KROHNE UFM 600T EN - Manual (Page 9)

B.1 Measuring Principle
Fig. B.1 : Measuring principle
A sound wave that is sent in the direction of the flow through
a medium will travel faster than one that is sent in the oppo-
site direction.
This principle is used in the ultrasonic transit time flowmeter.
Two ultrasound transmitters/receivers are fitted on opposite
sides of the pipe section as shown in Fig. B.1.
Initially transducer A transmits an ultrasonic sound signal that
will be received by transducer B. The time lapse t
AB
between
transmission and reception is measured.
Then the functions of both probes are reversed and the tran-
sit time t
BA
in the opposite direction is measured.
From t
AB
and t
BA
the actual flow can be calculated taking into
account the following factors:
- pipe diameter
- wall thickness
- lining thickness, if applicable
- sonic velocity in the liquid
- sonic velocity in the pipe material
- sonic velocity in the pipe lining material, if applicable
Measurements are taken continuously.
NOTE: Each transducer transmits and receives ultrasound signals.
8
ALTOSONIC
System Description
UFM 600 T