National Instruments PCI-4451 用户手册

Glossary

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 National Instruments Corporation

G-9

PCI-4451/4452 User Manual

h

hour

half-power bandwidth

the frequency range over which a circuit maintains a level of at least –3 dB 
with respect to the nominal level

handshaked digital I/O

a type of digital acquisition/generation where a device or module accepts 
or transfers data after a digital pulse has been received. Also called latched 
digital I/O.

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

Hz

hertz—cycles per second. Specifically refers to the repetition frequency of 
a waveform.

IC

integrated circuit

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:

SMPTE—A 60 Hz sine wave and a 7 kHz sine wave added in a 
4:1 amplitude ratio.

DIN—A 250 Hz sine wave and an 8 kHz sine wave added in a 
4:1 amplitude ratio.

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 bias current

the current that flows into the inputs of a circuit

User.book  Page 9  Tuesday, April 14, 1998  10:20 AM