Connector Blocks	779547-01	Connector 0:
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXIe-6259
NI PXIe-6259 Each NI PXIe-6259 requires: 2 Cables, 2 Connector Blocks	779778-01	Connector 0:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PXIe-6251
NI PXIe-6251 Each NI PXIe-6251 requires: 1 Cable, 1 Connector Block	779777-01	Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PCIe-6259
NI PCIe-6259 Each NI PCIe-6259 requires: 2 Cables, 2 Connector Blocks	779513-01	Connector 0:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
NI PCI-6259
NI PCI-6259 Each NI PCI-6259 requires: 2 Cables, 2 Connector Blocks	779072-01	Connector 0:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01
		Connector 1:
		Cable: Shielded - SHC68-68-EPM Cable (2m)       **Also available: Unshielded	192061-02
		Connector Block: Screw Terminals - SCB-68       **Also available: BNC Termination	776844-01

Software Recommendations

NI LabVIEW Professional Development System for Mac OS X	Multiple communication options (TCP/IP, UDP, serial, and more) Source code control integration and code complexity metrics Extensive signal processing, analysis, and math functionality Easy-to-use graphical development environment Tight integration with a wide range of measurement hardware Rapid user interface development for displaying live data	NI Measurement Studio Professional Edition	Requires Microsoft Visual Studio 2008/2005/.NET 2003 or Visual Studio 6.0 Base analysis and instrumentation components for Microsoft Visual Basic, Visual C#, and Visual C++ Scientific user interface controls Acquire data from GPIB, serial, Ethernet, and plug-in data acquisition devices Code-generating DAQ Assistant and Instrument I/O Assistant Cross-platform communication with network variables
NI LabWindows™/CVI for Windows	Simplified cross-platform communication with network variables The mark LabWindows is used under a license from Microsoft Corporation. Measurement Studio .NET tools (included in LabWindows/CVI Full only) Analysis tools for array manipulation, signal processing statistics, and curve fitting Real-time advanced 2D graphs and charts with support for Windows Vista/XP/2000 Complete hardware compatibility with IVI, VISA, DAQ, GPIB, and serial	NI LabVIEW SignalExpress for Windows	Scale your application with automatic LabVIEW code generation Create custom reports or easily export data to LabVIEW, DIAdem or Microsoft Excel Perform basic signal processing, analysis, and file I/O Quickly configure projects without programming Log data from more than 250 data acquisition devices Control over 400 PC-based and stand-alone instruments

Support and Services

System Configuration and Deployment Services

NI system services are designed to save you time and money by having NI technicians assemble, configure, test, and document your NI PXI, CompactRIO, or Compact FieldPoint system before it is shipped from the NI factory. With system services, you can take advantage of an out-of-the-box experience that gets you started with your new system quickly and provides valuable post-deployment services such as an extended warranty. For more information, visit ni.com/systemservices.

Calibration

NI measurement hardware is calibrated to ensure measurement accuracy and verify that the device meets its published specifications. To ensure the ongoing accuracy of your measurement hardware, NI offers basic or detailed recalibration service that provides ongoing ISO 9001 audit compliance and confidence in your measurements. To learn more about NI calibration services or to locate a qualified service center near you, contact your local sales office or visit ni.com/calibration.

Technical Support

Get answers to your technical questions using the following National Instruments resources.

Support - Visit ni.com/support to access the NI KnowledgeBase, example programs, and tutorials or to contact our applications engineers who are located in NI sales offices around the world and speak the local language.
Discussion Forums - Visit forums.ni.com for a diverse set of discussion boards on topics you care about.
Online Community - Visit community.ni.com to find, contribute, or collaborate on customer-contributed technical content with users like you.

Repair

While you may never need your hardware repaired, NI understands that unexpected events may lead to necessary repairs. NI offers repair services performed by highly trained technicians who quickly return your device with the guarantee that it will perform to factory specifications. For more information, visit ni.com/repair.

Training and Certifications

The NI training and certification program delivers the fastest, most certain route to increased proficiency and productivity using NI software and hardware. Training builds the skills to more efficiently develop robust, maintainable applications, while certification validates your knowledge and ability.
Classroom training in cities worldwide - the most comprehensive hands-on training taught by engineers.
On-site training at your facility - an excellent option to train multiple employees at the same time.
Online instructor-led training - lower-cost, remote training if classroom or on-site courses are not possible.
Course kits - lowest-cost, self-paced training that you can use as reference guides.
Training memberships and training credits - to buy now and schedule training later.

Visit ni.com/training for more information.

Extended Warranty

NI offers options for extending the standard product warranty to meet the life-cycle requirements of your project. In addition, because NI understands that your requirements may change, the extended warranty is flexible in length and easily renewed. For more information, visit ni.com/warranty.

OEM

NI offers design-in consulting and product integration assistance if you need NI products for OEM applications. For information about special pricing and services for OEM customers, visit ni.com/oem.

Detailed Specifications

Specifications listed below are typical at 25 °C unless otherwise noted. Refer to the M Series User Manual for more information about NI 625x devices.

Analog Input
Number of channels
NI 6250/6251		8 differential or 16 single ended
NI 6254/6259		16 differential or 32 single ended
NI 6255		40 differential or 80 single ended
ADC resolution		16 bits
DNL		No missing codes guaranteed
INL		Refer to the AI Absolute Accuracy Table
Sampling rate
Maximum
NI 6250/6251/6254/6259		1.25 MS/s single channel, 1.00 MS/s multi-channel (aggregate)
NI 6255		1.25 MS/s single channel 750 kS/s multi-channel (aggregate)
Minimum		No minimum
Timing accuracy		50 ppm of sample rate
Timing resolution		50 ns
Input coupling		DC
Input range		±10 V, ±5 V, ±2 V, ±1 V, ±0.5 V, ±0.2 V, ±0.1 V
Maximum working voltage for analog inputs (signal + common mode)		±11 V of AI GND
CMRR (DC to 60 Hz)		100 dB
Input impedance
Device on
AI+ to AI GND		>10 GΩ in parallel with 100 pF
AI- to AI GND		>10 GΩ in parallel with 100 pF
Device off
AI+ to AI GND		820 Ω
AI- to AI GND		820 Ω
Input bias current		±100 pA
Crosstalk (at 100 kHz)
Adjacent channels		-75 dB
Non-adjacent channels		-90 dB1
Small signal bandwidth (-3 dB)		1.7 MHz
Input FIFO size		4,095 samples
Scan list memory		4,095 entries
Data transfers
PCI/PCIe/PXI/PXIe devices		DMA (scatter-gather), interrupts, programmed I/O
USB devices		USB Signal Stream, programmed I/O
Overvoltage protection (AI <0..79>, AI SENSE, AI SENSE 2)
Device on		±25 V for up to four AI pins
Device off		±15 V for up to four AI pins
Input current during overvoltage condition		±20 mA max/AI pin
1  For USB-6255 devices, channel AI <0..15> crosstalk to channel AI <64..79> is -67 dB; applies to channels with 64-channel separation, for example, AI (x) and AI (x + 64).
Settling Time for Multichannel Measurements
NI 6250/6251/6254/6259 Range ±60 ppm of Step (±4 LSB for Full Scale Step) ±15 ppm of Step (±1 LSB for Full Scale Step) ±10 V, ±5 V, ±2 V, ±1 V 1 µs 1.5 µs ±0.5 V 1.5 µs 2 µs ±0.2 V, ±0.1 V 2 µs 8 µs
NI 6255 Range ±60 ppm of Step (±4 LSB for Full Scale Step) ±15 ppm of Step (±1 LSB for Full Scale Step) ±10 V, ±5 V, ±2 V, ±1 V 1.3 µs 1.6 µs ±0.5 V 1.8 µs 2.5 µs ±0.2 V, ±0.1 V 3 µs 8 µs

Typical Performance Graphs

Analog Triggers
Number of triggers		1
Source
NI 6250/6251		AI <0..15>, APFI 0
NI 6254/6259		AI <0..31>, APFI <0..1>
NI 6255		AI <0..79>, APFI 0
Functions		Start Trigger, Reference Trigger, Pause Trigger, Sample Clock, Convert Clock, Sample Clock Timebase
Source level
AI <0..79>		±full scale
APFI <0..1>		±10 V
Resolution		10 bits, 1 in 1,024
Modes		Analog edge triggering, analog edge triggering with hysteresis, and analog window triggering
Bandwidth (-3 dB)
AI <0..79>		3.4 MHz
APFI <0..1>		3.9 MHz
Accuracy		±1%
APFI <0..1> characteristics
Input impedance		10 kΩ
Coupling		DC
Protection
Power on		±30 V
Power off		±15 V
Analog Output
Number of channels
NI 6250/6254		0
NI 6251/6255		2
NI 6259		4
DAC resolution		16 bits
DNL		±1 LSB
Monotonicity		16 bit guaranteed
Accuracy		Refer to the AO Absolute Accuracy Table
Maximum update rate
1 channel		2.86 MS/s
2 channels		2.00 MS/s
3 channels		1.54 MS/s
4 channels		1.25 MS/s
Timing accuracy		50 ppm of sample rate
Timing resolution		50 ns
Output range		±10 V, ±5 V, ±external reference on APFI <0..1>
Output coupling		DC
Output impedance		0.2 Ω
Output current drive		±5 mA
Overdrive protection		±25 V
Overdrive current		20 mA
Power-on state		±5 mV2
Power-on glitch		1.5 V peak for 1.5 s
Output FIFO size		8,191 samples shared among channels used
Data transfers
PCI/PCIe/PXI/PXIe devices		DMA (scatter-gather), interrupts, programmed I/O
USB devices		USB Signal Stream, programmed I/O
AO waveform modes: Non-periodic waveform Periodic waveform regeneration mode from onboard FIFO Periodic waveform regeneration from host buffer including dynamic update
Settling time, full scale step 15 ppm (1 LSB)		2 µs
Slew rate		20 V/µs
Glitch energy at midscale transition, ±10 V range
Magnitude		10 mV
Duration		1 µs
2  For all USB-6251/6259 Screw Terminal devices, when powered on, the analog output signal is not defined until after USB configuration is complete.
External Reference
APFI <0..1> characteristics
Input impedance		10 kΩ
Coupling		DC
Protection
Power on		±30 V
Power off		±15 V
Range		±11 V
Slew rate		20 V/µs
Calibration (AI and AO)
Recommended warm-up time		15 minutes
Calibration interval		2 years

AI Absolute Accuracy Table
Nominal Range		Residual Gain Error (ppm of Reading)	Gain Tempco (ppm/°C)	Reference Tempco	Residual Offset Error (ppm of Range)	Offset Tempco (ppm of Range/°C)	INL Error (ppm of Range)	Random Noise, σ (µVrms)	Absolute Accuracy at Full Scale1 (µV)	Sensitivity2 (µV)
Positive Full Scale	Negative Full Scale
10	-10	60	13	1	20	21	60	280	1,920	112.0
5	-5	70	13	1	20	21	60	140	1,010	56.0
2	-2	70	13	1	20	24	60	57	410	22.8
1	-1	80	13	1	20	27	60	32	220	12.8
0.5	- 0.5	90	13	1	40	34	60	21	130	8.4
0.2	- 0.2	130	13	1	80	55	60	16	74	6.4
0.1	- 0.1	150	13	1	150	90	60	15	52	6.0
Accuracies listed are valid for up to two years from the device external calibration. AbsoluteAccuracy = Reading · (GainError) + Range · (OffsetError) + NoiseUncertainty GainError = ResidualAIGainError + GainTempco · (TempChangeFromLastInternalCal) + ReferenceTempco · (TempChangeFromLastExternalCal) OffsetError = ResidualAIOffsetError + OffsetTempco · (TempChangeFromLastInternalCal) + INL_Error 1 Absolute accuracy at full scale on the analog input channels is determined using the following assumptions: TempChangeFromLastExternalCal = 10 °C TempChangeFromLastInternalCal = 1 °C number_of_readings = 100 CoverageFactor = 3 σ For example, on the 10 V range, the absolute accuracy at full scale is as follows: GainError = 60 ppm + 13 ppm · 1 + 1 ppm · 10       GainError = 83 ppm OffsetError = 20 ppm + 21 ppm · 1 + 60 ppm         OffsetError = 101 ppm AbsoluteAccuracy = 10 V · (GainError) + 10 V · (OffsetError) + NoiseUncertainty      AbsoluteAccuracy = 1920 µV 2 Sensitivity is the smallest voltage change that can be detected. It is a function of noise.

 

AO Absolute Accuracy Table
Nominal Range		Residual Gain Error (ppm of Reading)	Gain Tempco (ppm/°C)	Reference Tempco	Residual Offset Error (ppm of Range)	Offset Tempco (ppm of Range/°C)	INL Error (ppm of Range)	Absolute Accuracy at Full Scale1 (µV)
Positive Full Scale	Negative Full Scale
10	-10	75	17	1	40	2	64	2,080
5	-5	85	8	1	40	2	64	1,045
1 Absolute Accuracy at full scale numbers is valid immediately following internal calibration and assumes the device is operating within 10 °C of the last external calibration. Accuracies listed are valid for up to two years from the device external calibration. AbsoluteAccuracy = OutputValue · (GainError) + Range · (OffsetError) GainError = ResidualGainError + GainTempco · (TempChangeFromLastInternalCal) + ReferenceTempco · (TempChangeFromLastExternalCal) OffsetError = ResidualOffsetError + AOOffsetTempco · (TempChangeFromLastInternalCal) + INL_Error

 

Digital I/O/PFI
Static Characteristics
Number of channels
NI 6250/6251/6255		24 total, 8 (P0.<0..7>), 16 (PFI <0..7>/P1, PFI <8..15>/P2)
NI 6254/6259		48 total, 32 (P0.<0..31>), 16 (PFI <0..7>/P1, PFI <8..15>/P2)
Ground reference		D GND
Direction control		Each terminal individually programmable as input or output
Pull-down resistor		50 kΩ typ, 20 kΩ min
Input voltage protection3		±20 V on up to two pins
3  Stresses beyond those listed under Input voltage protection may cause permanent damage to the device.
Waveform Characteristics (Port 0 Only)
Terminals used
NI 6250/6251/6255		Port 0 (P0.<0..7>)
NI 6254/6259		Port 0 (P0.<0..31>)
Port/sample size
NI 6250/6251/6255		Up to 8 bits
NI 6254/6259		Up to 32 bits
Waveform generation (DO) FIFO		2,047 samples
Waveform acquisition (DI) FIFO		2,047 samples
DI Sample Clock frequency
PCI/PCIe/PXI/PXIe devices		0 to 10 MHz4
USB devices		0 to 1 MHz system dependent4
DO Sample Clock frequency
PCI/PCIe/PXI/PXIe devices
Regenerate from FIFO		0 to 10 MHz
Streaming from memory		0 to 1 MHz system dependent4
USB devices
Regenerate from FIFO		0 to 10 MHz
Streaming from memory		0 to 1 MHz system dependent4
Data transfers
PCI/PCIe/PXI/PXIe devices		DMA (scatter-gather), interrupts, programmed I/O
USB devices		USB Signal Stream, programmed I/O
DO or DI Sample Clock source5		Any PFI, RTSI, AI Sample or Convert Clock, AO Sample Clock, Ctr n Internal Output, and many other signals
4  Performance can be dependent on bus latency and volume of bus activity. 5  The digital subsystem does not have its own dedicated internal timing engine. Therefore, a sample clock must be provided from another subsystem on the device or an external source.
PFI/Port 1/Port 2 Functionality
Functionality		Static digital input, static digital output, timing input, timing output
Timing output sources		Many AI, AO, counter, DI, DO timing signals
Debounce filter settings		125 ns, 6.425 µs, 2.56 ms, disable; high and low transitions; selectable per input

 

Recommended Operation Conditions6
Level	Min	Max
Input high voltage (VIH)	2.2 V	5.25 V
Input low voltage (VIL)	0 V	0.8 V
Output high current (IOH)    P0.<0..31>    PFI <0..15>/P1/P2	— —	-24 mA -16 mA
Output low current (IOL)    P0.<0..31>    PFI <0..15>/P1/P2	— —	24 mA 16 mA

 

Electrical Characteristics
Level	Min	Max
Positive-going threshold (VT+) Negative-going threshold (VT-)	— 0.8 V	2.2 V —
Delta VT hysteresis (VT+ - VT-)	0.2 V	—
IIL input low current (Vin = 0 V) IIH input high current (Vin = 5 V)	— —	-10 µA 250 µA

 

Digital I/O Characteristics6
6  On earlier versions of the USB-6251 Screw Terminal (part numbers 194929A/B/C-0x) and the USB-6259 Screw Terminal (part numbers 194021B/C-0x), the digital I/O characteristics of P0.<16..31> match the characteristics of PFI <0..15>. Refer to the November 2006 version of the NI 625x Specifications (part number 371291G-01) for more details.

General-Purpose Counter/Timers
Number of counter/timers		2
Resolution		32 bits
Counter measurements		Edge counting, pulse, semi-period, period, two-edge separation
Position measurements		X1, X2, X4 quadrature encoding with Channel Z reloading; two-pulse encoding
Output applications		Pulse, pulse train with dynamic updates, frequency division, equivalent time sampling
Internal base clocks		80 MHz, 20 MHz, 0.1 MHz
External base clock frequency		0 MHz to 20 MHz
Base clock accuracy		50 ppm
Inputs		Gate, Source, HW_Arm, Aux, A, B, Z, Up_Down
Routing options for inputs		Any PFI, RTSI, PXI_TRIG, PXI_STAR, analog trigger, many internal signals
FIFO		2 samples
Data transfers
PCI/PCIe/PXI/PXIe devices		Dedicated scatter-gather DMA controller for each counter/timer; interrupts, programmed I/O
USB devices		USB Signal Stream, programmed I/O
Frequency Generator
Number of channels		1
Base clocks		10 MHz, 100 kHz
Divisors		1 to 16
Base clock accuracy		50 ppm
Output can be available on any PFI or RTSI terminal.
Phase-Locked Loop (PLL)
Number of PLLs		1
Reference signal		PXI_STAR, PXI_CLK10, RTSI <0..7>
Output of PLL		80 MHz Timebase; other signals derived from 80 MHz Timebase including 20 MHz and 100 kHz Timebases
External Digital Triggers
Source		Any PFI, RTSI, PXI_TRIG, PXI_STAR
Polarity		Software-selectable for most signals
Analog input function		Start Trigger, Reference Trigger, Pause Trigger, Sample Clock, Convert Clock, Sample Clock Timebase
Analog output function		Start Trigger, Pause Trigger, Sample Clock, Sample Clock Timebase
Counter/timer functions		Gate, Source, HW_Arm, Aux, A, B, Z, Up_Down
Digital waveform generation (DO) function		Sample Clock
Digital waveform acquisition (DI) function		Sample Clock
Device-To-Device Trigger Bus
PCI/PCIe devices		RTSI <0..7>7
PXI/PXIe devices		PXI_TRIG <0..7>, PXI_STAR
USB devices		None
Output selections		10 MHz Clock; frequency generator output; many internal signals
Debounce filter settings		125 ns, 6.425 µs, 2.56 ms, disable; high and low transitions; selectable per input
7  In other sections of this document, RTSI refers to RTSI <0..7> for PCI/PCIe devices or PXI_TRIG <0..7> for PXI/PXIe devices.
Bus Interface
PCI/PXI devices		3.3 V or 5 V signal environment
PCIe devices
Form factor		x1 PCI Express, specification v1.0a compliant
Slot compatibility		x1, x4, x8, and x16 PCI Express slots8
PXIe devices
Form factor		x1 PXI Express peripheral module, specification rev 1.0 compliant
Slot compatibility		x1 and x4 PXI Express or PXI Express hybrid slots
USB devices		USB 2.0 Hi-Speed or full-speed9,10
DMA channels (PCI/PCIe/PXI/PXIe devices)		6, analog input, analog output, digital input, digital output, counter/timer 0, counter/timer 1
USB Signal Stream (USB devices)		4, can be used for analog input, analog output, digital input, digital output, counter/timer 0, counter/timer 1
All PXI-625x devices support one of the following features: May be installed in PXI Express hybrid slots Or, may be used to control SCXI in PXI/SCXI combo chassis
Table 1. PXI/SCXI Combo and PXI Express Chassis Compatibility M Series Device M Series Part Number SCXI Control in PXI/SCXI Combo Chassis PXI Express Hybrid Slot Compatible PXI-6250 191325D-04/191325E-04L No Yes PXI-6251 191325D-03/191325E-03L No Yes 191325D-13/191325E-13L Yes No PXI-6254 191325D-02/191325E-03L No Yes PXI-6255 193618A-01 No Yes PXI-6259 191325D-01/191325E-01L No Yes 191325D-11/191325E-11L Yes No Earlier versions of PXI-6251/ 6254/6259 191325C-0x 191325B-0x Yes No All NI PXIe-625x devices may be installed in PXI Express slots or PXI Express hybrid slots.
8  Some motherboards reserve the x16 slot for graphics use. For PCI Express guidelines, refer to ni.com/pciexpress. 9  If you are using a USB M Series device in full-speed mode, device performance will be lower and you will not be able to achieve maximum sampling/update rates. 10  Operating on a full-speed bus may result in lower high-speed full-speed performance.
Power Requirements
Current draw from bus during no-load condition11
PCI/PXI devices
+5 V		0.03 A
+3.3 V		0.725 A
+12 V		0.35 A
PCIe devices
+3.3 V		0.925 A
+12 V		0.35 A
PXIe devices
+3.3 V		0.45 A
+12 V		0.5 A
Current draw from bus during AI and AO overvoltage condition11
PCI/PXI devices
+5 V		0.03 A
+3.3 V		1.2 A
+12 V		0.38 A
PCIe devices
+3.3 V		1.4 A
+12 V		0.38 A
PXIe devices
+3.3 V		0.48 A
+12 V		0.71 A

Caution USB-625x devices must be powered with NI offered AC adapter or a National Electric Code (NEC) Class 2 DC source that meets the power requirements
for the device and has appropriate safety certification marks for country of use.

USB power supply requirements		11 to 30 VDC, 20 W, locking or non-locking power jack with 0.080" diameter center pin, 5/16-32 thread for locking collars
11  Does not include P0/PFI/P1/P2 and +5 V terminals.
Power Limits
Caution  Exceeding the power limits may cause unpredictable behavior by the device and/or PC/chassis.
PCI devices
+5 V terminal (connector 0)		1 A max12
+5 V terminal (connector 1)		1 A max12
PCIe devices
Without disk drive power connector installed
+5 V terminals combined		0.35 A max12
P0/PFI/P1/P2 and +5 V terminals combined		0.39 A max
With disk drive power connector installed
+5 V terminal (connector 0)		1 A max12
+5 V terminal (connector 1)		1 A max12
P0/PFI/P1/P2 combined		0.39 A max
PXI/PXIe devices
+5 V terminal (connector 0)		1 A max12
+5 V terminal (connector 1)		1 A max12
P0/PFI/P1/P2 and +5 V terminals combined		2 A max
USB devices
+5 V terminal		1 A max12
P0/PFI/P1/P2 and +5 V terminals combined		2 A max
Power supply fuse		2 A, 250 V
12  Has a self-resetting fuse that opens when current exceeds this specification.
Physical Requirements
Printed circuit board dimensions
NI PCI-6250/6251/6254/6255/6259		9.7 × 15.5 cm (3.8 × 6.1 in.)
NI PCIe-6251/6259		9.9 × 16.8 cm (3.9 × 6.6 in.) (half-length)
NI PXI/PXIe-6250/6251/6254/6255/6259		Standard 3U PXI
Enclosure dimensions (includes connectors)
NI USB-6251/6255/6259 Screw Terminal		26.67 × 17.09 × 4.45 cm (10.5 × 6.73 × 1.75 in.)
NI USB-6251/6259 BNC		28.6 × 17 × 6.9 cm (11.25 × 6.7 × 2.7 in.)
NI USB-6251/6255/6259 Mass Termination