Endress+Hauser Waterpilot FMX21 - Page 38

Commissioning Waterpilot FMX21
38 Endress+Hauser
9.9.2 Overview of level measurement
Measuring task Level
selection
Measured variable
options
Description Measured value display
Calibration is
performed by entering
two pressure-level
value pairs.
"In pressure" Via the "Output unit"
parameter:
%, level, volume or
mass units
• Calibration with
reference pressure (wet
calibration) →  40
• Calibration without
reference pressure (dry
calibration)→  38
The measured value
display and the "Level
before lin" parameter
display the measured
value.
Calibration is
performed by entering
the density and two
height-level value
pairs.
"In height" • Calibration with
reference pressure (wet
calibration) →  40
• Calibration without
reference pressure (dry
calibration)→  40
9.9.3 "In pressure" level selection Calibration without reference pressure (dry
calibration)
Example:
In this example, the volume in a tank should be measured in liters. The maximum volume of
1 000 l (264 gal) corresponds to a pressure of 400 mbar (6 psi).
The minimum volume of 0 liters corresponds to a pressure of 0 mbar since the process
isolating diaphragm of the probe is at the start of the level measuring range.
Prerequisite:
• The measured variable is in direct proportion to the pressure.
• This is a theoretical calibration i.e. the pressure and volume values for the lower and upper
calibration point must be known.
• The values entered for "Empty calib./Full calib.", "Empty pressure/Full pressure" and "Set
LRV/Set URV" must be at least 1% apart. The value will be rejected, and a message
displayed, if the values are too close together. Further limit values are not checked, i.e.
the values entered must be appropriate for the sensor module and the measuring task
for the device to be able to measure correctly.
• Due to the orientation of the device, there may be pressure shifts in the measured
value, i.e. when the vessel is empty or partly filled, the measured value is not zero. For
information on how to perform position adjustment, see →  36.