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that accurately measures the volume of fluid passing
per unit time.
Prony brake A historically significant dynamometer
design that uses mechanical friction to dissipate and
measure power.
proving ring An elastic load cell, which may be used as
a local calibration standard.
pyranometer Optical instrument used to measure
irradiation on a plane.
quantization Process of converting an analog value into
a digital number.
quantization error An error brought on by the
resolution of an A/D converter.
radiation error Temperature measurement insertion
error caused by a radiative heat exchange between a
temperature sensor and portions of its immediate
environment not at the same temperature as the
variable being measured.
radiation shield A device which reduces radiative heat
transfer to a temperature sensor, to reduce insertion
errors associated with radiation.
radiometer Device for measuring radiative source
temperature using a thermopile detector.
random error The portion of error that varies randomly
on repeated measurements of the same variable.
random standard uncertainty The random uncertainty
estimated at the one standard deviation level or at the
68% probability level for a normal distribution.
random uncertainty Uncertainty assigned to a random
error; contribution to combined uncertainty due to
random errors.
random test Measurement strategy that sets a
random order to the changes in the independent
variable.
randomization methods Test methods used to break up
the interference effects from extraneous variables by
strategies that randomize the effects of those variables
on the data set.
range The lower to upper limits of an instrument or test.
recovery errors Temperature measurement error in a
high speed flowing gas stream related to the
conversion of kinetic energy into a temperature rise at
the sensor.
reference junction In reference to a thermocouple, it is
the junction at which the temperature is known.
repeatability Instrument specification estimating the
expected random uncertainty based on multiple tests
within a given lab on a single unit.
repetition Repeating measurements during the same test.
replication Duplicating a test under similar operating
conditions using similar instruments.
reproducibility Random uncertainty estimate based on
multiple tests performed in different labs on a single unit.
resistivity Material property describing the basic
electrical resistance of a material.
resolution The smallest detectable change in a
measured value as indicated by the measuring system.
resonance frequency The frequency at which the
magnitude ratio reaches a maximum value greater than
unity.
result The final value determined from a set or sets of
measurements.
resultant A variable calculated from the values of other
variables.
ringing frequency The frequency of the free
oscillations of a damped system; a function of the
natural frequency and damping ratio.
rise time The time required for a first-order system to
respond to 90% of a step change in input signal.
rms value Root-mean-square value.
roll-off slope Decay rate of a filter stopband.
RTD Resistance temperature detector; senses
temperature through changes in electrical resistance of
a conductor.
root-sum-square value (RSS) The value obtained by
taking the square root of the sum of a series of squared
values.
rotating cusp meter A type of positive displacement
flow meter that measures volume flow rate by the rate
at which fluid is displaced within alternating rotating
cusps.
sample A data point or single value of a population.
sample rate The rate or frequency at which data points
are acquired; reciprocal of sample time increment.
sample statistics Statistics of a variable determined
from a set of data points whose set size is less than the
population of that variable.
sample time increment The time interval between two
successive data measurements. Reciprocal of sample
rate.
saturation error Error due to an input value exceeding
the device maximum.
second-order system A dynamic system model whose
behavior includes inertia.
Seebeck effect Source of open circuit electromotive
force in thermocouple circuits.
seismic transducer Instrument for measuring
displacement in time, velocity, or acceleration; based
on a spring-mass-damper system.
sensitivity The rate of change of a variable (y) relative
to a change in some other variable (x), for example,
dy=dx.
sensitivity index The sensitivity between two variables
evaluated at some operating point and used to weight
individual uncertainties in uncertainty propagation.
serial communication Technique that transmits
information 1 bit at a time.
sensor The portion of the measurement system that
senses or responds directly to the process variable
being measured.
582 Glossary
11:19:49 Page 582
that accurately measures the volume of fluid passing
per unit time.
Prony brake A historically significant dynamometer
design that uses mechanical friction to dissipate and
measure power.
proving ring An elastic load cell, which may be used as
a local calibration standard.
pyranometer Optical instrument used to measure
irradiation on a plane.
quantization Process of converting an analog value into
a digital number.
quantization error An error brought on by the
resolution of an A/D converter.
radiation error Temperature measurement insertion
error caused by a radiative heat exchange between a
temperature sensor and portions of its immediate
environment not at the same temperature as the
variable being measured.
radiation shield A device which reduces radiative heat
transfer to a temperature sensor, to reduce insertion
errors associated with radiation.
radiometer Device for measuring radiative source
temperature using a thermopile detector.
random error The portion of error that varies randomly
on repeated measurements of the same variable.
random standard uncertainty The random uncertainty
estimated at the one standard deviation level or at the
68% probability level for a normal distribution.
random uncertainty Uncertainty assigned to a random
error; contribution to combined uncertainty due to
random errors.
random test Measurement strategy that sets a
random order to the changes in the independent
variable.
randomization methods Test methods used to break up
the interference effects from extraneous variables by
strategies that randomize the effects of those variables
on the data set.
range The lower to upper limits of an instrument or test.
recovery errors Temperature measurement error in a
high speed flowing gas stream related to the
conversion of kinetic energy into a temperature rise at
the sensor.
reference junction In reference to a thermocouple, it is
the junction at which the temperature is known.
repeatability Instrument specification estimating the
expected random uncertainty based on multiple tests
within a given lab on a single unit.
repetition Repeating measurements during the same test.
replication Duplicating a test under similar operating
conditions using similar instruments.
reproducibility Random uncertainty estimate based on
multiple tests performed in different labs on a single unit.
resistivity Material property describing the basic
electrical resistance of a material.
resolution The smallest detectable change in a
measured value as indicated by the measuring system.
resonance frequency The frequency at which the
magnitude ratio reaches a maximum value greater than
unity.
result The final value determined from a set or sets of
measurements.
resultant A variable calculated from the values of other
variables.
ringing frequency The frequency of the free
oscillations of a damped system; a function of the
natural frequency and damping ratio.
rise time The time required for a first-order system to
respond to 90% of a step change in input signal.
rms value Root-mean-square value.
roll-off slope Decay rate of a filter stopband.
RTD Resistance temperature detector; senses
temperature through changes in electrical resistance of
a conductor.
root-sum-square value (RSS) The value obtained by
taking the square root of the sum of a series of squared
values.
rotating cusp meter A type of positive displacement
flow meter that measures volume flow rate by the rate
at which fluid is displaced within alternating rotating
cusps.
sample A data point or single value of a population.
sample rate The rate or frequency at which data points
are acquired; reciprocal of sample time increment.
sample statistics Statistics of a variable determined
from a set of data points whose set size is less than the
population of that variable.
sample time increment The time interval between two
successive data measurements. Reciprocal of sample
rate.
saturation error Error due to an input value exceeding
the device maximum.
second-order system A dynamic system model whose
behavior includes inertia.
Seebeck effect Source of open circuit electromotive
force in thermocouple circuits.
seismic transducer Instrument for measuring
displacement in time, velocity, or acceleration; based
on a spring-mass-damper system.
sensitivity The rate of change of a variable (y) relative
to a change in some other variable (x), for example,
dy=dx.
sensitivity index The sensitivity between two variables
evaluated at some operating point and used to weight
individual uncertainties in uncertainty propagation.
serial communication Technique that transmits
information 1 bit at a time.
sensor The portion of the measurement system that
senses or responds directly to the process variable
being measured.
582 Glossary