The document describes a measurement system using a confocal displacement sensor to measure liquid level during capacitor production. Key requirements were a measurement range of 24mm, accuracy of 50μm or better, and ability to measure a reflecting liquid surface in an explosion-hazard area. The optoNCDT 2400 confocal sensor was selected due to its non-contact measurement, high accuracy against reflecting surfaces, and easy mounting in a protective housing with sealing to isolate it from explosive vapors. The system ensures individual capacitor components meet quality criteria by maintaining an exactly defined dipping depth.

1. A151_e
Confocal displacement sensors
optoNCDT 2400
Liquid level measurement during capacitor production
During the production process capacitor elements Measurement system requirements:
must be dipped in a defined manner into a bath of - Measurement range: 24 mm
liquid. To ensure constantly high quality it is crucial - Required accuracy: 50 µm
that the capacitor elements are dipped exactly - Accuracy obtained: 10 µm
according to the specification. Therefore, it is of the - Measurement on: Reflecting surface
utmost importance that the liquid level is maintained - Material: Solvent, reflecting
at a very accurately defined height. - Ambient conditions: Area subject to
For these measurements conventional laser triangu- explosion hazards due to solvent vapors
lation sensors required a complicated system setup
and their complex adjustment incurred costs. The Measurement system setup: optoNCDT 2400
wave motion of the liquid that occurred interrupted - IFC2400 controller
the measurement signal which could not then be - IFS2400-24(01) sensor for 24 mm measurement
used for further evaluation. range and additional V4A sealing ring
To compensate these shortcomings, a confocal (Ex protection)
sensor of the Series optoNCDT2400 was employed. - C2400-10 sensor cable 10 m long
By means of the confocal principle this system
measures to the directly reflecting surface of the Reasons for the system selection
solvent. The explosive vapors are kept away from the - Non-contact measurement
sensor since it is inserted into a protection housing - Highly accurate against directly reflecting target
with a sealing ring and an O-ring seals the optical - Easy, precise sensor mounting
system. In addition the conduit is constantly heated
externally to prevent condensation forming on the
optical system.
Protection housing
This measurement arrangement ensures that due to Confocal sensor
an exactly defined dipping depth the individual
Sealing ring
components conform to the defined quality criteria, Lens
such as for example the shelf-life or safety under O-ring
short-circuit conditions.
Measurement of the filling level
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