Design, development and application of a real-time capacitive sensor for automatically measuring liquid level

Abstract

In the present study a real-time capacitive sensor based on a capacitance step method is designed, developed and applied on measuring the liquid level by immersion. The capacitive sensor consists of two electrodes from copper plated phenolite plates separated by a gap distance and mounted inside a non-conductive storage tank. Water is used as the dielectric material. The analyzed sensor behavior with liquid level variation is semi-linear and obtained in function of the output voltage variation by using proper signal conditioning circuit. For converting the voltage variation into level variation, a parallel R-C circuit is used instead of conventional bridge circuit. Under suitable parameter settings it provided good reading accuracy. The experimental results demonstrate the high efficiency of the proposed model, which confirm the satisfactory performance of the capacitive sensor for liquid level measurement. The sensor presents an excellent ease of construction and installation, linked to the good measurements precision and high autonomy of system operation. The behavior experiments under different salt concentrations show that the water chemical composition does not interfere on the sensor operation. The proposed model exhibits a promising employment in several applications, such as control equipment for irrigation, biomedical area-in the interaction between antibody-antigen or protein-DNA, aerospace and pharmaceutical industry, gas sensors, and automation solutions.

A non-reference detection method of the external ultrasonic liquid level switch using the PZT

“…There are many LLS technologies including: floating ball LLS [5], cable float LLS [6], capacitive LLS [7], tuning fork LLS [8], ultrasonic LLS [9], external ultrasonic LLS [10], etc. Among them, the external ultrasonic LLS is a new type of level measurement alarm device, which is installed outside the tank, no need to open holes in the tank, and non-contact measure.…”

Capacitive, Non-Invasive and Coplanar-Electrode Transducer for Measuring Iron Ore Moisture

“…For this, a capacitive transducer of non-invasive coplanar electrodes is presented. The main differences of this research in relation to other works on the existing area and commercial equipments are: (i) the embedded construction of all elements of the measurement system in a single compact hardware; (ii) the arrangement of the electrodes in a coplanar form that assists in system coupling to ore flow monitoring applications; and (iii) the oscillating circuit method [7][8][9] applied to iron ore moisture monitoring, which adds a high cost-benefit ratio compared to other techniques, such as those using high frequency.…”