SICK FLOWSIC600, Техническая информация, Страница: 22 / 262

22 FLOWSIC600 · Technical Information · 8010125 V 4.0 · © SICK AG
Product Description
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2.3.1
Determining the gas velocity
Measuring cycle
In the operating status "Measurement", the FLOWSIC600 determines the gas velocity on
each path 10 times per second. One measuring cycle consists of a velocity measurement
per path, the integration of the operating volume, several internal procedures and the
update of the measured value output channels. This cycle takes about 100 ms.
Determining the transit time of the ultrasonic signals
A full analysis of the ultrasonic signals makes it possible to determine the point of time of
signal reception, and thus the delay to the point of time of signal transmission. The signal
propagation times in the flowing gas, t
AB
and t
BA
, are determined on the basis of this
transit time.
Path velocity
The path velocity (v
Path i
) is calculated from the difference between the two transit times:
L
i
is the distance between the two transducer diaphragms.
This distance is calculated by subtracting the length of the transducers used (Reg. #7109
to #7116 "SensorLength i AB") from the distance between the transducer seats in the
meter body (Reg. #7105 to #7108 "Length i").
L
i
= L
Meter body i
- (L
Transducer A i
+ L
Transducer B i
)
Sound transit time in the direction of flow t
AB:
Sound transit time against the direction of flow t
BA
:
Path number 1 ... 4:
v
Path i
: Measuring
values in
registers #7507
to #7510

i: Register #7101 to
#7104
L: Measuring path
length
c: Speed of sound
v
Path
:Path velocity

: Angle between
the longitudinal
axis of the meter
body and the
path
t
AB
=
c + v
Path
· cos

L
t
BA
=
c - v
Path
·
cos

L
L
i
1 1
2
•
cos

i
t
AB i
t
BA i
v
Path i
=
·
( )