Capacitive
Level Sensors, also referred to as Radio
Frequency (RF) level sensors, are used for
measuring process level at a specific point,
multiple points, or continuously over the
entire vessel height. Capacitance Level
Sensors have the ability to detect and measure
both conductive and non-conductive mediums
such as water and oil, or solids (molasses,
pastes, powder and grains), as well as a
variety of other materials. In addition,
this method is also applicable for detecting
level when there are interfaces between
liquids (such as oil/water). Selecting the
appropriate model and installing it in the
proper location are key factors in successfully
applying Capacitive Level Sensors. That
is why Sitron offers many level measurement
and control solutions. Sitron's Capacitive
Level Sensors are broken into two types:
1. Continuous
Level Measurement (Models SC404, SC120 +
CN200) 2. Point Level Detection (Models
SC400+LV400 and SC700)
Like all
of Sitron's products, the Capacitive Level
Sensors can be made in a wide variety of
process connections. They feature easy installation,
as well as maintenance free reliability
within a compact design.
TECHNOLOGY:
Three elements
are needed to form a capacitor: Two plates
and a dielectric. The capacitance electrode
(the probe) is one plate, the vessel wall
is the other plate, and the medium is the
dielectric. If the vessel is non-metallic,
a conductive ground reference must be inserted
into the vessel or a metallic tubular sheath
can be placed over the probe's capacitance
electrode to form the second plate.
A Capacitive
Level Sensor measures level by applying
a radio frequency (RF) signal between the
capacitance electrode (the probe) and the
electrically conductive vessel wall. The
RF output creates a small amount of electrical
current that flows through the medium (the
dielectric) from the probe to the vessel
wall. When the level increases or decreases
the dielectric constant, or the capacitance
reading, increases or decreases.
In other words,
the level change results in a variation
of the capacitance value around the probe,
depending upon the degree of immersion.
For point level detection, the probe's electronics
detect the change in the RF signal and then
alter the state of the level switch. For
continuous level detection, the probe's
electronics convert the RF signal into a
4-20mA-output signal that is proportional
to the change of the level.
FEATURES:
Wide
range of applications/industries
I.e.
water, oils, corrosives, solids, powders,
grains, etc.
Functions on conductive as well as non-conductive
medias
No moving parts
Rugged construction
Easy economical installation
Accurate and reliable measurement
Unaffected by coating media or aggressive
products
Can operate at high temperatures and
pressure
approved
Required
information to specify the correct type of electronic
module for your application:
1) Provide the generic name of the material,
even if it is a mix of several products.
2) Specify whether liquid, slurry, solid,
interface, granular or powder.
3) Inform viscosity, density and describe
consistency in such terms as “watery,” “oily,” “like
a batter” or “like molasses.” If this information
is not available, a sample for evaluation is required.
4) Give process information describing if
it is nominal, minimum and maximum temperature and
pressure ranges. If turbulence is present, indicate
its degree.
5) Describe tank material and its shape.
6) Describe area classification: non-hazardous,
hazardous or corrosive.
7) Provide a schematic diagram showing desired
probe mounting and location, zero percent and 100
percent of level as well as the presence of an agitator
or other internal obstructions.
approved
