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Glossary
Numbers/Symbols
1D
2D
A
A
AC
A/D
ADC
ADC resolution
AI
AIGND
Prefix n-
µ
mk-
M-
Meaning nanomicromillikilomega-
Value
10-9
10-6
10-3
103
106
One-dimensional.
Two-dimensional. amperes.
Alternating current.
Analog-to-digital.
Analog-to-digital converter. An electronic device, often an integrated circuit, that converts an analog voltage to a digital number.
The resolution of the ADC, which is measured in bits. An ADC with 16 bits has a higher resolution, and thus a higher degree of accuracy than a 12-bit ADC.
Analog input.
The analog input ground pin on a DAQ device.
National Instruments Corporation G-1 LabVIEW Data Acquisition Basics Manual
Glossary amplification
AMUX devices analogin analog_io.llb
analog input group analog multiplexer analogout.llb
analog output group analog trigger
A type of signal conditioning that improves accuracy in the resulting digitized signal and to reduce noise.
See analog multiplexers .
A LabVIEW DAQ library containing VIs that perform analog input with DAQ devices and SCXI modules and can write or stream the acquired data to disk.
A LabVIEW DAQ library containing VIs for analog I/O control loops.
A collection of analog input channels. You can associate each group with its own clock rates, trigger and buffer configurations, and so on. A channel cannot belong to more than one group.
Because each board has one ADC, only one group can be active at any given time. That is, once a control VI starts a timed acquisition with group n , subsequent control and read calls must also refer to group n . You use the task ID to refer to the group.
Devices that increase the number of measurement channels while still using an single instrumentation amplifier. Also called AMUX devices.
A LabVIEW DAQ library containing VIs that generate single values or multiple values (waveforms) to output through analog channels.
A collection of analog output channels. You can associate each group with its own clock rates, buffer configurations, and so on.
A channel cannot belong to more than one group.
A trigger that occurs at a user-selected point on an incoming analog signal. Triggering can be set to occur at a specified level on either an increasing or a decreasing signal (positive or negative slope).
LabVIEW Data Acquisition Basics Manual G-2 National Instruments Corporation
Glossary
AO array
B
BCD bipolar
Analog output.
Ordered, indexed set of data elements of the same type.
Binary-coded decimal.
A signal range that includes both positive and negative values
(for example, -5 to 5 V).
Temporary storage for acquired or generated data. buffer
C
cascading channel channel clock circular-buffered I/O clock cluster code width column-major order
National Instruments Corporation
Process of extending the counting range of a counter chip by connecting to the next higher counter.
Pin or wire lead to which you apply or from which you read the analog or digital signal. Analog signals can be single-ended or differential. For digital signals, you group channels to form ports.
Ports usually consist of either four or eight digital channels.
The clock controlling the time interval between individual channel sampling within a scan. Boards with simultaneous sampling do not have this clock.
Input/output operation that reads or writes more data points than can fit in the buffer. When LabVIEW reaches the end of the buffer, LabVIEW returns to the beginning of the buffer and continues to transfer data.
Hardware component that controls timing for reading from or writing to groups.
A set of ordered, unindexed data elements of any data type including numeric, Boolean, string, array, or cluster. The elements must be all controls or all indicators.
The smallest detectable change in an input voltage of a DAQ device.
A way to organize the data in a 2D array by columns.
G-3 LabVIEW Data Acquisition Basics Manual
Glossary common-mode voltage conditional retrieval conversion device counter.llb
counter/timer group coupling
D
D/A
DAC
Any voltage present at the instrumentation amplifier inputs with respect to amplifier ground.
A method of triggering in which you to simulate an analog trigger using software. Also called software triggering .
Device that transforms a signal from one form to another. For example, analog-to-digital converters (ADCs) for analog input, digital-to-analog converters (DACs) for analog output, digital input or output ports, and counter/timers are conversion devices.
A LabVIEW DAQ library containing VIs that count the rising and falling edges of TTL signals, generate TTL pulses, and measure the frequency and period of TTL signals.
A collection of counter/timer channels. You can use this type of group for simultaneous operation of multiple counter/timers.
The manner in which a signal is connected from one location to another. daqconf data acquisition data flow default input
Digital-to-analog.
Digital-to-analog converter. An electronic device, often an integrated circuit, that converts a digital number into a corresponding analog voltage or current.
The NI-DAQ configuration utility on the Sun.
Process of acquiring data, typically from A/D or digital input plug-in boards.
Programming system consisting of executable nodes in which nodes execute only when they have received all required input data and produce output automatically when they have executed.
LabVIEW is a dataflow system.
The default value of a front panel control.
LabVIEW Data Acquisition Basics Manual G-4 National Instruments Corporation
Glossary default setting device device number
DIFF differential measurement system digital digital input group digital output group digital trigger
DIP
National Instruments Corporation
A default parameter value recorded in the driver. In many cases, the default input of a control is a certain value (often 0) that means use the current default setting . For example, the default input for a parameter may be do not change current setting , and the default setting may be no AMUX-64T boards . If you do change the value of such a parameter, the new value becomes the new setting. You can set default settings for some parameters in the configuration utility.
A DAQ device inside your computer or attached directly to your computer through a parallel port. Plug-in boards, PCMCIA cards, and devices such as the DAQPad-1200, which connects to your computer's parallel port, are all examples of DAQ devices. SCXI modules are distinct from devices, with the exception of the
SCXI-1200, which is a hybrid.
The slot number or board ID number assigned to the board when you configured it. \
Differential. A differential input is an analog input consisting of two terminals, both of which are isolated from computer ground and whose difference you measure.
A way you can configure your device to read signals, in which you do not need to connect either input to a fixed reference, such as the earth or a building ground.
A LabVIEW DAQ library containing VIs that perform immediate digital I/O and digital handshaking with DAQ devices and SCXI modules .
A collection of digital input ports. You can associate each group with its own clock rates, handshaking modes, buffer configurations, and so on. A port cannot belong to more than one group.
A collection of digital output ports. You can associate each group with its own clock rates, handshaking modes, buffer configurations, and so forth. A port cannot belong to more than one group.
A TTL level signal having two discrete levels—a high and a low level.
Dual inline package.
G-5 LabVIEW Data Acquisition Basics Manual
Glossary dithering
DLL
DMA down counter driver
DSP
E
EEPROM
The addition of Gaussian noise to an analog input signal.
Dynamic link library.
Direct memory access. A method by which data you can transfer data to computer memory from a device or memory on the bus (or from computer memory to a device) while the processor does something else. DMA is the fastest method of transferring data to or from computer memory.
Performing frequency division on an internal signal.
Software that controls a specific hardware device, such as a data acquisition board.
Digital signal processing.
EISA event external trigger
F
FIFO filtering floating signal sources
LabVIEW Data Acquisition Basics Manual
Electrically erased programmable read-only memory. Read-only memory that you can erase with an electrical signal and reprogram.
Extended Industry Standard Architecture.
The condition or state of an analog or digital signal.
A voltage pulse from an external source that triggers an event such as A/D conversion.
A first-in-first-out memory buffer. In a FIFO, the first data stored is the first data sent to the acceptor.
A type of signal conditioning that allows you to filter unwanted signals from the signal you are trying to measure.
Signal sources with voltage signals that are not connected to an absolute reference or system ground. Also called nonreferenced signal sources. Some common example of floating signal sources are batteries, transformers, or thermocouples.
G-6 National Instruments Corporation
Glossary
G
gain
GATE input pin
The amplification or attenuation of a signal.
A counter input pin that controls when counting in your application occurs.
grounded measurement system See referenced single-ended measurement system .
grounded signal sources Signal sources with voltage signals that are referenced to a system ground, such as the earth or a building ground. Also called referenced signal sources group A collection of input or output channels or ports that you define.
Groups can contain analog input, analog output, digital input, digital output, or counter/timer channels. A group can contain only one type of channel, however. You use a task ID number to refer to a group after you create it. You can define up to 16 groups at one time.
To erase a group, you pass an empty channel array and the group number to the group configuration VI. You do not need to erase a group to change its membership. If you reconfigure a group whose task is active, LabVIEW clears the task and returns a warning. LabVIEW does not restart the task after you reconfigure the group.
H
handle handshaked digital I/O hardware triggering hex
Hz
National Instruments Corporation
Pointer to a pointer to a block of memory; handles reference arrays and strings. An array of strings is a handle to a block of memory containing handles to strings.
A type of digital acquisition/generation where a device or module accepts or transfers data after a digital pulse has been received.
Also called latched digital I/O .
A form of triggering where you set the start time of an acquisition and gather data at a known position in time relative to a trigger signal.
Hexadecimal.
Hertz. The number of scans read or updates written per second.
G-7 LabVIEW Data Acquisition Basics Manual
Glossary
I
IEEE immediate digital I/O input limits input range interrupt interval scanning
I/O
Institute of Electrical and Electronic Engineers.
A type of digital acquisition/generation where LabVIEW updates the digital lines or port states immediately or returns the digital value of an input line. Also called nonlatched digital I/O .
The upper and lower voltage inputs for a channel. You must use a pair of numbers to express the input limits. The VIs can infer the input limits from the input range, input polarity, and input gain(s). Similarly, if you wire the input limits, range, and polarity, the VIs can infer the onboard gains when you do not use
SCXI.
The difference between the maximum and minimum voltages an analog input channel can measure at a gain of 1. The input range is a scalar value, not a pair of numbers. By itself the input range does not uniquely determine the upper and lower voltage limits.
An input range of 10 V could mean an upper limit of +10 V and a lower of 0 V or an upper limit of +5 V and a lower limit of -5 V.
The combination of input range, polarity, and gain determines the input limits of an analog input channel. For some boards, jumpers set the input range and polarity, while you can program them for other boards. Most boards have programmable gains. When you use SCXI modules, you also need their gains to determine the input limits.
A signal indicating that the central processing unit should suspend its current task to service a designated activity.
Scanning method where there is a longer interval between scans than there is between individual channels comprising a scan.
Input/output. The transfer of data to or from a computer system involving communications channels, operator interface devices, and/or data acquisition and control interfaces.
LabVIEW Data Acquisition Basics Manual G-8 National Instruments Corporation
Glossary
ISA isolation
Industry Standard Architecture.
A type of signal conditioning in which you isolate the transducer signals from the computer for safety purposes. This protects you and your computer from large voltage spikes and makes sure the measurements from the DAQ device are not affected by differences in ground potentials.
K
Kwords 1,024 words of memory.
L
LabVIEW latched digital I/O limit settings
Laboratory Virtual Instrument Engineering Workbench.
A type of digital acquisition/generation where a device or module accepts or transfers data after a digital pulse has been received.
Also called handshaked digital I/O .
The maximum and minimum voltages of the analog signals you are measuring or generating.
linearization A type of signal conditioning in which LabVIEW linearizes the voltage levels from transducers, so the voltages can be scaled to measure physical phenomena.
LSBLeast significant bit.
M
MBmegabytes of memory. memory buffer See buffer. multibuffered I/O Input operation for which you allocate more than one memory buffer so you can read and process data from one buffer while the acquisition fills another.
National Instruments Corporation G-9 LabVIEW Data Acquisition Basics Manual
Glossary multiplexed mode multiplexer
An SCXI operating mode in which analog input channels are multiplexed into one module output so that your cabled DAQ device has access to the module’s multiplexed output as well as the outputs on all other multiplexed modules in the chassis through the SCXI bus. Also called serial mode .
A set of semiconductor or electromechanical switches with a common output that can select one of a number of input signals and that you commonly use to increase the number of signals measured by one ADC.
N
NI-DAQ
NI-PNP.EXE
NI-PNP.INI
nodes
The NI-DAQ configuration utility on the Macintosh.
A stand-alone executable that NI-DAQ installs in your NI-DAQ root drive that detects and configures any Plug and Play devices you have in your computer.
A file, generated by the NI-PNP.EXE
, that contains information about all the National Instruments devices in your computer, including Plug and Play devices.
Execution elements of a block diagram consisting of functions, structures, and subVIs.
nonlatched digital I/O A type of digital acquisition/generation where LabVIEW updates the digital lines or port states immediately or returns the digital value of an input line. Also called immediate digital I/O .
non-referenced signal sources Signal sources with voltage signals that are not connected to an absolute reference or system ground. Also called floating signal sources. Some common example of non-referenced signal sources are batteries, transformers, or thermocouples.
NRSE Nonreferenced single-ended.
Non-referenced single-ended 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.
LabVIEW Data Acquisition Basics Manual G-10 National Instruments Corporation
Glossary
O
onboard channels
OUT output pin output limits
Channels provided by the plug-in data acquisition board.
A counter output pin where the counter can generate various TTL pulse waveforms.
The upper and lower voltage or current outputs for an analog output channel. The output limits determine the polarity and voltage reference settings for a board.
P
parallel mode pattern generation
PGIA
Plug and Play devices postriggering pretriggering pulse trains pulsed output
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 to the module.
A type of handshaked (latched) digital I/O in which internal counters generate the handshaked signal, which in turn initiates a digital transfer. Because counters output digital pulses at a constant rate, this means you can generate and retrieve patterns at a constant rate because the handshaked signal is produced at a constant rate.
Programmable gain instrumentation amplifier.
Devices that do not require dip switches or jumpers to configure resources on the devices—also called switchless devices.
The technique you use on a data acquisition board to acquire a programmed number of samples after trigger conditions are met.
The technique you use on a data acquisition board to keep a continuous buffer filled with data, so that when the trigger conditions are met, the sample includes the data leading up to the trigger condition.
Multiple pulses.
A form of counter signal generation by which a pulse is outputted when a counter reaches a certain value.
National Instruments Corporation G-11 LabVIEW Data Acquisition Basics Manual
Glossary
R
read mark Points to the scan at which a read operation begins. Analogous to a file I/O pointer, the read mark moves every time you read data from an input buffer. After the read is finished, the read mark points to the next unread scan. Because multiple buffers are possible, you need both the buffer number and the scan number to express the position of the read mark. read mode referenced signal sources
Indicates one of the four reference marks within an input buffer that provides the reference point for the read. This reference can be the read mark, the beginning of the buffer, the most recently acquired data, or the trigger position.
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 .
referenced single-ended (RSE) All measurements are made with respect to a common reference measurement system or a ground. Also called a grounded measurement system .
RMS row-major order
RSE
RTD
RTSI run_me.llb
Root mean square.
A way to organize the data in a 2D array by rows.
Referenced single-ended.
Resistance temperature detector. A temperature-sensing device whose resistance increases with increases in temperature.
Real-Time System Integration bus. The National Instruments timing bus that interconnects data acquisition boards directly, by means of connectors on top of the boards, for precise synchronization of functions.
A LabVIEW DAQ VI library containing VIs that perform basic operations concerning analog I/O, digital I/O, and counters.
LabVIEW Data Acquisition Basics Manual G-12 National Instruments Corporation
Glossary
S
sample sample counter scan scan clock scan rate scan width
SCXI sec settling time signal conditioning signal divider
A single (one and only one) analog or digital input or output data point.
The clock that counts the output of the channel clock, in other words, the number of samples taken. On boards with simultaneous sampling, this counter counts the output of the scan clock and hence the number of scans.
One or more analog or digital input samples. Typically, the number of input samples in a scan is equal to the number of channels n the input group. For example, one pulse from the scan clock produces one scan which acquires one new sample from every analog input channel in the group.
The clock controlling the time interval between scans. On boards with interval scanning support (for example, the AT-MIO-16F-
5), this clock gates the channel clock on and off. On boards with simultaneous sampling (for example, the EISA-A2000), this clock clocks the track-and-hold circuitry.
The number of times (or scans) per second that LabVIEW acquires data from channels. For example, at a scan rate of 10Hz,
LabVIEW samples each channel in a group 10 times per second.
The number of channels in the channel list or number of ports in the port list you use to configure an analog or digital input group.
Signal Conditioning eXtensions for Instrumentation. The
National Instruments product line for conditional low-level signals within an external chassis near sensors, so only high-level signals in a noisy environment are sent to data acquisition boards.
Seconds.
The amount of time required for a voltage to reach its final value within specified limits.
The manipulation of signals to prepare them for digitizing.
Performing frequency division on an external signal.
National Instruments Corporation G-13 LabVIEW Data Acquisition Basics Manual
Glossary simple-buffered I/O single-ended inputs software trigger software triggering
SOURCE input pin
STC strain gauge subVI switchless device syntax
Input/output operation that uses a single memory buffer big enough for all of your data. LabVIEW transfers data into or out of this buffer at the specified rate, beginning at the start of the buffer and stopping at the end of the buffer. You use simple buffered I/O when you acquire small amounts of data relative to memory constraints.
Analog inputs that you measure with respect to a common ground.
A programmed event that triggers an event such as data acquisition.
A method of triggering in which you to simulate an analog trigger using software. Also called conditional retrieval .
An counter input pin where the counter counts the signal transitions.
System timing controller.
A thin conductor, which is attached to a material, that detects stress or vibrations in that material.
VI used in the block diagram of another VI; comparable to a subroutine.
Devices that do not require dip switches or jumpers to configure resources on the devices—also called Plug and Pla y devices.
The set of rules to which statements must conform in a particular programming language.
LabVIEW Data Acquisition Basics Manual G-14 National Instruments Corporation
Glossary
T
task task ID
TC toggled output
National Instruments Corporation
A timed I/O operation using a particular group. See task ID.
A number generated by LabVIEW, which encodes the device number and group number after you configure a group. You use the group configuration VIs in each function group to create the task ID, which you use when you run other VIs to specify the boards or channels on which the VIs operate. For example, the task ID in hex for an analog input task that uses group 2 and device 3 is 01020003. The following table shows how the configuration VIs encode the bits of the task ID.
Bits
31 through 28
27 through 24
23 through 20
19 through 16
15 through 0
Purpose
Reserved
Function code
Reserved
Group number
Device number
The following table gives the function code definitions.
Function Code
1
2
3
4
5
I/O Operation analog input analog output digital port I/O digital group I/O counter/timer I/O
Terminal count. The highest value of a counter.
A form of counter signal generation by which the output changes the state of the output signal from high to low, or low to high when the counter reaches a certain value.
G-15 LabVIEW Data Acquisition Basics Manual
V
V
VDC
VI
V ref
Glossary top-level VI track-and-hold transducer excitation trigger
U
unipolar update update rate update width
VI at the top of the VI hierarchy. This term is used to distinguish the VI from its subVIs.
A circuit that tracks an analog voltage and holds the value on command.
A type of signal conditioning that uses external voltages and currents to excite the circuitry of a signal conditioning system into measuring physical phenomena.
Any event that causes or starts some form of data capture.
A signal range that is either always positive or negative, but never both (for example 0 to 10 V, not -10 to 10 V).
One or more analog or digital output samples. Typically, the number of output samples in an update is equal to the number of channels in the output group. For example, one pulse from the update clock produces one update which sends one new sample to every analog output channel in the group.
The number of output updates per second.
The number of channels in the channel list or number of ports in the port list you use to configure an analog or digital output group.
volts.
Volts, direct current.
Virtual instrument. A LabVIEW program; so called because it models the appearance and function of a physical instrument.
Voltage reference.
LabVIEW Data Acquisition Basics Manual G-16 National Instruments Corporation
W
waveform
WDAQCONF.EXE
wire write mark
Glossary
Multiple voltage readings taken at a specific sampling rate.
The NI-DAQ configuration utility in Windows.
Data path between nodes.
Points to the update at which a write operation begins. Analogous to a file I/O pointer, the write mark moves every time you write data into an output buffer. After the write is finished, the write mark points to the next update to be written. Because multiple buffers are possible, you need both the buffer number and the update number to express the position of the write mark.
National Instruments Corporation G-17 LabVIEW Data Acquisition Basics Manual
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