Micropilot FMR50
38 Endress+Hauser
The beam angle is defined as the angle α where the energy density of the radar waves reaches half
the value of the maximum energy density (3dB width). Microwaves are also emitted outside the
signal beam and can be reflected off interfering installations.
Beam diameter W as a function of beam angle α and distance D.
40 mm / 1 1/2" antenna, α 23 °
W = D × 0.41
80 mm (3 in) antenna, α 10 °
W = D × 0.18
100 mm (4 in) antenna, α 8 °
W = D × 0.14
Process conditions
• Preferably use the FMR53 or FMR54 for boiling surfaces, bubble formation or tendency towards
foam formation. Depending on its consistency, foam can absorb microwaves or reflect them at the
foam surface. Measurements are possible under certain conditions. The additional option
"Advanced dynamics" is recommended for FMR50, FMR51 and FMR52 in these cases (feature 540:
"Application packages", option EM).
• In the event of strong development of steam or condensate, the max. measuring range of
FMR50, FMR51 and FMR52 may decrease depending on the density, temperature and
composition of the steam → use FMR53 or FMR54.
• To measure absorbing gases such as ammonia NH
3
or some fluorocarbons, use the Levelflex or
Micropilot FMR54 in a stilling well.
The connections affected include R134a, R227, Dymel 152a for example.
• The measuring range begins where the beam hits the tank bottom. Levels below this point cannot
be detected, particularly in the case of torispherical heads or conical outlets.
• In stilling well applications, it is important to consider that the electromagnetic waves do not
propagate completely outside the pipe. Reduced accuracy must be expected within range C. If this
is not acceptable, we recommend positioning the zero point at a distance C above the end of the
pipe (see Figure) in these applications.
• In the case of media with a low ε
r
= 1.5 to 4, the tank bottom may be visible through the medium
at low levels (less than level C). Reduced accuracy must be expected in this range. If this is not
acceptable, we recommend positioning the zero point at a distance C above the tank floor (see
Figure) in these applications.
The dielectric constants (ε
r
values) for many key media used in industry are provided in the DC
Manual (CP00019F) and in Endress+Hauser's "DC Values App" (available for Android and iOS).
• In principle it is possible to measure up to the tip of the antenna with FMR51, FMR53 and FMR54.
However, due to considerations regarding corrosion and build-up, the end of the measuring range
should not be any closer than A (see Figure) to the tip of the antenna. In the case of FMR50 and
FMR52, the end of the measuring range should not be any closer than A (see Figure) to the tip of
the antenna, particularly in the event of condensate formation.
• When using FMR54 with a planar antenna, the end of the measuring range should not be closer
than A: 1 m (3.28 ft) to the flange, especially in the case of media with a low dielectric constant.
• The vessel height should be at least H (see Table).
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