Micropilot FMR51, FMR52
Endress+Hauser 35
error for a few typical gases/vapors (with regard to distance; a positive value means that too large a
distance is being measured):
Gas layer Temperature Pressure
°C °F 1 bar (14,5 psi) 10 bar (145 psi) 50 bar (725 psi) 100 bar (1450 psi) 160 bar (2320 psi)
Air/
Nitrogen
20 68 0.00 % 0.22 % 1.2 % 2.4 % 3.89 %
200 392 –0.01 % 0.13 % 0.74 % 1.5 % 2.42 %
400 752 –0.02 % 0.08 % 0.52 % 1.1 % 1.70 %
Hydrogen 20 68 –0.01 % 0.10 % 0.61 % 1.2 % 2.00 %
200 392 –0.02 % 0.05 % 0.37 % 0.76 % 1.23 %
400 752 –0.02 % 0.03 % 0.25 % 0.53 % 0.86 %
Water
(saturated
steam)
100 212 0.02 % - - - -
180 356 - 2.1 % - - -
263 505,4 - - 8.6 % - -
310 590 - - - 22 % -
364 687 - - - - 41.8 %
When the pressure is known and constant, this measured error can, for example, be
compensated by means of a linearization.
Gas phase compensation
with external pressure
sensor (PROFIBUS PA,
FOUNDATION Fieldbus)
PROFIBUS devices can receive the signal of an external pressure sensor through the bus and use it to
perform a pressure dependent time-of-flight correction. In the case of saturated steam in the
temperature range from 100 to 350 °C (212 to 662 °f), for example, the measuring error of the
distance measurement can be reduced by this method from up to 29 % (without compensation) to
less than 3 % (with compensation).
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