National Instruments Image Acquisition Software - Manual (Page 61)

Glossary
NI-IMAQ User Manual G-10 © National Instruments Corporation
PCLKIN pixel clock in signal
PFI programmable function input
PGIA programmable gain instrumentation amplifier
picture aspect ratio the ratio of the active pixel region to the active line region; for standard
video signals like RS-170 or CCIR, the full-size picture aspect ratio
normally is 4/3 (1.33)
pixel picture element—the smallest division that makes up the video scan line;
for display on a computer monitor, a pixel’s optimum dimension is square
(aspect ratio of 1:1, or the width equal to the height)
pixel aspect ratio the ratio between the physical horizontal size and the vertical size of the
region covered by the pixel; an acquired pixel should optimally be square,
thus the optimal value is 1.0, but typically it falls between 0.95 and 1.05,
depending on camera quality
pixel clock divides the incoming horizontal video line into pixels
pixel count the total number of pixels between two HYSNCs; the pixel count
determines the frequency of the pixel clock
PLL phase-locked loop—circuitry that provides a very stable pixel clock that is
referenced to another signal, for example, an incoming HSYNC signal
protocol the exact sequence of bits, characters, and control codes used to transfer
data between computers and peripherals through a communications
channel
pts points
R
RAM random-access memory
real time a property of an event or system in which data is processed as it is acquired
instead of being accumulated and processed at a later time
relative accuracy a measure in LSB of the accuracy of an ADC; it includes all nonlinearity
and quantization errors but does not include offset and gain errors of the
circuitry feeding the ADC
UM.book Page 10 Monday, July 13, 1998 9:49 AM