2 | Product and functional description
FISCHER Mess- und Regeltechnik GmbH
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BA_EN_ME50_ATEX
2.4 Function diagram
SP1
SP2
1.234
µC
þ û ÿ
D
A
1
2
3
5
6
7
8
Aout
4
Fig. 1:
Function diagram
1
Sensor
2
Signal converter
3
Switching outputs
4
Analogue output
5
Measured value display
6
Keyboard
7
Microcontroller
8
Pressure equalisation
2.5 Design and mode of operation
Depending on the measuring range, the ME50 is produced with a ceramic or a
piezo-resistive measuring cell. Two switch outputs are also possible in the ver-
sion with a 3-conductor connection.
Ceramic measuring cell
In the ceramic measuring cell, the pressure acts directly on the ceramic mem-
brane which in turn deforms. The membrane is constructed electrically like a
plate capacitor whose capacity change is proportional to the effective pressure.
The electronics that are controlled by a micro-controller implement this change
in capacitance into an standard electrical signal.
Piezo-resistive measuring cell
In the piezo-resistive measuring cell, the pressure is applied to a silicon mem-
brane into which the deformation-dependent resistances have been diffused.
The material resistance changes proportionally to the effective pressure. The
electronics that are controlled by a micro-controller implement this change in
resistance into an standard electrical signal.
