The Pointek Cls300 Electrode - Siemens Pointek CLS200 Operating Instructions Manual

The Pointek CLS300 electrode

The Pointek CLS300 electrode is the primary sensor of the system. It supplies the
electrical capacitance value.
The Pointek CLS300 patented Active Shield Technology electrically isolates the
measurement section and reduces the effect of any non-measurement capacitance on
the measurement capacitance. (Capacitance changes could result from uncontrolled
variations occurring in the connection cable, process connection, and non-active parts of
the probe.) This gives a better ratio of initial capacitance to total capacitance, resulting in
higher accuracy.
.
R = Ratio between initial
capacitance and total
capacitance
Ca = Initial capacitance (air)
Cm = Capacitance Increase
(product)
C1 = Capacitance connection
point
C2 = Capacitance connection
cable
C3 = Capacitance Process
connection (includes active
part)
The measurement is further protected from interference by a buffer, which applies the
frequency signal from the measurement section to the Active Shield section. This effectively
eliminates any electrical potential difference between the shield and the measurement
section and prevents additional changes in capacitance occurring, especially when
material builds up at the probe entrance to the tank.
Page 34 Pointek CLS200/300 Standard – INSTRUCTION MANUAL
Pointek CLS300 with
Active Shield
R = Ca
Ca + Cm
Measuring
Circuit
Ca
Cm
Conventional Capacitance
Measurement
R = (C1 + C2 + C3) + Ca
(C1 + C2 + C3) + Ca + Cm
Measuring
Circuit
C1
C2
C3
Ca
Cm
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