A well-known, but incomplete approach for a thickness measurement of oil is fuorescence. The oil is on a metal plate and it has to be removed by cleaning systems. This method works with an (in)visible light to detect the oil. The oil receives the light from the sensor which make the oil particles light up. A rule of thumb of this method is: the more intense the light, the thicker the oil layer.
In theory, this is a fine method to perform a thickness measurement of oil, because the oil is made visible. But you may already feel it coming: in reality and in practice things are different. Each type of metal and oil requires a different approach, if it even works.. So, the fluorescence method is limited in usability. And to make a note of every combination of oil and metal whether it works or not is cumbersome.
The correct solution: infrared sensors
You may be wondering; is there not a single method for thickness measurements of oil that works all the time? Good news, there is! The answer is infrared sensors. More specifically: infrared sensors with a middle-range wavelength. As it turns out, all oils react to a specific wavelength of infrared light.
Light is emitted onto the oil layer in this method as well. The difference lies within the type of emitted light and the way it is received by the sensor. The light, as stated earlier, has a specific wavelength and is infrared. Receiving the light is done by the two detectors that can be found on the sensor head of the SPECTRO-M-10-MIR infrared sensor. One detector is tuned to the specific wavelength to which the oil reacts (CH1). The other is congifured to another wavelength for a zero point measurement as a control (CH0).
To make the thickness measurement a success it is of utmost importance for the sensor from Sensor Instruments to be calibrated to the type of metal and oil. The oil type is decisive in the absorption rate of the emitted infrared light. This is simple because of the provided software.
Another application with infrared sensors is detecting and measuring the oil quantity on a metal surface.
