Glossary
G-2
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D
DAQ
Data acquisition. (1) Collecting and measuring electrical signals from
sensors, transducers, and test probes or fixtures and inputting them to a
computer for processing. (2) Collecting and measuring the same kinds of
electrical signals with A/D or DIO boards plugged into a computer, and
possibly generating control signals with D/A and/or DIO boards in the
same computer.
DMA
Direct memory access. A method by which data can be transferred between
computer memory and a device or memory on the bus while the processor
does something else. DMA is the fastest method of transferring data
to/from computer memory.
driver
Software that controls a specific hardware device, such as an IMAQ or
DAQ device.
E
external trigger
A voltage pulse from an external source that triggers an event such as
A/D conversion.
F
field
For an interlaced video signal, a field is half the number of horizontal lines
needed to represent a frame of video. The first field of a frame contains all
the odd-numbered lines, the second field contains all of the even-numbered
lines.
frame
A complete image. In interlaced formats, a frame is composed of two fields.
G
gamma
The nonlinear change in the difference between the video signal’s
brightness level and the voltage level needed to produce that brightness.
genlock
The process of synchronizing a video source to the signal from a separate
video source. The circuitry aligns the video timing signals by locking
together the horizontal, vertical, and color subcarrier frequencies and
phases and generates a pixel clock that clocks pixel data into memory for
display or into another circuit for processing.
