Glossary
©
National Instruments Corporation
G-7
H
h
hour
hardware
the physical components of a computer system, such as the circuit boards,
plug-in boards, chassis, enclosures, peripherals, and cables
hardware triggering
a form of triggering where you set the start time of an acquisition and gather
data at a known position in time relative to a trigger signal
high-impedance
in logic circuits designed to have three possible states—0, 1, and hi-Z—the
hi-Z (high impedance) state effectively removes the output from its circuit,
and can be used to simplify bus communication by wire-ANDing tri-state
inputs
Hz
hertz—cycles per second. Specifically refers to the repetition frequency of
a waveform.
I
I/O
input/output—the transfer of data to/from a computer system involving
communications channels, operator interface devices, and/or data
acquisition and control interfaces
IEPE
Integral Electronics Piezoelectric, also known as integrated circuit
piezoelectric—a type of transducer that operates using a constant current
source as the conditioning medium and returns a signal in the form of
voltage modulation on the same line as the current source
IMD
intermodulation distortion—the ratio, in dB, of the total rms signal level of
harmonic sum and difference distortion products, to the overall rms signal
level. The test signal is two sine waves added together according to the
following standards:
CCIF—A 14 kHz sine wave and a 15 kHz sine wave added in a
1:1 amplitude ratio.
in.
inches
INL
integral nonlinearity—a measure in LSB of the worst-case deviation from
the ideal A/D or D/A transfer characteristic of the analog I/O circuitry
input impedance
the measured resistance and capacitance between the input terminals of a
circuit and ground
