Prosonic S FDU91/92/93/95/96
E Hauser
3
Function and system design
Measuring principle
L00-FMU90xxx-15-00-08-xx-009
BD:
blocking distance;
D:
distance from sensor membrane to fluid surface;
E:
empty ditance
F:
span (full distance);
L:
level;
V:
volume (or mass);
Q:
flow
The sensor transmits ultrasonic pulses in the direction of the product surface. There, they are reflected back
and received by the sensor. The transmitter Prosonic S measures the time t between pulse transmission and
reception. From t (and the velocity of sound c) it calculates the distance D from the sensor membrane to the
product surface:
D = c · t/2
From D results the desired measuring value:
• level L
• volume V
• flow Q across measuring weirs or open channels
Time-of-flight correction
In order to compensate for temperature dependent time-of-flight changes, a temperature sensor is integrated
in every sensor.
Blocking distance
The level L may not extend into the blocking distance BD. Level echoes from the blocking distance can not be
evaluated due to the transient characteristics of the sensor and thus a reliable measurement is not possible.
The blocking distance BD is dependent on the type of sensor:
Transmitter
The sensors can be connected to the transmitter FMU90. The transmitter recognizes the type of sensor
automatically.
FDU9x
Prosonic S
FMU90
Prosonic S
FMU90
FDU9x
D
Q
100%
0%
D
L
F
E
BD
V
Type of sensor
Blocking distance (BD)
FDU91
0,3 m
FDU92
0,5 m
FDU93
0,6 m
FDU95 - *1*** (low temperature version)
0,7 m
FDU95 - *2*** (high temperature version)
0,9 m
FDU96
1,6 m
