Glossary
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ni.com
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 and/or DIO devices plugged into a computer,
and possibly generating control signals with D/A and/or DIO devices in the
same computer
dB
decibel—the unit for expressing a logarithmic measure of the ratio of
two signal levels: dB = 20log
10
(V
1
/V
2
), for signals in volts
dBFS
absolute signal level compared to full scale
DC
direct current
DC coupled
allowing the transmission of both AC and DC signals
DDS clock
Direct Digital Synthesis clock—a type of clock source with an output
frequency controlled by a digital input word
default setting
a default parameter value recorded in the driver. In many cases, the default
input of a control is a certain value (often 0) that means
use the current
default setting
. For example, the default input for a parameter may be
do
not change current setting
, and the default setting may be
no AMUX-64T
devices
. If you do change the value of such a parameter, the new value
becomes the new setting. You can set default settings for some parameters
in the configuration utility or manually using switches located on the
device.
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 DAQ board, card, or pad that can contain multiple channels and
conversion devices. Plug-in boards and PCMCIA cards are all examples of
DAQ devices. SCXI modules are distinct from devices.
differential input
an analog input consisting of two terminals, both of which are isolated from
computer ground, whose difference is measured
