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Glossary
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National Instruments Corporation G-9 AT-MIO-16X User Manual
external trigger a voltage pulse from an external source that triggers an event such as
A/D conversion
F
F farads
false triggering triggering that occurs at an unintended time
fetch-and-deposit a data transfer in which the data bytes are transferred from the source to
the controller, and then from the controller to the target
Fieldbus an all-digital communication network used to connect process
instrumentation and control systems; it will ultimately replace existing
4–20 mA analog standard
Fieldbus Foundation the organization located in Austin, TX, that is developing a standard
digital communication network (fieldbus) for industrial automation
applications. The network developed by the Foundation is referred to as
the Foundation Fieldbus.
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.
filtering a type of signal conditioning that allows you to filter unwanted signals
from the signal you are trying to measure
flash ADC an ADC whose output code is determined in a single step by a bank of
comparators and encoding logic
floating signal sources signal sources with voltage signals that are not connected to an absolute
reference or system ground. Also called nonreferenced signal sources.