Micropilot FMR67
8
V. 1, Rev. 3, 11-04-2017
Hauser
Function and system design
Measuring principle
The Micropilot is a "downward-looking" measuring system, operating based on the frequency
modulated continuous wave method (FMCW). The antenna emits an electromagnetic wave at a
continuously varying frequency. This wave is reflected by the product and received again by the
antenna.
D
R
A0032017
1
FMCW principle: transmission and reflection of the continuous wave
R
Reference point of measurement
D
Distance between reference point and product surface
The frequency of this wave is modulated in the form of a sawtooth signal between two limit
frequencies
f
1
and
f
2
:
f
t
1
2
f
2
f
1
Δt
Δf
A0023771
2
FMCW principle: result of frequency modulation
1
Transmitted signal
2
Received signal
This results in the following difference frequency at any time between the transmitted signal and the
received signal:
Δ
f
=
k
Δ
t
where Δ
t
is the run time and
k
is the specified increase in frequency modulation.
Δ
t
is given by the distance
D
between the reference point
R
and the product surface:
D
= (
c
Δ
t
) / 2
where
c
is the speed of propagation of the wave.
In summary,
D
can be calculated from the measured difference frequency Δ
f
.
D
is then used to
determine the content of the tank or silo.
