No stress with stretch! Measuring the thickness of thin and transparent plastic films

Sensor Instruments GmbH: It is important to be able to measure the thickness of stretch films after production, including after the stretching procedure. The SPECTRO-MIR-10 measurement system enables fast and precise inline and offline measurement and is not affected by extraneous light.

The measurement principle is easy: mid-wavelength infrared light (MIR) is aimed at a reference metal plate, the majority of which is reflected in a diffuse manner. In addition to the broadband MIR light sources, which provide a homogeneous illumination of the measurement object at the respective measuring point, the front end of the sensor contains two detectors, each fitted with a narrow band wavelength window in the MIR range. The centre wavelengths of the two filters are offset; one of the two optical windows serves as a reference, i.e. the MIR radiation is not influenced by the presence of stretch films yet a significant reduction of the received signal can be observed in the actual measurement window. Placing the two signals in relation to each other produces an intensity-independent signal which alters with the thickness of the film in a reproducible fashion.

The Windows®-Software SPECTRO MIR Scope V1.0 can be used to calibrate the measurement system to the respective film type. In addition to the parametrization software, the monitoring software SPECTRO MIR Monitoring V1.0 is available, which is used to save measurement data and display it graphically and numerically, including trends.

Sketch: SI-MIR sensor, MIR light, plastic film, steel plate

The SPECTRO-MIR-10 measurement system permits quick, precise inline and offline measurements and is not affected by extraneous light

The SPECTRO MIR Scope Windows® software for parametrizing the measurement system