A New-style Plastic Optical Fiber Sensor Applied To Continuously Measure Liquid-level Change

Liquid-level sensor is an instrument used to detect liquid surface height. Therehave many liquid-level measurement methods. Foreign countries started more early inliquid-level measurement sensor, they put very abundant capital, their researchdeveloping very fast. At present, many foreign countries have developed many kindsof sensor which is full-featured, roboticized and with high accuracy. In China, thedeveloped measuring system that can be used in the actual production, it’s reliability,accuracy and functional are low than foreign, this need further development,especially for plastic optical fiber for the measurement of researches on the changeof liquid-level.In this paper, we made a liquid level sensor according to the basic principle ofthe optical fiber sensor. This paper mainly studies grade-index multi-mode plasticoptical fiber (GI-MM POF).Type: ESKA CK40. This kind of optical fiber’s diameter is1mm, fiber core’s diameter is980m, and cladding’s index is1.41, the fiber corerefractive index of1.492Optical fiber transmission of information mode is using light’s total reflectionin fiber, the information transmission from one end to the other side。Making theoptical fiber sensor is processing of optical fiber, make the light reflects out thefiber, reduce the total reflected light’s mode number, use of refraction of lightdetection changes in the external environment. When the outside environment change,namely when the outside refractive index change, the total reflected light’s modenumber can change, we can measure the changes of various parameters,some instrumentsin the terminal will show these changes at the end of fiber, so as to achieve the purposeof measuring external environment change. This paper mainly talks about optical fibersensor applied to measure liquid-level change. This paper’s method is carving a groove on optical fiber in the direction of thefiber by using of a machine tool. The depth and width of this kind of groove can beregulated on the basis of experimental conditions. The depth and width of groove whichpolished by this way are very uniform. This processing way of the optical fiber reducethe error brought by manually polish.In order to make it to be a sensor which can measure the height change ofliquid-level, we make the following treatment: Let the optical fiber coiled round auniform cylinder.(Pay attention to make the groove toward outside when winding thefiber, avoid results cannot be measured.）We put the main sensor in a large measuringcylinder, put the other sensor into a same empty cylinder. Take the same amount ofwater by a small measuring cylinder each time, record the number shown on anoscilloscope. Make a chart with the liquid surface height of the abscissa denotes,voltage strength shown on oscilloscope for ordinate. We see, voltage with liquid levelheight change has obvious change, then we can say that the new-style liquid-levelsensor is available. The deep groove depth, width is wider, the greater the bendingdegree, the higher the sensitivity of the sensor.