Hidam Kumarjit Singh

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

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 μm and 6.2 μL, 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.

Truly Nonintrusive Liquid-Level-Sensing Method Based on Lateral Displacement Effect of Light Rays

A truly nonintrusive optical sensing method suitable for accurate and precise measurement of liquid level is proposed and demonstrated in this paper. Sensing principle of the proposed method is based on the phenomenon of lateral displacement effect, which is observed when oblique light rays propagate through material media with different thicknesses and refractive indices. Experimental results of this method demonstrate its ability to measure liquid level very precisely up to a resolution of about 40-50 μm. The proposed method has the potential for use in in situ measurement of liquid level and volume. It can also be exploited for measurement of refractive index of liquid.

Non-Intrusive Technique for Measuring Refractive Index of Clear and Transparent Liquids

We propose an optical technique for measuring refractive index of clear and transparent liquids. This technique senses change in refractive index of liquid by virtue of lateral displacement of a light beam that occurs due to refraction of the light beam after passing through the liquid medium. The transmitted light beam gradually looses its alignment with a photodetector as refractive index of the liquid changes. Experimental results have indicated that the proposed technique has the potential to measure refractive indexes with an accuracy of 10-4, and it has novelty of being a simple and non-intrusive one.

Micro-controller based frequency to digital converter for interfacing frequency output sensors

We present the design and testing of a 16-bit frequency to digital converter, based on AT89C51 micro-controller, for use in sensing applications. The system generates digital equivalents of frequencies by counting negative transitions of transistor transistor logic signal applied to a designated input of the microcontrollers on-chip counter. The system digitizes frequencies of signal generated from a frequency generator, while the digitized data are logged in a personnel computer via printer port by using a LabVIEW program. The system is found to have a linear response over a large dynamic range of conversion, and its resolution is tunable down to 1.6 Hz. The proposed system can be used as interface circuit for frequency output sensors without relying on frequency to voltage converter and analog to digital converter.

Fiber-optic liquid level sensor based on coupling optical path length variation

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm.

Fiber Optic Sensor for Liquid Volume Measurement

In this letter, we report a novel fiber optic sensor, which will be suitable for precise determination of volume for any type of liquid present inside a container. The sensor uses a circularly bent fiber loops to sense variation of liquid volume by exploiting bending loss phenomenon. Experimental observations have confirmed that the sensor is able to measure liquid volume down to resolution of 71±3.5 μL.

Cobalt chloride doped polymer film for relative humidity measurement

We report a simple approach to measure relative humidity with high dynamic range and fast response time using Cobalt chloride (CoCl2) doped polymer thin film. Anhydrous Cobalt chloride exhibits high absorption at low humidity level in the wavelength range 550-700 nm while possess very low absorption at high humidity level present in the environment. Thin CoCl2 doped polymer films of different thickness were fabricated on thin cover slides using dip coating technique. Expanded light from a diode laser source (680 nm) was allowed to transmit through the sensing film of the slide. The variation in intensity of the transmitted light with the moisture level present in the environment was monitored using silicon photodiode and finally the detector signal was taken through a computer. As large area of the sensing region is exposed to the environment, high sensitivity of the sensor is achieved. Further, sensor response was investigated in terms of chemically synthesized film thickness on the slides. A high dynamic range of the sensor is obtained with fully reversible and repeatable behavior. The advantage of the system is its simplicity and is a very low cost technique to monitor relative humidity present in environment.

Fiber Optic Viscometer Based on Sliding of Liquid Drop Under Gravity on Inclined Flow Channel

We report a fiber optic sensor for measuring the viscosity of Newtonian liquids. The sensing principle of the proposed sensor is based on sliding of liquid drop on an open air channel during which the liquid interacts with two decladded regions of an optical fiber. When liquid slides over the first decladded region, transmitted light intensity of the fiber undergoes an upward transition. As the liquid again slides over the second decladded region, another upward transition occurs. The time interval between the two transition events is known as transition time of the proposed sensor, and it is found to increase with increase in viscosity of the liquids when longitudinal displacement between the decladded regions and inclination of the flow channel are held constant.

Fiber Optic Sensor for Detection of Chlorine Level in Water

We report a fiber optic sensor to measure the level of free chlorine present in chlorinated water. The sensor is made of an optical fiber that has been suitably bent in the form of U-shape. The sensor produces its sensing action when the U-shape probe is dipped inside liquid samples. Sensing principle of the sensor is based on absorption of fiber optic evanescent light wave by surrounding liquid medium. Experimental observations have shown that sensitivity increases with decrease in wavelength of excitation light source. We found that resolution of the sensor varies from 2.7 to 5.5 mg/L at 430 nm wavelength. The proposed sensor has the potential to be a low-cost alternative device for measuring free chlorine level of chlorinated drinking water very precisely and accurately.

Design and Implementation of Portable and Compact Human Heartbeat Rate Monitoring System

In this paper, we proposed a portable, compact, and low-cost heartbeat rate measuring system by using optical sensor. Our proposed device can be used by common people during outdoor physical activities, e.g., during morning walk, for different outdoor exercises, and for various sports-related activities. The design aspects and preliminary results of the system are presented here.