Low Capacitance Measurements Research Articles

Smart system for cavitation cause measurement and control in irrigation pump

The objective of this study is to develop an effective smart system for cavitation cause measurement and control in pump units. An analysis of the known sources of measurement and control of the cavitation shows that the known methods are based on the measurement of the effects of causing cavitation such as vibration, temperature and pressure changes in the pipeline. The proposed smart cavitation cause measurement and control system is based on converting water- air ratio to the electrical signal by means of capacitance sensor that has very low value. The electrical scheme of low capacitance measurement by means of modern microcontrollers, block diagram and algorithm of smart system for cavitation cause measurement were developed. The complete smart system for cavitation cause measurement and control by means of modern microcontrollers was implemented in hardware and conducted experiments. The theoretically and experimentally obtained capacitance and the water - air ratio relationship is presented. Based on experimental studies, the relative error of the measurement system was determined and its graph is submitted.

A high voltage method for measuring low capacitance for tomography

Low capacitance measurement is involved in many industrial applications, especially in the applications of electrical capacitance tomography (ECT). Most of the low capacitance measurement circuits employ an ac-based method or a charge/discharge method because of high sensitivity, high resolution, and immunity to stray capacitance; and its excitation or charge voltage are not more than 20 V. When ECT techniques for large industrial equipment such as blast furnaces or grain barns are explored, the existing methods for measuring low capacitance have some limitations. This paper proposes a high excitation voltage ac-based method for measuring low capacitance to improve the resolution of measurement. The method uses a high excitation voltage of several hundred volts and a transformer ratio arms as the C/V transducer. Experimental results indicate that the new method has a resolution of 0.005 fF, a good stability (about 0.003 fF over 4 h) and linearity (0.9992).

A method for measuring low capacitance for tomography

The applications of electrical capacitance tomography (ECT) to image multiphase flows in pipelines, fluidization process, interfaces in separation vessels, and combustion phenomena in internal combustion engines have been studied for some years. In these applications, none of the equipment imaged has an inner diameter exceeding 1 m. When ECT techniques for large industrial equipment like blast furnaces are explored, the existing methods for measuring low capacitance have some limitations. This article proposes a method for measuring low capacitance which is suitable to construct ECT systems for imaging large industrial equipment. The method is based on single high-voltage excitation and magnetic C/V converting principle which can resist interference by stray capacitance. Experiment results indicated that the method has good performance in regard to resolution, linearity, and stability. Though the method was designed for imaging large equipment, it can also be applicable to other fields where low capacitance measurements are required.