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NI-DAQmx C Reference Help
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NI-DAQmx Concepts
NI-DAQmx C Functions
Task Configuration/Control
DAQmxAddGlobalChansToTask
DAQmxClearTask
DAQmxConfigureLogging
DAQmxCreateTask
DAQmxIsTaskDone
DAQmxLoadTask
DAQmxStartTask
DAQmxStartNewFile
DAQmxStopTask
DAQmxWaitUntilTaskDone
Events
DAQmxRegisterDoneEvent
DAQmxRegisterEveryNSamplesEvent
DAQmxRegisterSignalEvent
Advanced
DAQmxGetNthTaskChannel
DAQmxGetNthTaskDevice
DAQmxTaskControl
Channel Configuration/Creation
Create Analog Input Channels
DAQmxCreateAIAccelChan
DAQmxCreateAIBridgeChan
DAQmxCreateAICurrentChan
DAQmxCreateAICurrentRMSChan
DAQmxCreateAIForceBridgePolynomialChan
DAQmxCreateAIForceBridgeTableChan
DAQmxCreateAIForceBridgeTwoPointLinChan
DAQmxCreateAIForceIEPEChan
DAQmxCreateAIFreqVoltageChan
DAQmxCreateAIMicrophoneChan
DAQmxCreateAIPressureBridgePolynomialChan
DAQmxCreateAIPressureBridgeTableChan
DAQmxCreateAIPressureBridgeTwoPointLinChan
DAQmxCreateAIResistanceChan
DAQmxCreateAIRosetteStrainGageChan
DAQmxCreateAIRTDChan
DAQmxCreateAIStrainGageChan
DAQmxCreateAITempBuiltInSensorChan
DAQmxCreateAIThrmcplChan
DAQmxCreateAIThrmstrChanIex
DAQmxCreateAIThrmstrChanVex
DAQmxCreateAITorqueBridgePolynomialChan
DAQmxCreateAITorqueBridgeTableChan
DAQmxCreateAITorqueBridgeTwoPointLinChan
DAQmxCreateAIVelocityIEPEChan
DAQmxCreateAIVoltageChan
DAQmxCreateAIVoltageRMSChan
DAQmxCreateAIVoltageChanWithExcit
Position
DAQmxCreateAIPosEddyCurrProxProbeChan
DAQmxCreateAIPosLVDTChan
DAQmxCreateAIPosRVDTChan
Obsolete
DAQmxCreateAIDeviceTempChan
Create TEDS Analog Input Channels
DAQmxCreateTEDSAIAccelChan
DAQmxCreateTEDSAICurrentChan
DAQmxCreateTEDSAIBridgeChan
DAQmxCreateTEDSAIForceBridgeChan
DAQmxCreateTEDSAIForceIEPEChan
DAQmxCreateTEDSAIMicrophoneChan
DAQmxCreateTEDSAIPressureBridgeChan
DAQmxCreateTEDSAIResistanceChan
DAQmxCreateTEDSAIRTDChan
DAQmxCreateTEDSAIStrainGageChan
DAQmxCreateTEDSAIThrmcplChan
DAQmxCreateTEDSAIThrmstrChanIex
DAQmxCreateTEDSAIThrmstrChanVex
DAQmxCreateTEDSAITorqueBridgeChan
DAQmxCreateTEDSAIVoltageChan
DAQmxCreateTEDSAIVoltageChanWithExcit
Position
DAQmxCreateTEDSAIPosLVDTChan
DAQmxCreateTEDSAIPosRVDTChan
Create Analog Output Channel
DAQmxCreateAOCurrentChan
DAQmxCreateAOFuncGenChan
DAQmxCreateAOVoltageChan
Create Digital Input Channels
DAQmxCreateDIChan
Create Digital Output Channels
DAQmxCreateDOChan
Create Counter Input Channels
DAQmxCreateCICountEdgesChan
DAQmxCreateCIFreqChan
DAQmxCreateCIPeriodChan
DAQmxCreateCIPulseChanFreq
DAQmxCreateCIPulseChanTicks
DAQmxCreateCIPulseChanTime
DAQmxCreateCIPulseWidthChan
DAQmxCreateCISemiPeriodChan
DAQmxCreateCITwoEdgeSepChan
Position
DAQmxCreateCILinEncoderChan
DAQmxCreateCIAngEncoderChan
Timestamp
DAQmxCreateCIGPSTimestampChan
Create Counter Output Channels
DAQmxCreateCOPulseChanFreq
DAQmxCreateCOPulseChanTicks
DAQmxCreateCOPulseChanTime
Timing
DAQmxCfgBurstHandshakingTimingExportClock
DAQmxCfgBurstHandshakingTimingImportClock
DAQmxCfgChangeDetectionTiming
DAQmxCfgHandshakingTiming
DAQmxCfgImplicitTiming
DAQmxCfgPipelinedSampClkTiming
DAQmxCfgSampClkTiming
Triggering
Start Trigger
DAQmxCfgAnlgEdgeStartTrig
DAQmxCfgAnlgWindowStartTrig
DAQmxCfgDigEdgeStartTrig
DAQmxCfgDigPatternStartTrig
DAQmxDisableStartTrig
Reference Trigger
DAQmxCfgAnlgEdgeRefTrig
DAQmxCfgAnlgWindowRefTrig
DAQmxCfgDigEdgeRefTrig
DAQmxCfgDigPatternRefTrig
DAQmxDisableRefTrig
Advanced Trigger
DAQmxCfgDigEdgeAdvTrig
DAQmxDisableAdvTrig
DAQmxSendSoftwareTrigger
Read Functions
DAQmxReadAnalogF64
DAQmxReadAnalogScalarF64
DAQmxReadBinaryI16
DAQmxReadBinaryI32
DAQmxReadBinaryU16
DAQmxReadBinaryU32
DAQmxReadCounterF64
DAQmxReadCounterScalarF64
DAQmxReadCounterScalarU32
DAQmxReadCounterU32
DAQmxReadCtrFreq
DAQmxReadCtrFreqScalar
DAQmxReadCtrTicks
DAQmxReadCtrTicksScalar
DAQmxReadCtrTime
DAQmxReadCtrTimeScalar
DAQmxReadDigitalLines
DAQmxReadDigitalScalarU32
DAQmxReadDigitalU8
DAQmxReadDigitalU16
DAQmxReadDigitalU32
Advanced
DAQmxGetNthTaskReadChannel
DAQmxReadRaw
Write Functions
DAQmxWriteAnalogF64
DAQmxWriteAnalogScalarF64
DAQmxWriteBinaryI16
DAQmxWriteBinaryU16
DAQmxWriteCtrFreq
DAQmxWriteCtrFreqScalar
DAQmxWriteCtrTicks
DAQmxWriteCtrTicksScalar
DAQmxWriteCtrTime
DAQmxWriteCtrTimeScalar
DAQmxWriteDigitalLines
DAQmxWriteDigitalScalarU32
DAQmxWriteDigitalU8
DAQmxWriteDigitalU16
DAQmxWriteDigitalU32
Advanced
DAQmxWriteRaw
Export HW Signals
DAQmxExportSignal
Scale Configuration
DAQmxCalculateReversePolyCoeff
DAQmxCreateLinScale
DAQmxCreateMapScale
DAQmxCreatePolynomialScale
DAQmxCreateTableScale
Internal Buffer Configuration
DAQmxCfgInputBuffer
DAQmxCfgOutputBuffer
Advanced Functions
Real-Time
DAQmxWaitForNextSampleClock
Obsolete
DAQmxIsReadOrWriteLate
Switch Functions
DAQmxSwitchCloseRelays
DAQmxSwitchConnect
DAQmxSwitchConnectMulti
DAQmxSwitchCreateScanList
DAQmxSwitchDisconnect
DAQmxSwitchDisconnectAll
DAQmxSwitchDisconnectMulti
DAQmxSwitchFindPath
DAQmxSwitchGetMultiRelayCount
DAQmxSwitchGetMultiRelayPos
DAQmxSwitchGetSingleRelayCount
DAQmxSwitchGetSingleRelayPos
DAQmxSwitchOpenRelays
DAQmxSwitchSetTopologyAndReset
DAQmxSwitchWaitForSettling
Signal Routing
DAQmxConnectTerms
DAQmxDisconnectTerms
DAQmxTristateOutputTerm
Device Control
DAQmxResetDevice
DAQmxSelfTestDevice
Watchdog
DAQmxControlWatchdogTask
DAQmxCreateWatchdogTimerTask
Calibration
DAQmxAOSeriesCalAdjust
DAQmxESeriesCalAdjust
DAQmxGetAIChanCalCalDate
DAQmxGetAIChanCalExpDate
DAQmxGetExtCalLastDateAndTime
DAQmxGetSelfCalLastDateAndTime
DAQmxMSeriesCalAdjust
DAQmxPerformBridgeOffsetNullingCal
DAQmxPerformBridgeOffsetNullingCalEx
DAQmxPerformBridgeShuntCal
DAQmxPerformStrainShuntCal
DAQmxPerformThrmcplLeadOffsetNullingCal
DAQmxRestoreLastExtCalConst
DAQmxSCBaseboardCalAdjust
DAQmxSelfCal
DAQmxSetAIChanCalCalDate
DAQmxSetAIChanCalExpDate
DAQmxSSeriesCalAdjust
DAQmxXSeriesCalAdjust
External Calibration
DAQmxChangeExtCalPassword
DAQmxCloseExtCal
DAQmxInitExtCal
DSA Calibration
DAQmxAdjustDSAAICal
DAQmxAdjustDSAAICalEx
DAQmxAdjustDSAAICalWithGainAndCoupling
DAQmxAdjustDSAAOCal
DAQmxAdjustDSATimebaseCal
PXI-42xx Calibration
DAQmxAdjust4204Cal
DAQmxAdjust4220Cal
DAQmxAdjust4224Cal
SCXI Calibration
DAQmxAdjust1102Cal
DAQmxAdjust1104Cal
DAQmxAdjust1112Cal
DAQmxAdjust1122Cal
DAQmxAdjust1124Cal
DAQmxAdjust1125Cal
DAQmxAdjust1126Cal
DAQmxAdjust1141Cal
DAQmxAdjust1142Cal
DAQmxAdjust1143Cal
DAQmxAdjust1502Cal
DAQmxAdjust1503Cal
DAQmxAdjust1503CurrentCal
DAQmxAdjust1520Cal
DAQmxAdjust1521Cal
DAQmxAdjust153xCal
DAQmxAdjust1540Cal
DAQmxSetup1102Cal
DAQmxSetup1104Cal
DAQmxSetup1112Cal
DAQmxSetup1122Cal
DAQmxSetup1124Cal
DAQmxSetup1125Cal
DAQmxSetup1126Cal
DAQmxSetup1141Cal
DAQmxSetup1142Cal
DAQmxSetup1143Cal
DAQmxSetup1502Cal
DAQmxSetup1503Cal
DAQmxSetup1520Cal
DAQmxSetup1521Cal
DAQmxSetup153xCal
DAQmxSetup1540Cal
SC Express Calibration
DAQmxAdjust4300Cal
DAQmxAdjust433xCal
DAQmxAdjust4353Cal
DAQmxSetup433xCal
DAQmxAdjust4357Cal
DAQmxConnectSCExpressCalAccChans
DAQmxDisconnectSCExpressCalAccChans
DAQmxGetPossibleSCExpressCalAccConnections
DAQmxSetSCExpressCalAccBridgeOutput
C Series Calibration
Adjust C Series Calibration
DAQmxAdjust9201Cal
DAQmxAdjust9203GainCal
DAQmxAdjust9203OffsetCal
DAQmxAdjust9205Cal
DAQmxAdjust9206Cal
DAQmxAdjust9207GainCal
DAQmxAdjust9207OffsetCal
DAQmxAdjust9208GainCal
DAQmxAdjust9208OffsetCal
DAQmxAdjust9211Cal
DAQmxAdjust9213Cal
DAQmxAdjust9214Cal
DAQmxAdjust9215Cal
DAQmxAdjust9217Cal
DAQmxAdjust9219Cal
DAQmxAdjust9220Cal
DAQmxAdjust9221Cal
DAQmxAdjust9222Cal
DAQmxAdjust9223Cal
DAQmxAdjust9225Cal
DAQmxAdjust9227Cal
DAQmxAdjust9232Cal
DAQmxAdjust9234GainCal
DAQmxAdjust9234OffsetCal
DAQmxAdjust9263Cal
DAQmxAdjust9264Cal
DAQmxAdjust9265Cal
DAQmxAdjust9269Cal
Get C Series Calibration Adjustment Points
DAQmxGet9201CalAdjustPoints
DAQmxGet9203CalAdjustPoints
DAQmxGet9207CalAdjustPoints
DAQmxGet9208CalAdjustPoints
DAQmxGet9213CalAdjustPoints
DAQmxGet9214CalAdjustPoints
DAQmxGet9215CalAdjustPoints
DAQmxGet9217CalAdjustPoints
DAQmxGet9219CalAdjustPoints
DAQmxGet9220CalAdjustPoints
DAQmxGet9221CalAdjustPoints
DAQmxGet9222CalAdjustPoints
DAQmxGet9223CalAdjustPoints
DAQmxGet9225CalAdjustPoints
DAQmxGet9227CalAdjustPoints
DAQmxGet9232CalAdjustPoints
DAQmxGet9234CalAdjustPoints
DAQmxGet9263CalAdjustPoints
DAQmxGet9264CalAdjustPoints
DAQmxGet9265CalAdjustPoints
DAQmxGet9269CalAdjustPoints
Setup C Series Calibration
DAQmxSetup9219Cal
DAQmxSetup9263Cal
DAQmxSetup9264Cal
DAQmxSetup9265Cal
DAQmxSetup9269Cal
DAQmxCSeriesSetCalTemp
Storage
DAQmxDeleteSavedGlobalChan
DAQmxDeleteSavedScale
DAQmxDeleteSavedTask
DAQmxSaveGlobalChan
DAQmxSaveScale
DAQmxSaveTask
TEDS
DAQmxClearTEDS
DAQmxConfigureTEDS
DAQmxWriteToTEDSFromArray
DAQmxWriteToTEDSFromFile
Network DAQ Functions
DAQmxAddNetworkDevice
DAQmxDeleteNetworkDevice
DAQmxReserveNetworkDevice
DAQmxUnreserveNetworkDevice
cDAQ Sync Functions
DAQmxAddCDAQSyncConnection
DAQmxAreConfiguredCDAQSyncPortsDisconnected
DAQmxAutoConfigureCDAQSyncConnections
DAQmxGetAutoConfiguredCDAQSyncConnections
DAQmxGetDisconnectedCDAQSyncPorts
DAQmxRemoveCDAQSyncConnection
System Configuration
DAQmxGetAnalogPowerUpStates
DAQmxGetDigitalLogicFamilyPowerUpState
DAQmxGetDigitalPowerUpStates
DAQmxGetDigitalPullUpPullDownStates
DAQmxSetAnalogPowerUpStates
DAQmxSetDigitalLogicFamilyPowerUpState
DAQmxSetDigitalPowerUpStates
DAQmxSetDigitalPullUpPullDownStates
Error Handling
DAQmxGetErrorString
DAQmxGetExtendedErrorInfo
NI-DAQmx C Properties
List of Buffer Properties
List of Calibration Info Properties
List of Channel Properties
List of Device Properties
List of Export Signal Properties
List of Persisted Channel Properties
List of Persisted Scale Properties
List of Persisted Task Properties
List of Physical Channel Properties
List of Read Properties
List of Real-Time Properties
List of Scale Properties
List of Switch Channel Properties
List of Switch Device Properties
List of Switch Scan Properties
List of System Properties
List of Task Properties
List of Timing Properties
List of Trigger Properties
List of Watchdog Properties
List of Write Properties
Glossary
Important Information
Warranty
Copyright
Trademarks
Patents
Warning Regarding the Use of NI Products
Technical Support and Professional Services
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Glossary

Prefixes

Prefix Meaning Value
n nano 10-9
µ micro 10-6
m milli 10-3
k kilo 103
M mega 106


Numbers/Symbols

Symbols Meaning
% percent
+ positive of, or plus
negative of, or minus
&#937 ohm
º degree

A

ADC Analog-to-digital converter—an electronic device, often an integrated circuit, that converts an analog signal to a digital value.
ADE Application development environment—some examples include LabVIEW and LabWindows/CVI.
AI Analog input—acquisition of data.
amplification A type of signal conditioning that improves accuracy in the resulting digitized signal by increasing signal amplitude relative to noise.
analog Data represented by continuously variable physical quantities.
AO Analog output—generation of data.
API Application programming interface—A library of functions, classes or VIs, attributes, and properties for creating applications for your device.
asynchronous
  1. Hardware—A signal that occurs or is acted upon at an arbitrary time, without synchronization to another signal, such as a reference clock.
  2. Software—A function that begins an operation and returns prior to the completion or termination of the operation.
attenuation The reduction of a voltage or acoustical pressure. Measured referenced to the original voltage.

B

bandwidth The range of frequencies present in a signal, or the range of frequencies to which a measuring device can respond.
bipolar A signal range that includes both positive and negative values (for example, –5 V to +5 V).
bit The smallest unit of data used in a digital operation. Bits are binary, so they can be either a 1 or a 0.
buffer In software, temporary storage for acquired or to-be-generated samples.

C

CH Channel.
channel
  1. Physical—a terminal or pin at which you can measure or generate an analog or digital signal. A single physical channel can include more than one terminal, as in the case of a differential analog input channel or a digital port of eight lines. The name used for a counter physical channel is an exception because that physical channel name is not the name of the terminal where the counter measures or generates the digital signal.
  2. Virtual—a collection of property settings that can include a name, a physical channel, input terminal connections, the type of measurement or generation, and scaling information. You can define NI-DAQmx virtual channels outside a task (global) or inside a task (local). Configuring virtual channels is optional in Traditional NI-DAQ and earlier versions, but is integral to every measurement you take in NI-DAQmx. In Traditional NI-DAQ, you configure virtual channels in MAX. In NI-DAQmx, you can configure virtual channels either in MAX or in a program, and you can configure channels as part of a task or separately.
  3. Switch—a switch channel represents any connection point on a switch. It may be made up of one or more signal wires (commonly one, two, or four), depending on the switch topology. A virtual channel cannot be created with a switch channel. Switch channels may be used only in the NI-DAQmx Switch functions and VIs.
clock A periodic digital signal.
CMRR Common-mode rejection ratio—a measure of the ability of an instrument to reject interference from a common-mode signal, usually expressed in decibels (dB).
code width The smallest detectable change in an input voltage of a DAQ device.
cold-junction compensation A method of compensating for inaccuracies in thermocouple circuits.
counter/timer A circuit that counts digital edges. Counters and timers usually have from 16 bits to 48 bits (sometimes more) counting capability. The total number of counts possible equals 2N, where N is the number of bits in the counter. When the edges counted are produced by a clock, elapsed time can be computed from the number of edges counted if the clock frequency is known.
custom scale A method of instructing NI-DAQmx to apply additional scaling to your data. Refer to the Create Scale function in your reference help.

D

DAC Digital-to-analog converter—an electronic device, often an integrated circuit, that converts a digital number into a corresponding analog voltage or current.
DAQ Refer to data acquisition.
DAQ Assistant A graphical interface for configuring measurement tasks, channels, and scales.
DAQ device A device that acquires or generates data and can contain multiple channels and conversion devices. DAQ devices include plug-in devices, PCMCIA cards, and DAQPad devices, which connect to a computer USB or 1394 (FireWire) port. SCXI modules are considered DAQ devices.
data Samples.
data acquisition
  1. Acquiring and measuring analog or digital electrical signals from sensors, acquisition transducers, and test probes or fixtures.
  2. Generating analog or digital electrical signals.
dB Decibel—the unit for expressing a logarithmic measure of the ratio of two signal levels: dB=20log10 V1/V2, for signals in volts.
DC Direct current.
delay from sample The amount of time to wait after receiving a sample clock edge before beginning the acquisition of a sample.
delay from start The amount of time to wait after receiving a start trigger before beginning the operation.
device
  1. An instrument or controller you can access as a single entity that controls or monitors real-world I/O points. A device often is connected to a host computer through some type of communication network.
  2. See also DAQ device and measurement device.
digital A TTL signal. Refer to edge.
DIO Digital input/output.
DMA Direct Memory Access—A method of transferring data between a buffer and a device that is used most often for high-speed operations.
driver Software unique to the device or type of device, and includes the set of commands the device accepts.

E

E Series A standard architecture for instrumentation-class, multichannel data acquisition devices.
edge A digital edge is a single rising or falling TTL transition. An analog edge is defined by the slope, level, and hysteresis settings.
event A digital signal produced from a device or circuit.
excitation Supplying a voltage or current source to energize an active sensor or circuit.

F

fall time The time for a signal to transition from 90% to 10% of the maximum signal amplitude.
filtering A type of signal conditioning that you can use to remove unwanted frequency components from the signal you are measuring.
FIFO A type of memory that implements a First In First Out strategy in which samples are removed in the order they were written. FIFOs are typically used as intermediate buffers between an ADC or DAC and the memory buffer.
floating signal sources Signal sources with voltage signals that are not connected to an absolute reference or system ground.

G

gain The factor by which a signal is amplified, often expressed in dB. Gain as a function of frequency is commonly referred to as the magnitude of the frequency response function.
grounded signal sources Signal sources with voltage signals that are referenced to a system ground, such as the earth or a building ground. Grounded signal sources are also called referenced signal sources.

H

hardware triggering A form of triggering in which the source of the trigger is an analog or digital signal. Refer to Software Triggering.
hysteresis A window around a trigger level that is often used to reduce false triggering due to noise or jitter in the signal.
Hz Hertz—cycles per second of a periodic signal.

I

instrument driver Refer to driver.
interrupts A method whereby a device notifies the computer of some condition on the device that requires the computer's attention. When this condition is a request for data or a notification of available data, interrupts are used as a data transfer mechanism.
I/O Input/output—the transfer of data to/from a computer system involving communications channels, operator interface devices, and/or data acquisition and control interfaces.
isolation A type of signal conditioning in which you isolate the transducer signals from the computer. Isolation makes sure the measurements from the measurement device are not affected by differences in ground potentials.

L

LED Light-emitting diode—a semiconductor light source.
line An individual signal in a digital port. The difference between a bit and a line is that the bit refers to the actual data transferred, and the line refers to the hardware the bit is transferred on. However, the terms line and bit are fairly interchangeable. For example, an 8-bit port is the same as a port with eight lines.
linearization A type of signal conditioning in which software linearizes the voltage levels from transducers, so the voltages can be scaled to measure physical phenomena.
LSB Least significant bit—often used to refer to the smallest voltage change detectable by an A/D converter or the smallest voltage change that can be generated by a D/A converter.

M

Measurement & Automation Explorer (MAX) A centralized configuration environment that allows you to configure all of your National Instruments devices.
measurement device DAQ devices such as the E Series multifunction I/O (MIO) devices, SCXI signal conditioning modules, and switch modules.
memory buffer Refer to buffer.
memory mapping A technique for reading and writing to a device directly from your program, which avoids the overhead of delegating the reads and writes to kernel-level software. Delegation to the kernel is safer, but slower. Memory mapping is less safe because an entire 4 KB page of memory must be exposed to your program for this to work, but it is faster.
MIO Multifunction I/O—Designates a family of data acquisition devices that have multiple analog input channels, digital I/O channels, timing, and optionally, analog output channels. An MIO product can be considered a miniature mixed signal tester, due to its broad range of signal types and flexibility. It is also known as multifunction DAQ. An E Series device is an example of an MIO device.
module A board assembly and its associated mechanical parts, front panel, optional shields, and so on. A module contains everything required to occupy one or more slots in a mainframe. SCXI and PXI devices are modules.
multiplexer A switching device with multiple terminals that sequentially connects each of its terminals to a single terminal, typically at high speeds. Often used to measure several signals with a single analog input channel.

N

NI-DAQ Driver software included with all NI measurement devices. NI-DAQ is an extensive library of functions you can call from an application development environment (ADE), such as LabVIEW, to program all the features of an NI measurement device, such as configuring, acquiring and generating data from, and sending data to the device.
NI-DAQmx The latest NI-DAQ driver with new functions and development tools for controlling measurement devices. The advantages of NI-DAQmx over earlier versions of NI-DAQ include the DAQ Assistant for configuring channels and measurement tasks for your device for use in LabVIEW, LabWindows/CVI, and Measurement Studio; increased performance such as faster single-point analog I/O; and a simpler API for creating DAQ applications using fewer functions than earlier versions of NI-DAQ.
nonlinearity A measure in percentage of full-scale range (FSR) of the worst-case deviation from the ideal transfer function—a straight line.
This specification is included only for DAQ products, such as signal conditioning products, that do not have an ADC. Because a product with this specification can also be used with a DAQ product with an ADC, this nonlinearity specification must be added to the relative accuracy specification of the DAQ product with the ADC.
NRSE Nonreferenced single-ended mode—all measurements are made with respect to a common (NRSE) measurement system reference, but the voltage at this reference can vary with respect to the measurement system ground.

O

onboard Provided by the data acquisition device.
onboard channels Channels provided by the plug-in data acquisition device.
onboard clock The default source for a particular clock. Usually, the device has dedicated a circuit for producing this signal and its only purpose is to act as the source for a certain clock.
onboard memory Memory provided by a device for temporary storage of input or output data. Typically, onboard memory is a FIFO, which is distinct from computer memory.

P

parallel mode A type of SCXI operating mode in which the module sends each of its input channels directly to a separate analog input channel of the device connected to the module.
pattern I/O Pattern input and output—a digital I/O operation on which a clock signal initiates a digital transfer. Because the clock signal is a constant frequency, you can generate and receive patterns at a constant rate.
PCI Peripheral Component Interconnect—a high-performance expansion bus architecture originally developed by Intel to replace ISA and EISA. PCI has achieved widespread acceptance as a standard for PCs and work stations, and it offers a theoretical maximum transfer rate of 132 Mbytes/s.
PFI Programmable Function Interface—general purpose input terminals, fixed purpose output terminals. The name of the fixed output signal is often placed on the I/O connector next to the terminal as a hint.
physical channel Refer to channel.
pin Refer to terminal.
Poisson's Ratio The negative ratio of the strain in the transverse direction (perpendicular to the force) to the strain in the axial direction (parallel to the force).
port A collection of digital lines. Usually the lines are grouped into either a 8-bit or 32-bit port. Most E Series devices have one 8-bit port.
port width The number of lines in a port. For example, most E Series devices have one port with eight lines; therefore, the port width is eight.
postrigger samples If there is no reference trigger, posttrigger samples are the data acquired after the task is started. If there is a reference trigger, this is the data acquired after the reference trigger.
pretrigger samples Data acquired before the occurrence of the reference trigger.
pretriggering The technique used on a measurement device to keep a circular buffer filled with samples, so that when the reference trigger conditions are met, the buffer includes samples leading up to the trigger condition as well as samples acquired immediately after the trigger.
programmed I/O A data transfer mechanism in which a buffer is not used and instead, the computer reads and writes directly to the device.
propagation delay The amount of time required for a signal to pass through a circuit.
pulsed output A form of counter signal generation by which a pulse is generated when a counter reaches a certain value.
PXI PCI eXtensions for Instrumentation—a rugged, open system for modular instrumentation based on CompactPCI, with special mechanical, electrical, and software features. The PXI standard was originally developed by National Instruments in 1997 and is now managed by the PXI Systems Alliance.
PXI trigger bus The timing bus that connects PXI DAQ devices directly, by means of connectors built into the backplane of the PXI chassis, for precise synchronization of functions. This bus is functionally equivalent to the RTSI bus for PCI DAQ devices.

R

range The minimum and maximum analog signal levels that the ADC can digitize.
raw Data that has not been changed in any way. For input, data is returned exactly as received from the device. For output, data is written as is to the device. Refer to unscaled and scaled.
referenced signal source Signal sources with voltage signals that are referenced to a system ground, such as the earth or a building ground. Also called grounded signal sources.
resolution The smallest amount of input signal change that a device or sensor can detect. The term discrimination is also used for resolution.
rise time The time for a signal to transition from 10% to 90% of the maximum signal amplitude.
route A connection between a pair of terminals. Any time the source or destination terminal of a signal is specified, a route is created.
RSE Referenced single-ended mode—all measurements are made with respect to a common reference measurement system or a ground. Also called a grounded measurement system.
RTD Resistance temperature detector—a metallic probe that measures temperature based on its coefficient of resistivity.
RTSI bus Real-time system integration bus—the NI timing bus that connects DAQ devices directly, by means of connectors on top of the devices, for precise synchronization of functions. This bus is functionally equivalent to the PXI Trigger bus for PXI DAQ devices.

S

s Seconds.
S Samples. Refer to sample.
S/s Samples per second—used to express the rate at which a measurement device samples an analog signal.
sample A sample is a single measurement from a single channel or, for output, a single generation to a single channel. A device may produce more than one sample per channel upon receiving a single digital edge of a sample clock. An E Series device, for example, produces one sample from each analog input channel in its task for every sample clock edge.
sample clock The clock controlling the time interval between samples. Each time the Sample Clock ticks (produces a pulse) one sample per channel is acquired or generated.
sample clock rate The number of samples per channel per second. For example, a sample clock rate of 10 S/s means sampling each channel 10 times per second.
scaled Data that has been mathematically transformed into engineering units. Other manipulations also can be done such as reordering to match the channel order.
scanning Method of sequentially connecting channels.
SCXI Signal Conditioning eXtensions for Instrumentation—the NI product line for conditioning low-level signals within an external chassis near sensors so that only high-level signals are sent to measurement devices in the noisy PC environment. SCXI is an open standard available for all vendors.
sensor A device that responds to a physical stimulus (heat, light, sound, pressure, motion, flow, and so on) and produces a corresponding electrical signal.
signal A means of conveying information. An analog waveform, a clock, and a single digital (TTL) edge are all examples of signals.
signal conditioning The manipulation of signals to prepare them for digitizing.
software trigger A function that, when it executes, triggers an action such as starting an acquisition.
source impedance A parameter of signal sources that reflects current-driving ability of voltage sources (lower is better) and the voltage-driving ability of current sources (higher is better).
STC System timing controller.
synchronous
  1. Hardware—a signal that occurs or is acted upon in synchrony with another signal, such as a reference clock.
  2. Software—a function that begins an operation and returns only when the operation is complete.

T

task A collection of one or more channels, timing, and triggering and other properties that apply to the task itself. Conceptually, a task represents a measurement or generation you want to perform.
task buffer Refer to buffer.
terminal A named location on a DAQ device where a signal is either generated (output or produced) or acquired (input or consumed).
terminal count When counting up, an N bit counter reaches its terminal count at 2N -1. An N bit counter counting down reaches its terminal count at 0.
thermistor A semiconductor sensor that produces a repeatable change in electrical resistance as a function of temperature. Most thermistors have a negative temperature coefficient.
thermocouple A temperature sensor created by joining two dissimilar metals. The junction produces a small voltage as a function of the temperature.
threshold The voltage level a signal must reach for a trigger to occur.
tick A digital edge of a clock.
timebase A clock that is divided down to produce another clock or a clock provided to a counter for measuring elapsed time.
transducer Refer to sensor.
Traditional NI-DAQ (Legacy) An upgrade of the earlier version of NI-DAQ. Traditional NI-DAQ (Legacy) has the same VIs and functions and works the same way as NI-DAQ 6.9.x, except you can use both Traditional NI-DAQ (Legacy) and NI-DAQmx on the same computer, and some hardware is no longer supported.
transducer excitation A type of signal conditioning that uses external voltages and currents to excite the circuitry of a signal conditioning system into measuring physical phenomena.
trigger Any signal that causes a device to perform an action, such as starting an acquisition.
TTL Transistor-transistor logic—a signal having two discrete levels, a high and a low level.

U

unipolar A signal range that is always positive (for example, 0 to +10 V).
unscaled Samples in the integer form that the hardware produces or requires. Although no mathematical transformations are applied to unscaled data, other manipulations may be done such as reordering to match the channel order.

V

V Volts.
virtual channel Refer to channel.
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