TÜV-A 03 ATEX 0019X
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cbr2052a0600p_01
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36/5
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We are sure that you will be satisfied throughout its use
1. INTRODUCTION
NIVOCAP CT-200 is a two-wire capacitance level transmitter for measuring level and volume (weight) of conductive or not-conductive liquids or free flowing
solids.
A
PPLICATION
The active probe of the unit and the conductive wall of the vessel (or a grounded reference probe if the wall is not conductive) make up the plates of a capacitor.
Insulator of the probe, surrounding air or the material in the tank provide dielectric material.
If the tank is empty the basic capacitance is C
0
while the dielectric coefficient “
ε
r
” of the air is 1. If the air will be replaced by material with higher dielectric
constant than that of the air, the capacitance will be changed, i.e. capacitance will increase with rising material. This change of the sensed capacitance
converted to output signal will be proportional to the level change.
The same time the condition of level gauging is direct proportionality between the level
change and the change of the capacitance.
The value of capacitance also depends on the distance between the plates, the condition above will be met if the active probe is parallel to he tank wall or with
the reference probe. Thus reference probe should be used in a tank with unusual shape or cylindric tank in a horizontal position even if the wall is conductive,
provided the medium is not conductive.
Due to the level measurement on the capacitance principle it is essential to measure and store capacitance at two different levels in the tank (teaching), when
the unit is “learning “ surrounding conditions of the actual application (e.g. C
0
is different on the workshop bench and on site in the tank etc.).
Improper selection of the probe and very low dielectric constant may prevent the measurement.
For conductive materials (e.g.. water, acid,, bases, solutions with water, etc.) insulated active probes should be used., while value of the dielectric constant is
indifferent. Both insulated and uninsulated probes can be used for non conductive materials but dielectric constant must be over 1.5 (
ε
r
> 1.5).
V
OLUME AND WEIGHT MEASUREMENT
This measurement is supported by the volumetric calculation feature and arithmetical formula for the most commonly used tank shapes in the software. Thus
measuring level, volume or weight of the medium in the tank can be transmitted and displayed.
L
INEARISATION
If there is no direct proportionality between the change of capacitance and change of level the 32-point linearisation feature should be applied. Linearisation is
the method of assigning calibrated volume values to level values measured by the unit.
