National Instruments DAQ X Series, Руководство пользователя

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Glossary
© National Instruments G-5 X Series User Manual
D
DAC Digital-to-Analog Converter—An electronic device, often an integrated
circ
u it, that converts a digital n u mber into a corresponding analog voltage
or c u rrent.
In the instr u mentation world, DACs can be u sed to generate arbitrary
waveform shapes, defined by the software algorithm that comp u tes the
digital data pattern, which is fed to the DAC.
DAQ 1. Data acq u isition—The process of collecting and meas u ring electrical
signals from sensors, transd u cers, and test probes or fixt u res and
inp u tting them to a comp u ter for processing.
2. Data acq u isition—The process of collecting and meas u ring the same
kinds of electrical signals with A/D and/or DIO devices pl u gged into a
comp u ter, and possibly generating control signals with D/A and/or
DIO devices in the same comp u ter.
DAQ device A device that acq u ires or generates data and can contain m u ltiple channels
and conversion devices. DAQ devices incl u de pl u g-in devices, PCMCIA
cards, and DAQPad devices, which connect to a comp u ter USB port. SCXI
mod u les are considered DAQ devices.
DAQ-STC3 Third generation data acq u isition system timing controller chip.
data acq u isition The general concept of acq u iring data, as in begin data acq u isition or data
acq u isition and control. See also DAQ.
data transfer A techniq u e for moving digital data from one system to another.
Options for data transfer are DMA 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 acq
u ire a single data point. DMA
transfers u se a DMA controller, instead of the CPU, to move acq u ired data
from the device into comp u ter memory. Even tho u gh high-speed data
transfers can occ u r with programmed I/O transfers, they req u ire the u se of
the CPU to transfer data. DMA transfers are able to acq u ire data at high
speeds and keep the CPU free for performing other tasks at the same time.
dB Decibel—The u nit for expressing a logarithmic meas u re of the ratio of
two signal levels: dB = 20log10 V1/V2, for signals in volts.
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