Siemens Sitrans LR400 Instruction Manual page 41

4.2.2.2 Surface (F = wavy)
Surface structure of the material. Not displayed if a user vessel is selected in
Parameter 4.2.2.1.
Value
This parameter is not displayed when a user vessel is selected in Parameter 4.2.2.1.
When used with poorly reflecting measuring media, you may be able to improve
measuring results by setting a different surface structure here. If your measuring medium
forms waves more than 1 cm in height, you should select the wavy setting. The turbulent
setting is recommended for waves greater than 10 cm.
4.2.2.3 Dead band (F = 0.35 m)
Defines the distance from below the flange to be ignored by the transmitter/receiver
Value
Specification of a dead band in the units system selected according to Parameter 4. 1 .5
defines a minimum distance from the flange which the measuring medium must have for
the device to accept the measured values as valid. This suppresses reflective
interference generated by the nozzle, close obstacles, or the antenna.
For solids applications, a dead band setting of 1 m minimum is recommended.
The dead band must exceed the antenna's length.
Note:
4.2.2.4 Correction Factor (F = 1.0)
Correction factor for physical measuring influences. Generally only applies to liquid
applications using a stilling well.
Value
The propagation time of the microwaves between the antenna and the measuring
medium changes slightly depending on the pressure inside the vessel. If this pressure is
constant, however, it can be included in the evaluation according to the equation:
K = correction factor, p = pressure inside the vessel in bar, Tgas = gas temperature in °C,
ε = dielectric of the overlying gas, e.g. ερ
r, Gas
Enter the correction factor
7ML19985FH06 SITRANS LR400 (7ML5421) – INSTRUCTION MANUAL
Smooth
Wavy
Turbulent
numerical value, Minimum value = Length of the antenna
numerical value
------------------------------------------------------------------------ -
K =
( ε
1 +
,
r Gas
K
as a dimensionless value.
1
273 p ⋅
) ⋅
------------------------- -
– 1
T + 273
Gas
= 1.00059
, air
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