Function And System Design; Measuring Principle - Endress+Hauser Micropilot FMR51 Technical Information

Measuring principle

6

Function and system design

The Micropilot is a "downward-looking" measuring system, operating based on the time-of-flight
method (ToF). It measures the distance from the reference point (process connection) to the product
surface. Radar impulses are emitted by an antenna, reflected off the product surface and received
again by the radar system.
R
D
L
 1 Setup parameters of the Micropilot
R Reference point of the measurement (lower edge of the flange or threaded connection)
E Empty calibration ( = zero)
F Full calibration (= span)
D Measured distance
L Level (L = E - D)
Input
The reflected radar impulses are received by the antenna and transmitted into the electronics. A
microprocessor evaluates the signal and identifies the level echo caused by the reflection of the radar
impulse at the product surface. The unambiguous signal identification is accomplished by the
PulseMaster® eXact software together with the Multi-echo tracking algorithms, based on many
years of experience with time-of-flight technology.
The distance D to the product surface is proportional to the time of flight t of the impulse:
D = c · t/2,
with c being the speed of light.
Based on the known empty distance E, the level L is calculated:
L = E – D
The reference point R of the measurement is located at the process connection. For details see the
dimensional drawing:
• FMR51: →  64
• FMR52: →  70
The Micropilot is equipped with functions to suppress interference echoes. The user can activate
these functions. Together with the multi-echo tracking algorithms they ensure that interference
echoes (i.e. from edges and weld seams) are not interpreted as level echo.
Micropilot FMR51, FMR52
100%
E
F
0%
Endress+Hauser
A0017871