Emerson Rosemount 3300 Series Reference Manual page 47

Reference Manual
00809-0100-4811, Rev AB
July 2003
Reference Gauge Height
The Reference Gauge Height is the distance from the Upper Reference Point
to the bottom of the tank. The transmitter measures the distance to the
product surface and subtracts this value from the Reference Gauge Height to
determine the level.
Probe Length
The probe length is the distance between the Upper Reference Point and the
end of the probe. If a weight is used at the end of the probe it shall not be
included.
This parameter is pre-configured at factory. It must be changed if the probe is
shortened.
Probe Type
The transmitter is designed to optimize measurement performance for each
probe type.
This parameter is pre-configured at factory. This value needs to be changed if
the probe type is changed.
Flexible and Rigid probes require different radar electronics and can not be
used with the same transmitter head.
Dielectric Constant of Upper Product
For interface measurements the dielectric constant of the upper product is
essential in order to obtain good accuracy. See section "Interface" on
page 2-9 for further information on dielectric constants.
If the dielectric constant of the lower product is significantly smaller than the
dielectric constant of water, you may need to make special adjustments. See
section "Interface Measurements for Semi-Transparent Bottom Products" on
page 6-5 for further information.
For level measurements the Upper Product Dielectric parameter corresponds
to the actual dielectric constant of the product in the tank. Normally this
parameter does not need to be changed even if the actual dielectric constant
of the product deviates from the Upper Product Dielectric parameter value.
However, for some products measurement performance can be optimized by
setting the proper product dielectric constant.
Dielectric Constant of Vapor
In some applications there is heavy vapor above the product surface having a
significant influence on the level measurement. In such cases the vapor
dielectric can be entered to compensate for this effect.
The default value is equal to 1 which corresponds to the dielectricity of
vacuum. Normally this value does not need to be changed since the effect on
measurement performance is very small for most vapors.
Upper Null Zone
This parameter should only be changed if there are measurement problems in
the upper part of the tank. Such problems may occur if there are disturbing
objects close to the probe. By setting the Upper Null Zone the measuring
range is reduced. See Section 6: Disturbances at the top of the tank for
further information.
Rosemount 3300 Series
4-3