Honeywell SLG 700 Option Manual page 151

6.6.2.5 Measurement
Most customers are more interested in the height of the liquid surface or interface relative to some
lower datum point, such as the bottom of the tank, rather than the transmitter's reference plane.
Measurements made relative to this lower, user-defined datum point are referred to as levels to
distinguish them from the distances measured from the transmitter's datum point. In order to convert
distance measurements to level measurements, the following parameters are used to describe the
geometry of the installation:
Sensor Height (A):
Height of the transmitter's Reference Plane above some user-
defined fixed bottom reference plane. This fixed bottom
reference plane should be a location from which accurate
measurements to the reference Plane can be obtained. It may
be the bottom of the vessel but it may also be the ground or
other convenient location and does not necessarily have to be
the plane that represents a level of 0.0.
Level Offset (C):
The distance between the fixed bottom reference plane and
the plane that represents a level of 0.0. This offset may be
positive (upward), negative (downward) or zero if it
coincides with the bottom reference plane. This offset
defines the zero point for the transmitter's level
measurements.
Maximum Product Level (B):
The maximum level reading, in length units, above the Level Offset point that is expected when the
tank is considered full. This parameter is used primarily to allow the level to be reported in units of %
as well as in the specified length units.
Rev.5 FOUNDATION Fieldbus Option User's Manual Page 135