Glossary
M Series User Manual G-6 ni.com
DAQ 1. Data acquisition—The process of collecting and measuring electrical
signals from sensors, transducers, and test probes or fixtures and
inputting them to a computer for processing.
2. Data acquisition—The process of collecting and measuring the same
kinds of electrical signals with A/D and/or DIO devices plugged into a
computer, and possibly generating control signals with D/A and/or
DIO devices in the same computer.
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.
DAQ-STC2 Data acquisition system timing controller chip.
data acquisition The general concept of acquiring data, as in begin data acquisition or data
acquisition and control. See also DAQ.
data transfer A technique for moving digital data from one system to another.
Options for data transfer are DMA, interrupt, and programmed I/O. For
programmed I/O transfers, the CPU in the PC reads data from the DAQ
device whenever the CPU receives a software signal to acquire a single data
point. Interrupt-based data transfers occur when the DAQ device sends an
interrupt to the CPU, telling the CPU to read the acquired data from the
DAQ device. DMA transfers use a DMA controller, instead of the CPU, to
move acquired data from the device into computer memory. Even though
high-speed data transfers can occur with interrupt and programmed I/O
transfers, they require the use of the CPU to transfer data. DMA transfers
are able to acquire data at high speeds and keep the CPU free for
performing other tasks at the same time.
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—although the term speaks of current, many different types
of DC measurements are made, including DC Voltage, DC current, and DC
power.
device An electronic board that performs general analog or digital I/O functions
on one or multiple channels, connected to a PC through a bus or I/O port,
such as PCI, PXI, Ethernet, USB, or serial.
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