Glossary
NI USB-621x User Manual G-6 ni.com
differential input An input circuit that actively responds to the difference between two
terminals, rather than the difference between one terminal and ground.
Often associated with balanced input circuitry, but also may be used with
an unbalanced source.
digital I/O The capability of an instrument to generate and acquire digital signals.
Static digital I/O refers to signals where the values are set and held, or
rarely change. Dynamic digital I/O refers to digital systems where the
signals are continuously changing, often at multi-MHz clock rates.
digital signal A representation of information by a set of discrete values according to a
prescribed law. These values are represented by numbers.
digital trigger A TTL level signal having two discrete levels—A high and a low level.
DIO Digital input/output.
driver Software unique to the device or type of device, and includes the set of
commands the device accepts.
E
edge detection A technique that locates an edge of an analog signal, such as the edge of a
square wave.
EEPROM Electrically Erasable Programmable Read-Only Memory—ROM that can
be erased with an electrical signal and reprogrammed. Some SCXI modules
contain an EEPROM to store measurement-correction coefficients.
encoder A device that converts linear or rotary displacement into digital or pulse
signals. The most popular type of encoder is the optical encoder, which uses
a rotating disk with alternating opaqu e areas, a light source, and a
photodetector.
external trigger A voltage pulse from an external source that causes a DAQ operation to
begin.
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