FISCHER Mess- und Regeltechnik GmbH
Product and functional description | 2
BA_EN_NC57
7/20
2.3 Intended use
The capacitive filling level probe NC57 serves to measure tank filling levels in
tanks containing fresh water, waste water or faeces. Filling level heights of
between 400 and 2000 mm can be measured. The probe can be used for tanks
made of metal.
Please contact the manufacturer before using this device with dirty or aggress-
ive media because the device needs to be adapted in terms of the parts that
come into contact with the media.
The device is to be exclusively used for the applications agreed between the
manufacturer and the user.
2.4 Function diagram
C
E
C
A
C
A
: Start capacity (probe free)
C
E
: End capacity (probe covered)
RxD
Min.
Max.
+U
b
-U
b
Output
brown
blue
black
IR
Status LED
Probe
µC
Earth connection
to the tank
Fig. 3:
Function diagram
2.5 Design and mode of operation
The tank wall and special rod form the electrodes of the measuring equipment.
A condition for the flawless function of the probe is a special probe mounted in
parallel to the tank wall. In the case of installation lengths > 700 mm, the rod
must be supported by insulated circlips at intervals of 700 mm respectively.
The housing is connected to the signal earth, and an AC voltage signal is ap-
plied to the special rod. If dipped into a fluid, this arrangement becomes a capa-
citor and the fluid acts as a dielectric. The capacity values of this capacitor are
proportional to the filling height of the tank. Electronics integrated into the
device convert these capacity changes into an analogue output signal (current
or voltage).
