National Instruments PXI NI 5401 User Manual
Page 51
Glossary
G-4
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F
FIFO
first-in first-out memory buffer—the first data stored is the first data sent to
the acceptor. FIFOs are often used on DAQ devices to temporarily store
incoming or outgoing data until that data can be retrieved or output. For
example, an analog input FIFO stores the results of A/D conversions until
the data can be retrieved into system memory, a process that requires the
servicing of interrupts and often the programming of the DMA controller.
This process can take several milliseconds in some cases. During this time,
data accumulates in the FIFO for future retrieval. With a larger FIFO,
longer latencies can be tolerated. In the case of analog output, a FIFO
permits faster update rates, because the waveform data can be stored on the
FIFO ahead of time. This again reduces the effect of latencies associated
with getting the data from system memory to the DAQ device.
filters
digital or analog circuits that change the frequency characteristics of a
waveform
frequency hop
change from one frequency to another
frequency resolution
the smallest frequency change that can be generated by a NI 5411/5431
frequency sweep
change the frequency of a waveform in a controlled manner
G
gain
the factor by which a signal is amplified, sometimes expressed in decibels
GUI
graphical user interface
H
hardware
the physical components of a computer system, such as the circuit boards,
plug-in boards, chassis, enclosures, peripherals, cables, and so on
HiZ
high impedance
Hz
hertz—the number of cycles or repetitions per second