The Design On Fiber-Capacitive Drop Sensor

Liquid identification is to identify the components of tested liquid by technologies for such as density, tension and viscosity measurement. The contemporary ways of liquid identification mainly are IR Analysis Method, UV Analysis Method, Tension Analysis Method and Viscosity Analysis Method et. For the reason that those methods above are very complicated and devices are too expensive, the pervasive process of liquid identification is unbearably long and high-priced. These defects above can be remedied by Fiber-Capacitive Drop Sensor system (FCDSs) working in its operating range.The optical fiber drop sensor is a type of the liquid-testing sensors based on the relationship between the dripping process and the characters of the liquid to be tested. It is potentially useful testing systems of physical and chemical characters of liquid samples by analyzing the variety of the light intensity, termed as the fingerprint drop trace shortly FDT. The drop volume testing is based on the changing capacitive with the drop descending.Through to the research of every materials spectral absorption's characteristic, as well as the operating region of the photo rectifier, the light emitter diode and so on in the market, this article has selected the near-infrared light whose wave length is the 850nm-950nm to be the light source, and choosed using the sfh450 light emitter diode and the sfh250 photo rectifier as well as the diameter lmm plastic optical fiber. This article has designed the optical fiber electric capacity bubble sensor exhaustively, and given the drop head's mechanical drawing as well as the overall assembly drawing. In the procedure that test of sensor platform's build as well as in sensor's test, we temporarily used medical transfer line as the feed flow system to achieve the goal of forming the stable bubble. Moreover, this article also has introduced the method which gets out of the electric capacity two-pole lead wire draws, and the reduction of parasitic capacity and the outside photo source influence. Finally processing electric circuit through signal, we may obtain the light signal and the electric capacity signal which output is about the 7v, and the electric capacity signal assumes the good linearity, the light signal assumes two peaks and a trough.