Measuring Conditions - Endress+Hauser FOUNDATION Fieldbus Micropilot FMR50 Brief Operating Instructions

Installation
6.2

Measuring conditions

• In case of boiling surfaces, bubbling or tendency for foaming use FMR53 or FMR54.
Depending on its consistence, foam can either absorb microwaves or reflect them off the
foam surface. Measurement is possible under certain conditions. For FMR50, FMR51 and
FMR52, the additional option "Advanced dynamics" is recommended in these cases (feature
540: "Application Package", option EM).
• In case of heavy steam development or condensate, the maximum measuring range of
FMR50, FMR51 and FMR52 may decrease depending on density, temperature and
composition of the steam → use FMR53 or FMR54.
• For the measurement of absorbing gases such as ammonia NH
please use Levelflex or Micropilot FMR54 in a stilling well.
• The measuring range begins, where the beam hits the tank bottom. Particularly with dish
bottoms or conical outlets the level cannot be detected below this point.
• In stilling well applications, the electromagnetic waves do not propagate completely outside
the tube. It must be taken into account that the accuracy may be reduced in the area C. In
order to guarantee the required accuracy in these cases, it is recommended to position the
zero-point at a distance C above the end of the tube (see figure).
• In case of media with a low dielectric constant (ε
visible through the medium at low levels (low height C). Reduced accuracy has to be
expected in this range. If this is not acceptable, we recommend positioning the zero point at
a distance C (see figure) above the tank bottom in these applications.
• 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 chosen any closer than A (see figure) to the tip of the
antenna.
• When using FMR54 with planar antenna, especially for media with low dielectric constants,
the end of the measuring range should not be closer than A: 1 m (3.28 ft) to the flange.
• The smallest possible measuring range B depends on the antenna version (see figure).
• The tank height should be at least H (see table).
1) Affected compounds are e.g. R134a, R227, Dymel 152a.
2) Dielectric constants of important media commonly used in various industries are summarized in the DC manual
(CP01076F) and in the Endress+Hauser "DC Values App" (available for Android and iOS).
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Micropilot FMR50 FOUNDATION Fieldbus
or some fluorocarbons
3
2)
= 1.5 to 4) the tank bottom can be
r
1)
,
Endress+Hauser