Water levels detected through labels
Tom Shelley reports on an infrared sensor well suited to bottling operations
An infrared sensor has been developed that allows the detection of water in a paste or glue through the sides of bottles, even through paper labels. The SA1W moisture sensor from Idec Electronics uses an infrared laser that works at a wavelength that is largely absorbed by water molecules.
It is well suited to ensuring the correct fill levels in a bottling plant but would also be able to detect the presence of water based adhesives in packing and carton forming machines or detect chemical solution in the bottom of a medical phial.
It can also detect the difference between oil and water, since oil appears relatively translucent at the wavelength used. If a transparent side arm is attached to a vessel containing oil and water, and the beam is aimed through it, it will be interrupted by the presence of water but pass straight through if it is oil.
Options include through beam and diffuse sensing and the use of fibre optics for smaller and more difficult to access targets. Sensing range is up to 800mm according to model and response time is 0.5s.
We have tested it on wine bottles, where it reliably detected whether contents were present. It worked with wine in either clear or coloured glass and through paper labels, even ones that were quite opaque to visible light. But, we imagine, that foil covered labels would likely cause a problem.
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