Endress+Hauser FMU 40 - Function and System Design

Prosonic M
Endress+Hauser
Function and system design
Time-of-Flight method
The Prosonic M sensor transmits ultrasonic pulses in the direction of the product
surface. The ultrasonic pulse is reflected back and received by the sensor. The
Prosonic M electronics measures the time t between pulse transmission and recep-
tion. Using the time t (and the velocity of sound c), the system calculates the distance
D between the sensor membrane and the product surface
D = c x t/2
As the device knows the empty distance E from the user entry, it can calculate the
level as follows:
L = E - D
An integrated temperature sensor compensates for changes in the velocity of sound
caused by temperature changes.
Interference echo suppression
The interference echo suppression feature ensures that interference echos (such as
welded joints, internal ladder steps, edges and installations) are not interpreted as a
level echo.
Calibration
Enter the empty distance E and the span F to calibrate the system.
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.
Measuring principle
2
Equipment architecture
4 to 20 mA ouput with HART
®
protocol
The Prosonic M can be operated on-site using either the display module VU 331 or
the supplied ToF Tool program. The system can also be operated remotely using the
HART
®
handheld terminal DXR 275 or using the ToF Tool.
NOTE: If a HART
®
communication resistor is not built into the power supply device, a
250Ω communication resistor in the 2-wire line must be inserted.
D
L
F
E
BD
9.84" (250 mm)
15.7" (400 mm)
23.6" (600 mm)
16 ft (5 m)
26 ft (8 m)
50 ft (15 m)
6.5 ft (2 m)
11.5 ft (3.5 m)
23 ft (7 m)
Sensor
BD
20 mA
100%
4 mA
0%
Max. range
in liquids
Max. range
in solids
FMU 40
FMU 41
FMU 43
BD: Blocking Distance
E: Empty calibration
F: Full calibration (span)
D: Distance from sensor
membrane to product level
L: Level
PLC
Commubox
FXA 191
- ToF Tool
HART handheld
DXR 275
FXA 191
or
DXR 275
Transmitter power
supply unit
RMA 422
or RN 221 N
(communication resistor
included)
Operating and
display module
VU 331
Service adapter
FXA 193
- COMMUWIN II
- ToF Tool