SICK FLOWSIC100 Flare-XT User Manual

System description
FLOWSIC100 Flare-XT · Operating Instructions · 8023761/V 1-0/2020-10 · © SICK Engineering GmbH 17
3.2
Functional principle
The FLOWSIC100 Flare-XT gas flow rate measuring devices operate according to the
principle of ultrasonic transit time difference measurement. Sender/receiver units are
mounted on both sides of a pipeline at a certain angle of inclination to the gas flow (Fig. 1).
These sender/receiver units contain piezoelectric ultrasonic transducers that function
alternately as senders and receivers. The sound pulses are emitted at an angle  to the
flow direction of the gas. Depending on angle α and gas flow rate v, the transit time of the
respective sound direction varies as a result of certain ”acceleration and braking effects”.
The higher the gas velocity and the smaller the angle to the flow direction, the more the
transit times of the sound pulses differ.
Gas flow rate v is calculated from the difference between both transit times, independent of
the sound velocity value. With this measuring method, changes of the sound velocity due to
pressure or temperature variations therefore have no influence on the gas velocity
determined.
Fig. 1 Functional principle FLOWSIC100 Flare-XT
Linearization
Further process values are required to calculate mass flow, molecular weight, gas density
and Reynolds number. Especially pressure, temperature and viscosity have a significant
influence. The best accuracy is achieved when externally installed pressure and tempera-
ture sensors can be connected to the measuring system. The viscosity can be configured
as a medium constant value.
POWER
Meas
Sender/receiver
unit, slave
(probe B)
v = velocity of gas in m/s
L = measuring path in m
 = angle of inclination in °
t
AB
= sound transit time
in flow direction
t
BA
= sound transit time
against flow direction
Sender/
receiver unit,
master
(probe A)
t
BA
v

t
AB
L
Higher level
control system (Interface Unit)
NOTICE:
The correct evaluation of the Reynolds number is decisive for the determination
of the correct calibration function. The Reynolds number must be determined
with an accuracy of 20% in order to achieve the device accuracy offered by
SICK.
Re
v D  

-------------------
=
v = Speed of sensor
D = Inner pipe diameter
ρ = Density of medium
η = Viscosity of medium

SICK FLOWSIC100 Flare-XT Specifications

General

Brand	SICK
Model	FLOWSIC100 Flare-XT
Category	Measuring Instruments
Language	English