Full-range, true on-line turbidimeter based upon optical fibers for application in the wine industry

This paper presents a new type of nephelometric turbidimeter capable of really functioning on-line, avoiding any type of sampling of the liquid to be measured and, as a result, not requiring valves, pumps or any other type of electromechanical device, which results in it lasting longer and reducing maintenance. In addition, it takes advantage of the possibility of light conduction via optical fibres to avoid the electrical parts coming into contact with or close proximity to the liquid; the use of optical fibres also avoids interference, improving the Signal-to-Noise ratio and offering remote measuring. This type of turbidimeter is for general application. However, the application is presented for measuring turbidity in the wine industry during wine-making processes, which presents added problems such as colour interference and the high interval of recordable values, which can reach levels of almost nil to over 4000 NTUs. The paper discusses the various possibilities for measuring turbidity that could be used, analyzing their advantages and disadvantages. Proposed solution uses direct light feedback and ratiometric measurement to guarantee a monotonic quasi-linear static transfer function. An experimentally verified alternative is suggested and is discussed in detail.