Below we will offer a new improved compensated C4D (Capacitively Coupled Contactless Conductivity Compensated Detection) electronic arrangement that excludes the stray capacitance
leakage effect by introducing the parallel idle channel with inversed AC input signal.
The proposed capacitive probe shown in Fig.2 consists of a three-part coaxial capacitive sensor in which the middle one is acting as the main sensing probe and the other two capacitors considered as the guard rings in order to reduce the stray capacitance
effect and the source of errors in measurements (it must be mentioned that such design is more useful for the case of small capacitance change measurements).
A flooded ground plane does not prevent this because stray capacitance
will still be formed between the electrodes/traces and the ground plane since they are also at different DC potentials.
In the same way C([x.sub.i]) is the global stray capacitance
(pF) calculated using:
Since the stray capacitance
is negligible compared to the term [I.sub.s]/([U.sub.s]j[omega]) predetermined by the amplifier (Hage and Werther, 1997), the measured voltage U * ([C.sub.X]) can be directly connected to [C.sub.x] and finally using an appropriate calibration procedure linked to the corresponding solids concentration to be determined (Figure 3).
With high levels of stray capacitance
, a binary tree switch structure would be required to achieve broad bandwidth.
Twin lead antenna cable minimizes stray capacitance
in the connections to the electrodes.
This may not be enough to protect networks from lead inductance and/or stray capacitance
. Equipment chassis can be tied together with a short and wide ground strap.
During turn-on there is a risk of high inrush current forming due to the charging of the stray capacitance
, however it can be diminished by a ballast resistor in series with the load.
Since capacitance adds in parallel, the total capacitance of a coil is not lower than the sum of the stray capacitance
of the coil and the lumped capacitance added.
Inserting series resistors is a simple edge-speed reduction approach that uses a circuit's stray capacitance
The capacitance of the feedback element should be at least 10 pF to avoid errors due to stray capacitance
and noise gain.