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floor
The part of the uncertainty specification of an instrument that is typically a fixed offset
plus noise. Floor can be expressed as units, such as microvolts or counts of the least
significant digit. For the 5522A, the floor specification is combined with fixed range
errors in one term to determine total uncertainty.
full scale
The maximum reading of a range of a meter, analog-to-digital converter, or other
measurement device, or the maximum attainable output on a range of a calibrator.
gain error
Same as scale error. Scale or gain error results when the slope of the meter's response
curve is not exactly 1. A meter with only gain error (no offset or linearity error), will read
0V with 0V applied, but something other than 10V with 10V applied.
ground
The voltage reference point in a circuit. Earth ground is a connection through a ground
rod or other conductor to the earth, usually accessible through the ground conductor in an
ac power receptacle.
ground loops
Undesirable currents induced when there is more than one chassis ground potential in a
system of instruments. Ground loops can be minimized by connecting all instruments in a
system to ground to one point.
guard
See "voltage guard" and "current guard."
harmonics
A waveform that is an integral multiple of the fundamental frequency. For example, a
waveform that is twice the frequency of a fundamental is called the second harmonic.
IPTS-68
Refers to the International Provisional Temperature Standard (1968), replaced by the
International Temperature Standard (1990). This specifies the definition of the °C
temperature standard.
ITS-90
Refers to the International Temperature Standard (1990), which replaced the International
Provisional Temperature Standard (1968). This specifies the definition of the °C
temperature standard.
International Systems of Units
Same as "SI System of Units," the accepted system of units. See also "units," "base
units," and "derived units."
legal units
The highest echelon in a system of units, for example the U.S. National Bureau of
Standards volt.
A
Glossary
A-3
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