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PCI-4451/4452 User Manual G-6
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National Instruments Corporation
delta-sigma modulating
ADC
a high-accuracy circuit that samples at a higher rate and lower resolution
than is needed and (by means of feedback loops) pushes the quantization
noise above the frequency range of interest. This out-of-band noise is
typically removed by digital filters.
device a plug-in data acquisition board, card, or pad that can contain multiple
channels and conversion devices. Plug-in boards, PCMCIA cards, and
devices such as the DAQPad-1200, which connects to your computer
parallel port, are all examples of DAQ devices. SCXI modules are distinct
from devices, with the exception of the SCXI-1200, which is a hybrid.
DIFF differential mode
differential input an analog input consisting of two terminals, both of which are isolated from
computer ground, whose difference is measured
differential measurement
system
a way you can configure your device to read signals, in which you do not
need to connect either input to a fixed reference, such as the earth or a
building ground
digital port See port.
digital trigger a TTL level signal having two discrete levels—a high and a low level
DIO digital input/output
DMA direct memory access—a method by which data can be transferred to/from
computer memory from/to 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.
DNL differential nonlinearity—a measure in least significant bit of the
worst-case deviation of code widths from their ideal value of 1 LSB
down counter performing frequency division on an internal signal
drivers software that controls a specific hardware device such as a DAQ board or
a GPIB interface board
dynamic range the ratio of the largest signal level a circuit can handle to the smallest signal
level it can handle (usually taken to be the noise level), normally expressed
in decibels
User.book Page 6 Tuesday, April 14, 1998 10:20 AM