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flow coefficient Product of the discharge coefficient and
the velocity of approach factor; used in a flow meter
calculation.
flow nozzle Flow meter consisting of a gradual concentric
contraction from a larger diameter to a smaller throat
diameter that is inserted into a pipe to create a
measurable pressure drop proportional to flow rate.
Fourier transform Mathematical function that allows a
complex signal to be decomposed into its frequency
components.
frequency bandwidth The range of frequencies in
which the magnitude ratio remains within 3 db of
unity.
frequency response The magnitude ratio and phase
shift of a system as a function of applied input
frequency.
full-scale output (FSO) The arithmetic difference
between the end points (range) of a calibration
expressed in units of the output variable.
fundamental frequency Smallest frequency component
of a signal.
gain Result of amplification or some multiplier of a
signal magnitude; also used to refer to a constant
multiplier for a transfer function block.
galvanometer Instrument that is sensitive to current
flow through torque on a current loop; typically used to
detect a state of zero current flow.
gauge blocks Working length standard for machining
and calibration.
gauge factor Property of a strain gauge that relates
changes in electrical resistance to strain.
gauge length Effective length over which a strain gauge
averages strain during a measurement.
ground Signal return path to earth.
ground loop A signal circuit formed by grounding a
signal at more than one point with the ground points
having different voltage potentials.
Hall effect Voltage induced across a current-carrying
conductor situated within a magnetic field. The
magnetic field exerts a transverse force pushing the
charged electrons to one side of the conductor.
handshake An interface procedure to control data flow
between different devices that includes start and stop
(hello and goodbye) signals.
high-pass filter A device that allows signal frequencies
above the cut-off frequency to pass unaltered, while
lower frequencies are attenuated.
Hooke’s law The fundamental linear relation between
stress and strain. The proportionality constant is the
modulus of elasticity.
hysteresis A difference in the indicated value for any
particular input value when approached going upscale
as opposed to going downscale.
immersion errors Temperature measurement errors due
to the measuring environment leading to differences
between sensor temperature and the temperature being
measured.
impedance matching Process of setting either the input
impedance or the output impedance in a way to keep
signal loading errors to an acceptable level.
independent variable A variable whose value is
changed directly to cause a change in the value of a
dependent variable.
indicated value The value displayed or indicated by the
measurement system.
input value Process information sensed by the
measurement system.
insertion error Any error brought on by the interaction
between a sensor and the immediate environment in
which it is installed.
in situ In measurements, this means installed in the
system as intended for use.
interference Extraneous effect that imposes a
deterministic trend on the measured signal.
interferometer Device for measuring length that uses
interference patterns of light sources; provides very
high resolution.
interrupt A signal to initiate a different procedure;
analogous to raising one’s hand.
junction For thermocouples, an electrical connection
between two dissimilar materials.
laminar flow element Device that measures flow rate
by the linear pressure drop versus flow rate
relationship occurring when fluid travels through a
tube or cluster of tubes under laminar flow conditions.
least squares regression Analysis tool used to generate a
curve fit equation that minimizes the sum of the squares
of the deviations between the predicted values of the
curve fit and the data set on which the curve fit is based.
line standard Standard for length made by scribing two
marks on a dimensionally stable material.
linearity The closeness of a calibration curve to a
straight line.
load cell Sensor for measuring force or load.
loading error Error due to energy being extracted
from the variable being measured by the very act
of measurement so as to change the value
measured.
low-pass filter A device that allows signal frequencies
below the cut-off frequency to pass unaltered, while
higher frequencies are attenuated.
linear variable differential transformer (LVDT) A
sensor/transducer that provides a voltage output as a
function of core displacement.
Mach number Ratio of the local speed to the speed of
sound in the medium.
magnitude ratio The ratio of the values of output
amplitude to the input amplitude of a dynamic signal.
mass flow rate Mass flow per unit time.
measurand Measured variable.
580 Glossary
11:19:49 Page 580
flow coefficient Product of the discharge coefficient and
the velocity of approach factor; used in a flow meter
calculation.
flow nozzle Flow meter consisting of a gradual concentric
contraction from a larger diameter to a smaller throat
diameter that is inserted into a pipe to create a
measurable pressure drop proportional to flow rate.
Fourier transform Mathematical function that allows a
complex signal to be decomposed into its frequency
components.
frequency bandwidth The range of frequencies in
which the magnitude ratio remains within 3 db of
unity.
frequency response The magnitude ratio and phase
shift of a system as a function of applied input
frequency.
full-scale output (FSO) The arithmetic difference
between the end points (range) of a calibration
expressed in units of the output variable.
fundamental frequency Smallest frequency component
of a signal.
gain Result of amplification or some multiplier of a
signal magnitude; also used to refer to a constant
multiplier for a transfer function block.
galvanometer Instrument that is sensitive to current
flow through torque on a current loop; typically used to
detect a state of zero current flow.
gauge blocks Working length standard for machining
and calibration.
gauge factor Property of a strain gauge that relates
changes in electrical resistance to strain.
gauge length Effective length over which a strain gauge
averages strain during a measurement.
ground Signal return path to earth.
ground loop A signal circuit formed by grounding a
signal at more than one point with the ground points
having different voltage potentials.
Hall effect Voltage induced across a current-carrying
conductor situated within a magnetic field. The
magnetic field exerts a transverse force pushing the
charged electrons to one side of the conductor.
handshake An interface procedure to control data flow
between different devices that includes start and stop
(hello and goodbye) signals.
high-pass filter A device that allows signal frequencies
above the cut-off frequency to pass unaltered, while
lower frequencies are attenuated.
Hooke’s law The fundamental linear relation between
stress and strain. The proportionality constant is the
modulus of elasticity.
hysteresis A difference in the indicated value for any
particular input value when approached going upscale
as opposed to going downscale.
immersion errors Temperature measurement errors due
to the measuring environment leading to differences
between sensor temperature and the temperature being
measured.
impedance matching Process of setting either the input
impedance or the output impedance in a way to keep
signal loading errors to an acceptable level.
independent variable A variable whose value is
changed directly to cause a change in the value of a
dependent variable.
indicated value The value displayed or indicated by the
measurement system.
input value Process information sensed by the
measurement system.
insertion error Any error brought on by the interaction
between a sensor and the immediate environment in
which it is installed.
in situ In measurements, this means installed in the
system as intended for use.
interference Extraneous effect that imposes a
deterministic trend on the measured signal.
interferometer Device for measuring length that uses
interference patterns of light sources; provides very
high resolution.
interrupt A signal to initiate a different procedure;
analogous to raising one’s hand.
junction For thermocouples, an electrical connection
between two dissimilar materials.
laminar flow element Device that measures flow rate
by the linear pressure drop versus flow rate
relationship occurring when fluid travels through a
tube or cluster of tubes under laminar flow conditions.
least squares regression Analysis tool used to generate a
curve fit equation that minimizes the sum of the squares
of the deviations between the predicted values of the
curve fit and the data set on which the curve fit is based.
line standard Standard for length made by scribing two
marks on a dimensionally stable material.
linearity The closeness of a calibration curve to a
straight line.
load cell Sensor for measuring force or load.
loading error Error due to energy being extracted
from the variable being measured by the very act
of measurement so as to change the value
measured.
low-pass filter A device that allows signal frequencies
below the cut-off frequency to pass unaltered, while
higher frequencies are attenuated.
linear variable differential transformer (LVDT) A
sensor/transducer that provides a voltage output as a
function of core displacement.
Mach number Ratio of the local speed to the speed of
sound in the medium.
magnitude ratio The ratio of the values of output
amplitude to the input amplitude of a dynamic signal.
mass flow rate Mass flow per unit time.
measurand Measured variable.
580 Glossary