Function And System Design; Measuring Principle; Blocking Distance; Time-Of-Flight Correction - Endress+Hauser Prosonic S FMU90 Technical Information

Prosonic S FMU90

Measuring principle

Blocking distance

Time-of-flight correction

Interference echo suppression

Pump control

Endress + Hauser

Function and system design

FDU9x
BD
D
E F
V
L
BD: blocking distance; D: distance from sensor membrane to fluid surface; E: empty distance 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
The span F may not extend into the blocking distance BD. Level echos from the blocking distance can not be
evaluated due to the transient characteristics of the sensor. The blocking distances of the individual sensors are
given in the following documents:
• TI 396F for the sensors FDU 91/91F/92/93/95/96
• TI 189F for the sensors FDU 80/80F/81/81F/82/83/84/85/86
In order to compensate for temperature dependent time-of-flight changes, a temperature sensor is integrated
in the ultrasonic sensors.
Optionally, the Prosonic S FMU90 has an input for an external temperature sensor
(FMU90-********B***). The following sensor can be connected:
• Pt100
• FMT131 from Endress+Hauser
The external sensor mus be used for the heated version of the ulstrasonic sensor FDU91.
The interference echo suppression feature of the Prosonic S ensures that interference echos (e.g. from edges,
welded joints and installations) are not interpreted as a level echo.
individaully configurable for each pump:
• pump switching delay, e.g. to prevent overlaod of the power supply system
• backlash time and backlash interval, e.g. for complete draining of shafts or channels
• crust reduction at pump shaft walls by fine adjustment of the switch point
100%
Prosonic S
FDU9x
FMU90
0%
Prosonic S
FMU90
D
Q
L00-FMU90xxx-15-00-08-xx-009
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