Function
Measuring Principle
The operating principle is based on the
Karman vortex street. When a fluid flows
past a bluff body, vortices are alter-
nately formed on the sides of that body
and are then detached or shed by the
flow. The frequency of vortex shedding
is proportional to the mean flow velocity
and, therefore, to the volumetric flow
(with Re > 4000).
Alternating pressure changes caused
by the vortices are transmitted via
lateral port holes in the bluff body.
The DSC sensor is located within the
bluff body and is well protected from
water hammer and temperature or
pressure shocks.
The capacitive DSC sensor detects the
pressure pulses and converts them into
electrical signals.
Vortex frequency =
St
• v
d
St= Strouhal number
v = velocity of medium
d = width of bluff body
The sensor preamplifier processes the
sinusoidal sensor signal into a flow-
proportional pulse frequency.
This is then converted by the transmitter
(or flow computer) into a standard
output signal.
The same sensor and electronics are
used for all nominal diameters, fluids,
and process temperatures. The sensor
signal is galvanically isolated in the
preamplifier from the output signal.
DSC Sensor
Vibration Compensation
With Prowirl’s DSC sensor, the general
sensitivity of vortex meters to pipeline
vibration has been eliminated. Using
primary, built-in vibration compensation,
pipeline vibration with amplitudes of up
to 1g and frequencies to 500 Hz will not
affect the measurement, regardless of
the axis of acceleration. The compensa-
tion is permanent, and no adjustments
are neccessary.
ti031y04
Vortex measuring
principle
sensor connector
to electronics
sensor seal
meter body
sensor:
wetted part
bluff body
pipe stand
ti031y05
DSC sensor (standard version).
The Prowirl High Pressure version is equipped with
a special titanium DSC sensor with a second contain-
ment.
4
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