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Series 220/221 Instruction Manual Appendix B Glossary
Q R S T
Q Flow rate, usually volumetric.
Rangeability Highest measurable flow rate divided by the lowest
measurable flow rate.
Reynolds Number A dimensionless number equal to the density of a fluid
or Re times the velocity of the fluid times the diameter of the
fluid channel, divided by the fluid viscosity (i.e., Re =
ρVD/µ). The Reynolds number is an important num-
ber for vortex flow meters because it is used to deter-
mine the minimum measurable flow rate. It is the ratio
of the inertial forces to the viscous forces in a flowing
fluid.
RTD Resistance temperature detector, a sensor whose
resistance increases as the temperature rises.
scfm Standard cubic feet per minute (flow rate converted
to standard conditions, usually 14.7 psia and 20° C).
Shedder Bar A non-streamlined body placed into a flow stream to
create vortices. Also called a Bluff Body.
Strouhal Number A dimensionless number equal to the frequency
or St of vortices created by a bluff body times the width of
the bluff body divided by the velocity of the flowing
fluid (i.e., St = fd/V). This is an important number for
vortex flow meters because it relates the vortex fre-
quency to the fluid velocity.
Totalizer An electronic counter which records the total accu-
mulated flow over a certain range of time.
Traverse The act of moving a measuring point across the
width of a flow channel.
U V W X Y Z
Uncertainty The closeness of agreement between the result of a
measurement and the true value of the measurement.
V Velocity or voltage.
VAC Volts, alternating current.
VDC Volts, direct current.
VORTEX An eddy of fluid.
IM-22 B-3