National Instruments USB-621 Series User Manual page 181

Glossary
channel
clock
CMOS
CMRR
common-mode
rejection
common-mode
signal
convert rate
count
counter
counter/timer
NI USB-621x User Manual
Pin or wire lead to which you apply or from which you read the analog or
digital signal. Analog signals can be single-ended or differential. For digital
signals, you group channels to form ports. Ports usually consist of either
four or eight digital channels.
Hardware component that controls timing for reading from or writing to
groups.
Complementary metal-oxide semiconductor.
Common-mode rejection ratio—A measure of the ability of a differential
amplifier to reject interference from a common-mode signal, usually
expressed in decibels (dB).
The ability of an electronic system to cancel any electronic noise pick-up
that is common to both the positive and negative polarities of the input leads
to the instrument front end. Common mode rejection is only a relevant
specification for systems having a balanced or differential input.
1. Any voltage present at the instrumentation amplifier inputs with
respect to amplifier ground.
2. The signal, relative to the instrument chassis or computer's ground, of
the signals from a differential input. This is often a noise signal, such
as 50 or 60 Hz hum.
Reciprocal of the interchannel delay.
The number of events, such as zero crossings, pulses, or cycles.
1. Software. A memory location used to store a count of certain
occurrences.
2. Hardware. A circuit that counts events. When it refers to an instrument,
it refers to a frequency counter.
A circuit that counts external pulses or clock pulses (timing).
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