High Frequency Oscillator; Counts; Detection Range; Cls200 Electrode - Siemens Pointek CLS200 Operating Instructions Manual

Technical reference
A.2 High frequency oscillator
A.2

High frequency oscillator

The Pointek CLS200/300 probe is equipped with a high frequency oscillator which responds
to the capacitance. The inverse of frequency is proportional to the capacitance. A small
change in capacitance results in a large change in frequency which is easy to detect, resulting
in high resolution and accuracy.
A.3

Counts

Frequency is always represented in "counts", a dimensionless, uncalibrated value generated
from the inverse of frequency. The measured value is displayed in counts. (If you are using
PROFIBUS PA, you can set the measuring limits, in counts.)
A.4

Detection range

The functional detection range depends on the relative dielectric constant of the material
monitored. The detection range will be shorter when the material has a lower relative
dielectric constant, and longer when it has a higher relative dielectric constant.
See Technical data (Page 80), for performance information; also check the product
nameplate on the enclosure, for details of your particular instrument.
A.5

CLS200 electrode

The Pointek CLS200 electrode is the primary sensor of the system. It supplies the electrical
capacitance value. The reference is the environment at the time of setup.
The design of the Pointek CLS200 probe makes it very sensitive to changes in capacitance in
the immediate vicinity of the electrode tip.
R = (Ca1 + Ca2)/(Ca1 + Ca2 + Cm1 + Cm2)
R = Ratio between initial capacitance and total capacitance
Ca
1
Ca
2
installation
Cm
1
product replacing air
Cm
2
installation caused by product replacing air.
The initial capacitance of the CLS200 itself makes it possible to operate the CLS200 in a
plastic tank where the Ca
metal tank will reduce the effects of external influences on the sensor.
The sensor can be set to detect either the change in capacitance as the product level
approaches the electrode tip, or the change when the probe becomes covered.
88
= Initial capacitance of the CLS200
= Initial capacitance (air) between the probe and the
= Capacitance increase of the CLS200 caused by
= Capacitance increase between the probe and the
and Cm
2
terms would disappear. However, a properly grounded
2
Operating Instructions, 05/2021, A5E47904060-AA
① Measuring circuit
Pointek CLS200/CLS300 digital