A New Non-Intrusive Optical Technique to Measure Transparent Liquid Level and Volume

Abstract

We report here a novel optical technique for the continuous measurement of the level and the volume of transparent liquids in a cylindrical container. This measurement technique is based on the principle of liquid level induced modulation in the solid angle of a divergent light beam incident on liquid surface. This technique has advantages of being a very sensitive and non-intrusive way of measurement. The proposed technique has been experimentally tested with clean water, colored water, diluted glycerin, and pure glycerin by using liquid containers having 100-, 250-, and 500-mL capacity. Measurement results provide the highest sensitivity in the case of a container having smallest diameter. The proposed system is capable of measuring the liquid level and volume with approximate resolutions down to 3.2 m and 6.2 L, respectively, in the case of a 100-mL container. The sensitivity is found to decrease with the increasing diameter of the container as well as with the decreasing optical transparency of the liquids, but increase with the increasing refractive indices of transparent liquids. And this technique has an appreciably larger dynamic range of measurement, good linearity, and repeatability in the measurement responses.

Design of a low cost signal conditioning circuit for self-compensated non contact capacitive type multi threshold liquid level sensor

“…The optical sensors (fiber optics, γrays), ultrasonic sensors etc. belonging to the non-contact type liquid-level measurement methods as in [1][2][3][4][5][6] are not suitable for measuring liquid level through a container without contacting the liquid. Further, these are very complex and expensive because of their associated electronic circuit.…”

Fiber optic sensing system for in-situ simultaneous monitoring of water stage, quality, and temperature

“…Both noncontact and contact sensing methods are available for optical water level sensing. Noncontact optical water stage sensing devices, including laser based [5], and light-emitting diode (LEDs) based sensors [6], began to attract industry attention in the early 1970's .The noncontact LED-based optical sensors have eliminated effects on optical properties of the monitored water leading to the possibility for multiparameter sensing [7]. However, in order to achieve an accurate measurement, this technique requires a large number of LEDs and phototransistors, resulting in a costly solution.…”

Contactless liquid-level measurement through opaque container using millimeter-wave sensor

“…There is a large variety of methods for liquid-level measurement, ranging from electrical sensors, mechanical floats, and fiber optics to ultrasonic methods [1][2][3][4][5][6]. Most of these methods, however, are not suitable for measuring liquid level through an opaque container without contacting the liquid.…”

“…A capacitive semi-cylindrical sensor mounted around a liquid container can measure liquid level without contacting the liquid [2], but its measurement accuracy is not high because the capacitance is strongly dependent on the distance between a container and a sensor. Consequently, optical sensors [3,4] are not suitable for measuring the level of liquid in opaque containers or containers with labels.…”