An application of instrumentation and control engineering for measurement of surface properties of liquids

摘要

Measurement of Surface Tension and kinetics of molecular aggregation process in surfactant solutions is an area for extensive experimental interdisciplinary research to establish the correlation of surface properties with technological applications such as foaming, emulsification and wetting of surfaces. Here, we present a methodology to determine the surface tension of distilled water with various customized Wilhelmy plates through the novel use of economic Tensiometer developed at Shah Schulman Center for Surface Science and Nanotechnology of D.D. University, India. There are several technologies which are used for the measurement of surface tension (force measurement). In commercial tensiometer available in market which works on EMF (Electromagnetic force) based technology, the advantage of this technology is that its repeatability and accuracy of this sensor is quite good as it is especially designed for very low force measurement but the limitation is that it is very costly. As a sensor, a platinum Wilhelmy plate used in commercial tensiometer, which increases the cost of the system while in the case of tensiometer developed at SSCSSNT of DDU, we have used customized load cell which is generally used for measurement of moderate to very high weight (grams to kilograms), due to bulk production and strain gauge used in the manufacturing of load cell, this sensor is cheaper but limitation is that when temperature changes (greater than 80°C) occurs, a nonlinearity comes in the measurement, at low range resolution is also less compare to EMF base sensor. For taking measurement at very low value of weight and to achieve accuracy below 5 milligram is also difficult in this kind type of sensor, hence special care should be taken at the time of measurement & mounting of sensor with electronic circuit board. In this Instrument, we have used sandblasted silver plate as a sensor which further reduces the cost. The entire system is connected with computer through RS232 serial communication, software program is designed in LabVIEW(Laboratory Virtual Instrument Electronic Workbench) which gives function like conversion of weight into surface tension, online monitoring with graph (Surface Tension Vs Time), storing peak value of surface tension, data logging (store the data