NI6251
DEVICE SPECIFICATIONS
NI 6251
M Series Data Acquisition:16 AI, 1.25 MS/s, 24 DIO, 2 AO
The following specifications are typical at 25 °C, unless otherwise noted. For more information about the NI 6251, refer to the M Series User Guide available at https://www.wendangku.net/doc/ff2954684.html,/manuals. Analog Input
Number of channels8 differential or 16 single ended
ADC resolution16 bits
DNL No missing codes guaranteed
INL Refer to the AI Absolute Accuracy section Sample rate
Single channel maximum 1.25 MS/s
Multichannel maximum (aggregate) 1.00 MS/s
Minimum No minimum
Timing resolution50 ns
Timing accuracy50 ppm of sample rate
Input coupling DC
Input range±0.1 V, ±0.2 V, ±0.5 V, ±1 V, ±2 V, ±5 V,
±10 V
±11 V of AI GND
Maximum working voltage for analog inputs
(signal + common mode)
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 GND820 Ω
AI- to AI GND820 Ω
Input bias current±100 pA
Crosstalk (at 100 kHz)
Adjacent channels-75 dB
Non-adjacent channels-95 dB
Small signal bandwidth (-3 dB) 1.7 MHz
Input FIFO size4,095 samples
Scan list memory4,095 entries
Data transfers
PCI/PCI Express/PXI/PXI Express DMA (scatter-gather), interrupts,
programmed I/O
USB USB Signal Stream, programmed I/O Overvoltage protection for all analog input and sense channels
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 maximum/AI pin Settling Time for Multichannel Measurements
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Typical Performance Graphs
Figure 1. Settling Error versus Time for Different Source Impedances
Time (μs)
E r r o r (p p m o f S t e p S i z e )
Figure 2. AI Small Signal Bandwidth
–8–7–6–5–4–3–2–1011 k
10 k
100 k
1000 k
10000 k
Frequency (Hz)
N o r m a l i z e d S i g n a l A m p l i t u d e (d B )
NI 6251 Device Specifications | ? National Instruments | 3
Figure 3. AI CMRR
Frequency (Hz)
C
M
R
R
(
d
B
)
AI Absolute Accuracy
Note Accuracies listed are valid for up to two years from the device external
calibration.
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Note Sensitivity is the smallest voltage change that can be detected. It is a function
of noise.
Gain tempco13 ppm/°C
Reference tempco 1 ppm/°C
INL error60 ppm of range
AI Absolute Accuracy Equation
AbsoluteAccuracy = Reading · (GainError) + Range · (OffsetError) + NoiseUncertainity GainError = ResidualAIGainError + GainTempco · (TempChangeFromLastInternalCal) + ReferenceTempco · (TempChangeFromLastExternalCal)
OffsetError = ResidualAIOffsetError + OffsetTempco ·
(TempChangeFromLastInternalCal) + INLError
NoiseUncertainty
100 points.
AI Absolute Accuracy Example
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 = 83 ppm
OffsetError = 20 ppm + 21 ppm · 1 + 60 ppm = 101 ppm
AbsoluteAccuracy = 10 V · (GainError) + 10 V · (OffsetError) + NoiseUncertainity = 1,920 μV
Analog Triggers
Number of triggers1
Source AI <0..15>, APFI 0
Functions Start Trigger, Reference Trigger,
Pause Trigger, Sample Clock, Convert Clock,
Sample Clock Timebase
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Source level
AI <0..15>±Full scale
APFI 0±10 V
Resolution10 bits, 1 in 1,024
Modes Analog edge triggering, analog edge triggering
with hysteresis, and analog window triggering Bandwidth (-3 dB)
AI <0..15> 3.4 MHz
APFI 0 3.9 MHz
Accuracy±1%
APFI 0 characteristics
Input impedance10 kΩ
Coupling DC
Protection, power on±30 V
Protection, power off±15 V
Analog Output
Number of channels2
DAC resolution16 bits
DNL±1 LSB
Monotonicity16 bit guaranteed
Accuracy Refer to the AO Absolute Accuracy section Maximum update rate
1 channel 2.86 MS/s
2 channels 2.00 MS/s per channel
Timing accuracy50 ppm of sample rate
Timing resolution50 ns
Output range±5 V, ±10 V, ±external reference on APFI 0 Output coupling DC
Output impedance0.2 Ω
Output current drive±5 mA
Overdrive protection±25 V
Overdrive current20 mA
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Power-on state ±5 mV 1
Power-on glitch 1.5 V peak for 1.5 s
Output FIFO size 8,191 samples shared among channels used Data transfers
PCI/PCI Express/PXI/PXI Express DMA (scatter-gather), interrupts,programmed I/O
USB
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
AO Absolute Accuracy
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.
Note Accuracies listed are valid for up to two years from the device external
calibration.
Reference tempco 1 ppm/°C INL error
64 ppm of range
1
When the USB Screw Terminal device is powered on, the analog output signal is not defined until after USB configuration is complete.
NI 6251 Device Specifications | ? National Instruments | 7
AO Absolute Accuracy Equation
AbsoluteAccuracy = OutputValue · (GainError) + Range · (OffsetError )
GainError = ResidualGainError + GainTempco · (TempChangeFromLastInternalCal ) +ReferenceTempco · (TempChangeFromLastExternalCal )OffsetError = ResidualOffsetError + AOOffsetTempco ·(TempChangeFromLastInternalCal) + INLError
External Reference
APFI 0 characteristics
Input impedance 10 k?Coupling
DC Protection, device on ±30 V Protection, device off ±15 V Range ±11 V Slew rate
20 V/μs
Figure 4. AO External Reference Bandwidth
Frequency (Hz)
N o r m a l i z e d A O A m p l i t u d e A t t e n u a t i o n (d B )
Digital I/O/PFI
Static Characteristics
Number of channels 24 total, 8 (P0.<0..7>),
16 (PFI <0..7>/P1, PFI <8..15>/P2)Ground reference
D GND
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Direction control Each terminal individually programmable as
input or output
Pull-down resistor50 kΩ typical, 20 kΩ minimum
Input voltage protection±20 V on up to two pins2 Waveform Characteristics (Port 0 Only)
Terminals used Port 0 (P0.<0..7>)
Port/sample size Up to 8 bits
Waveform generation (DO) FIFO2,047 samples
Waveform acquisition (DI) FIFO2,047 samples
DI Sample Clock frequency
PCI/PCI Express/PXI/PXI Express0 MHz to 10 MHz, system and bus activity
dependent
USB0 MHz to 1 MHz, system and bus activity
dependent
DO Sample Clock frequency
PCI/PCI Express/PXI/PXI Express
Regenerate from FIFO0 MHz to 10 MHz
Streaming from memory0 to 10 MHz, system and bus activity
dependent
USB
Regenerate from FIFO0 MHz to 10 MHz
Streaming from memory0 MHz to 1 MHz, system and bus activity
dependent
Data transfers
PCI/PCI Express/PXI/PXI Express DMA (scatter-gather), interrupts,
programmed I/O
USB USB Signal Stream, programmed I/O
DI or DO Sample Clock source3Any PFI, RTSI, AI Sample or Convert Clock,
AO Sample Clock, Ctr n Internal Output, and
many other signals
2Stresses beyond those listed under Input voltage protection may cause permanent damage to the device.
3The 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.
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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 settings125 ns, 6.425 μs, 2.56 ms, disable; high and
low transitions; selectable per input Recommended Operating Conditions
Electrical Characteristics
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Digital I/O Characteristics
Figure 5. P0.<0..7>: I oh versus V oh
V oh (V)
I o h (m A )
Figure 6. PFI <0..15>/P1/P2: I oh versus V oh
–50
–45–40
–35–30–25–20–15–10–50V oh (V)
I o h (m A )
NI 6251 Device Specifications | ? National Instruments | 11
Figure 7. P0.<0..7>: I ol versus V ol
V ol (V)
I o l (m A )
Figure 8. PFI <0..15>/P1/P2: I ol versus V
ol
V ol (V)
I o l (m A )
General-Purpose Counters/Timers
Number of counter/timers 2Resolution
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
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Internal base clocks80 MHz, 20 MHz, 0.1 MHz
External base clock frequency0 MHz to 20 MHz
Base clock accuracy50 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/PCI Express/PXI/PXI Express Dedicated scatter-gather DMA controller for
each counter/timer; interrupts,
programmed I/O
USB USB Signal Stream, programmed I/O Frequency Generator
Number of channels1
Base clocks10 MHz, 100 kHz
Divisors 1 to 16
Base clock accuracy50 ppm
Output can be available on any output PFI or RTSI terminal.
Phase-Locked Loop (PLL)
Note PCI/PCI Express/PXI/PXI Express devices only.
Number of PLLs1
Reference signal PXI_STAR, PXI_CLK10, RTSI <0..7> Output of PLL80 MHz Timebase; other signals derived from
80 MHz Timebase including 20 MHz and
100 kHz Timebases
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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 function 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 T rigger Bus
PCI/PCI Express RTSI <0..7>4
PXI/PXI Express PXI_TRIG <0..7>, PXI_STAR
USB source None
Output selections10 MHz Clock, frequency generator output,
many internal signals
Debounce filter settings125 ns, 6.425 μs, 2.56 ms, disable; high and
low transitions; selectable per input
Bus Interface
PCI/PXI 3.3 V or 5 V signal environment
PCI Express
Form factor x1 PCI Express, specification v1.0a compliant Slot compatibility x1, x4, x8, and x16 PCI Express slots5
4In other sections of this document, RTSI refers to RTSI <0..7> for the PCI/PCI Express devices or PXI_TRIG <0..7> for PXI/PXI Express devices.
5Some motherboards reserve the x16 for graphics use. For PCI Express guidelines, refer to https://www.wendangku.net/doc/ff2954684.html,/ pciexpress.
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PXI Express
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 USB 2.0 Hi-Speed or full-speed6, 7
DMA channels (PCI/PCI Express/ PXI/PXI Express)6, can be used for analog input, analog output, digital input, digital output, counter/timer 0, counter/timer 1
USB Signal Stream4, can be used for analog input, analog output,
digital input, digital output, counter/timer 0,
counter/timer 1
The PXI device supports 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
The PXI Express device can be installed in PXI Express slots or PXI Express hybrid slots. Power Requirements
Current draw from bus during no-load condition8
PCI/PXI
+5 V0.03 A
+3.3 V0.725 A
+12 V0.35 A
6If you are using an USB M Series device in full-speed mode, device performance will be lower and you will not be able to achieve maximum sample/update rates.
7Operating on a full-speed bus may result in lower performance.
8Does not include P0/PFI/P1/P2 and +5 V terminals.
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PCI Express
+3.3 V0.925 A
+12 V0.35 A
PXI Express
+3.3 V0.45 A
+12 V0.5 A
Current draw from bus during AI and AO overvoltage condition8
PCI/PXI
+5 V0.03 A
+3.3 V 1.2 A
+12 V0.38 A
PCI Express
+3.3 V 1.4 A
+12 V0.38 A
PXI Express
+3.3 V0.48 A
+12 V0.71 A
Caution USB devices must be powered with an 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 requirements11 to 30 VDC, 20 W, locking or non-locking
power jack with 0.080 in. diameter center pin,
5/16-32 thread for locking collars
Current Limits
Caution Exceeding the current limits may cause unpredictable behavior by the
device and/or PC/chassis.
PCI, +5 V terminal 1 A maximum9
9Older revisions have a self-resetting fuse that opens when current exceeds this specification. Newer revisions have a traditional fuse that opens when current exceeds this specification. This fuse is not customer-replaceable; if the fuse permanently opens, return the device to NI for repair.
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PCI Express
Without disk drive power connector installed
+5 V terminals combined0.35 A maximum9
P0/PFI/P1/P2 and +5 V terminals
combined
0.39 A maximum
With disk drive power connector installed
+5 V terminal 1 A maximum9
P0/PFI/P1/P2 combined0.39 A maximum
PXI/PXI Express
+5 V terminal 1 A maximum9
P0/PFI/P1/P2 and +5 V terminals
combined
2 A maximum
USB
+5 V terminal 1 A maximum9
P0/PFI/P1/P2 and +5 V terminals
combined
2 A maximum
Power supply fuse 2 A, 250 V
Physical Characteristics
Dimensions
PCI printed circuit board10.6 cm × 15.5 cm (4.2 in. × 6.1 in.) PCI Express printed circuit board9.9 cm × 16.8 cm (3.9 in. × 6.6 in.)
(half-length)
PXI/PXI Express printed circuit board Standard 3U PXI
USB Screw Terminal enclosure (includes connectors)26.67 cm × 17.09 cm × 4.45 cm (10.5 in. × 6.73 in. × 1.75 in.)
USB BNC enclosure (includes connectors)28.6 cm × 17 cm × 6.9 cm (11.25 in. × 6.7 in. × 2.7 in.)
USB Mass Termination enclosure (includes connectors)18.8 cm × 17.09 cm × 4.45 cm (7.4 in. × 6.73 in. × 1.75 in.)
USB OEM Refer to the NI USB-622x/625x/628x OEM
User Guide
NI 6251 Device Specifications| ? National Instruments| 17
Weight
PCI149 g (5.2 oz)
PCI Express161 g (5.7 oz)
PXI222 g (7.8 oz)
PXI Express208 g (7.3 oz)
USB Screw Terminal 1.2 kg (2 lb 10 oz)
USB Mass Termination816 g (1 lb 12.8 oz)
USB OEM140 g (4.9 oz)
I/O connector
PCI/PCI Express/PXI/PXI Express 1 68-pin VHDCI
USB Screw Terminal64 screw terminals
USB BNC21 BNCs and 30 screw terminals
Mass Termination 1 68-pin SCSI
PCI Express disk drive power Standard ATX peripheral connector
(not serial ATA)
16 to 28 AWG
USB Screw Terminal/BNC screw terminal
wiring
Calibration
Recommended warm-up time
PCI/PXI/PCI Express/PXI Express15 minutes
USB30 minutes
Calibration interval 2 years
Maximum Working Voltage
Maximum working voltage refers to the signal voltage plus the common-mode voltage. Channel-to-earth11 V, Measurement Category I Measurement Category I is for measurements performed on circuits not directly connected to the electrical distribution system referred to as MAINS voltage. MAINS is a hazardous live electrical supply system that powers equipment. This category is for measurements of voltages from specially protected secondary circuits. Such voltage measurements include signal levels, special equipment, limited-energy parts of equipment, circuits powered by regulated low-voltage sources, and electronics.
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Caution Do not use for measurements within Categories II, III, or IV.
Note Measurement Categories CAT I and CAT O (Other) are equivalent. These test
and measurement circuits are not intended for direct connection to the MAINS
building installations of Measurement Categories CAT II, CAT III, or CAT IV. Environmental
Operating temperature
PCI/PXI/PXI Express0 oC to 55 oC
PCI Express0 oC to 50 oC
USB0 oC to 45 oC
Storage temperature-20 oC to 70 oC
Humidity10% RH to 90% RH, noncondensing Maximum altitude2,000 m
Pollution Degree (indoor use only)2
Indoor use only.
Shock and Vibration (PXI and PXI Express Only)
Operational shock30 g peak, half-sine, 11 ms pulse (Tested in
accordance with IEC 60068-2-27. Test profile
developed in accordance with
MIL-PRF-28800F.)
Random vibration
Operating 5 Hz to 500 Hz, 0.3 g rms
Nonoperating 5 Hz to 500 Hz, 2.4 g rms (Tested in accordance
with IEC 60068-2-64. Nonoperating test
profile exceeds the requirements of
MIL-PRF-28800F, Class 3.)
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Safety
This product is designed to meet the requirements of the following electrical equipment safety standards for measurement, control, and laboratory use:
?IEC 61010-1, EN 61010-1
?UL 61010-1, CSA 61010-1
Note For UL and other safety certifications, refer to the product label or the Online
Product Certification section.
Electromagnetic Compatibility
This product meets the requirements of the following EMC standards for electrical equipment for measurement, control, and laboratory use:
?EN 61326-1 (IEC 61326-1): Class A emissions; Basic immunity
?EN 55011 (CISPR 11): Group 1, Class A emissions
?AS/NZS CISPR 11: Group 1, Class A emissions
?FCC 47 CFR Part 15B: Class A emissions
?ICES-001: Class A emissions
Note In the United States (per FCC 47 CFR), Class A equipment is intended for
use in commercial, light-industrial, and heavy-industrial locations. In Europe,
Canada, Australia, and New Zealand (per CISPR 11) Class A equipment is intended
for use only in heavy-industrial locations.
Note Group 1 equipment (per CISPR 11) is any industrial, scientific, or medical
equipment that does not intentionally generate radio frequency energy for the
treatment of material or inspection/analysis purposes.
Note For EMC declarations and certifications, refer to the Online Product
Certification section.
CE Compliance
This product meets the essential requirements of applicable European Directives, as follows:?2014/35/EU; Low-V oltage Directive (safety)
?2014/30/EU; Electromagnetic Compatibility Directive (EMC)
?2011/65/EU; Restriction of Hazardous Substances (RoHS)
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