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current guard
A generator that drives the inner shield of a triaxial cable with a signal of the same
amplitude and phase as a Calibrator's ac current output signal on the center conductor.
The current guard shields the Calibrator's output signal from a capacitive leakage path to
ground.
DAC (digital-to-analog converter)
A device or circuit that converts a digital waveform to an analog voltage.
dBm
Power level expressed as decibels above or below 1 mW.
derived units
Units in the SI system that are derived from base units. Volts, ohms, and watts are
derived from amperes and other base and derived units.
distortion
Undesired changes in the waveform of a signal. Harmonic distortion disturbs the original
relationship between a frequency and other frequencies naturally related to it.
Intermodulation distortion (imp) introduces new frequencies by the mixing of two or
more original frequencies. Other forms of distortion are phase distortion and transient
distortion.
errors
The different types of errors described in this glossary are: offset error, linearity error,
random error, scale error, systematic errors, and transfer error. Each of these are defined
in this glossary.
flatness
A measure of the variation of the actual output an ac voltage source at different frequency
points when set to the same nominal output level. A flat voltage source exhibits very little
error throughout its frequency range.
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 Calibrator, the floor specification is combined with fixed range
errors in one term.
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.
C
Appendices
Glossary
C-3
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