Probe Fiber Liquid Level Sensor Instrumentation Research

In this paper, a novel fiber-optic level sensor system has been developed. The system combines the features of high sensitivity of the optical fiber frustrated-total-internal -reflection based sensor and high positioning accuracy of the single chip computer controlled stepping motor driving system. The system can be applied to measure many kinds of liquid automatically and accurately including gasoline, diesel oil, benzene, etc. The sensor head is made from standard multi-mode communication silica fiber with a taper tip. There is sensitive response of the reflected light signal from the fiber taper when the refraction index of its surrounding medium changes. As the fiber taper is attached to the single chip computer controlled stepping motor driving device, the liquid level can be tracked and displayed continuously. The measuring resolution of 0.1mm and the accuracy of 0.4 mm have been achieved in a continuous measurement range of 2m. Further more, the system has a high reliability and without long term temperature drift due to the single fiber tip sensor head and level tracing mechanism.It is the first time that we introduce a high accuracy level sensing scheme combining the features of high sensitive optical fiber sensor and high positioning accuracy of the single chip computer controlled stepping motor driving system. The system supplies a new method for level measurement of many kinds of chemical liquids.In this paper, the design of the system is described in detail, including the selection of system device, the design of systematic circuit and software. The data acquisition, processing and control of the stepping motor are fulfilled with a single chip computer, and special considerations have been taken in the design of the systematic hardware and software for improving the anti-interference and reliability of the system.