Function And System Design; Measuring Principle - Endress+Hauser Prosonic T FMU30 Technical Information

Prosonic T FMU30

Measuring principle

Endress+Hauser
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Function and system design

BD Blocking distance
E Empty distance
L Level
Sensor BD
1½" 0.25 m (0.8 ft)
2" 0.35 m (1.1 ft)
Time-of-flight method
The sensor of the instrument transmits ultrasonic pulses in the direction of the product surface. There, they are
reflected back and received by the sensor. The instrument measures the time t between pulse transmission and
reception. The instrument uses the time t (and the velocity of sound c) to calculate the distance D between the
sensor membrane and the product surface:
D = c  t/2
As the device knows the empty distance E from a user entry, it can calculate the level as follows:
L = E - D
An integrated temperature sensor (NTC) compensates for changes in the velocity of sound caused by
temperature changes.
Interference echo suppression
The interference echo suppression feature on the instrument ensures that interference echos (e.g. from edges,
welded joints and installations) are not interpreted as a level echo.
Calibration
Enter the empty distance E and the span F to calibrate the device.
Blocking distance
Span F may not extend into the blocking distance BD. Level echos within the blocking distance cannot be
evaluated due to the transient characteristics of the sensor.
BD
D
E
F
L
D Distance from sensor membrane - product surface
F Span (full distance)
Max. range fluids
5 m (16 ft)
8 m (26 ft)
20 mA
100%
4 mA
0%
L00-FMU30-15-00-00-xx-001
Max. range bulk materials
2 m (6.6 ft)
3.5 m (11 ft)
3