Functional Principle, Technical Data; Measuring Principle; Capacitive Principle - MICRO-EPSILON combiSENSOR 64x0 Instruction Manual

Functional Principle, Technical Data

2.
2.1
The construction of the measurement coil and measurement electrodes is concentric. Both therefore measure
against the same target (measuring object). The signal of the capacitive displacement sensor is a function of
the working distance, the thickness of the insulator and e
sensor measures the distance to the ground electrode (for example flat sheet or to a metal roller positioned
behind the film). The measurements are output as analog voltages of 0 to 10 VDC and digital signals through
Ethernet or EtherCAT at the following controller.
2.1.1
The principle of capacitive distance measurement is based on the parallel plate capacitor.
If a constant AC current I
sor is proportional to the distance d between the capacitor electrodes.
U
Fig. 1 Electric field of a capacitive sensor, no insulator material in the gap.
The measured AC voltage is demodulated, amplified and output as an analog voltage. The sensor design
with guard ring electrodes guarantees that the ideally necessary homogenous electrical field is realized for all
practical purposes.
i
combiSENSOR 64x0
Functional Principle, Technical Data

Measuring Principle

Capacitive Principle

flows through the sensor capacitor, the amplitude of the AC voltage U
c
c
Ground
Screening electrode (guarding)
Measuring electrode
d
Measuring object: electrical conductor
A measurement object that is too small and curved (uneven) measurement surfaces also produce a
non-linear characteristic.
. At the same time the eddy current displacement
r
U
1
c
X = =
I d
C
I
c
c
U =
c
 
A
c
C =  
o
d
 r
at the sen-
c
>> U ~ d
A
c
r
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