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Operating principles
Because of the nonlinear properties of piezoelectric ceramics, obtained image
contains distortions. Because of nonlinear properties of piezoelectric ceramics, it is im­
portant to understand features of the dependence between the control electric field and
the deformation of the piezo ceramic sample, namely, non-linearity and ambiguity of
this relationship. Usually, the nonlinear properties of ceramics are divided into creep,
hysteresis and non-linearity itself. Also nonlinear properties includes volatility and sens­
itivity of the piezo ceramic. Non-linearity and ambiguity of the dependence of the con­
trol voltage - the situation often leads to significant distortions of the image.
For the correction of displacement, many types of displacement sensors can be
used. It can be optical, inductive, magneto, capacitor, etc.
In the two-dimensional scanning stage Ratis, capacitive sensors are used. The op­
erating principle of such sensors are displayed in Figure 2.9.
Since, the capacity of a flat capacitor consisting of two parallel plates is given by
2.1:
С= 0
S
(2.1)
d
C – capacitance;
S – capacitance plates area ;
d – рlate distance ;
ε – dielectric factor;
ε0 – dielectric constant.
When the distance between the
plates changes the sensor capacitance,
offset of the axis can be measured.
“Nano Scan Technologies Ltd”
Fig. 2.9 Capacitance sensors diagram.
Certus – Scanning Probe Microscope. User manual
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