Liquid level measurement in lab on a chip (LOC) devices is a challenging task due to the demand for a sensor with ultra-high resolution but miniature in nature. In this Letter, we report a simple, compact in size, yet highly sensitive liquid level sensor based on a hollow core fiber (HCF) structure. The sensor is fabricated by fusion splicing a short section of HCF between two singlemode fibers (SMFs). Sensor samples with different lengths of HCF have been studied; it is found that the sensor with a HCF length of ∼4.73  mm shows the best sensitivity of ∼0.014  dB/μm, corresponding to a liquid level resolution of ∼0.7  μm, which is over five times higher than that of the previous reported fiber optic sensors to date. In addition, experimental results have demonstrated that the proposed sensor shows good repeatability of measurement and a very low cross sensitivity to changes in the refractive index of the surrounding medium.

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Sub-micrometer resolution liquid level sensor based on a hollow core fiber structure

The popularity of Internet-of-Things (IoT) has provided us with unprecedented opportunities to enable a variety of emerging services in a smart home environment. Among those services, sensing the liquid level in a container is critical to building many smart home and mobile healthcare applications that improve the quality of life. This paper presents LiquidSense, a liquid level sensing system that is low-cost, high accuracy, widely applicable to different daily liquids and containers, and can be easily integrated with existing smart home networks. LiquidSense uses existing home WiFi network and a low-cost transducer that attached to the container to sense the resonance of the container for liquid level detection. In particular, our system mounts a low-cost transducer on the surface of the container and emits a well-designed chirp signal to make the container resonant, which introduces subtle changes to the home WiFi signals. By analyzing the subtle phase changes of the WiFi signals, LiquidSense extracts the resonance frequency as a feature for liquid level detection. Our system constructs prediction models for both continuous and discrete predictions using curve fitting and SVM respectively. We evaluate LiquidSense in home environments with containers of three different materials and six types of liquids. Results show that LiquidSense achieves an overall accuracy of 97% for continuous prediction and an overall F-score of 0.968 for discrete predication. Results also show that our system has a large coverage in a home environment and works well under non-line-of-sight (NLOS) scenarios.

Liquid Level Sensing Using Commodity WiFi in a Smart Home Environment

This paper presents the design of an instrument for measuring the liquid level. The objective of this proposed work is to measure the level of liquid accurately even with variations in liquid concentration. The designed instrument should also be able to compute the concentration of additives in the liquid. For this purpose, a multisensor model comprising a capacitive level sensor (CLS), ultrasonic level sensor (ULS), and capacitance pressure sensor is used to acquire information of the liquid. The data acquired from all these sensors are processed using Pau’s multisensor data fusion framework to compute the level of liquid along with the concentration of additives added to the solution. Pau’s framework consists of alignment, association function, analysis, and representation functions. The designed multisensor technique is tested with real-life data for varying liquid levels and additives. The results obtained show that the successful implementation of the proposed objective producing a root mean square of percentage error is 1.1% over the full scale is possible.

/pdf/design-of-an-instrument-for-liquid-level-measurement-and-72ffjeidfv.pdf

Design of an Instrument for Liquid Level Measurement and Concentration Analysis Using Multisensor Data Fusion

Ink printing is utilized to develop a coplanar capacitive senor with microscale electrodes, which exhibits high sensitivity. The sensor’s capacitance has been theoretically and experimentally correlated to the water resistivity. As a cost-effective, portable and reusable sensor, its application for water level measuring and quality monitoring has been demonstrated.

An inkjet-printed capacitive sensor for water level or quality monitoring: investigated theoretically and experimentally

A simplified economical liquid level measurement technique has been developed for measuring the level of any type of liquid. A fabricated inter digital capacitor (IDC) is used as a primary sensor that transduces the liquid head into corresponding variation in the capacitance. This variation in the capacitance changes to an electric signal, using a modified De Sauty bridge circuit. In this paper, different types of water, such as mineral water, tap water, distilled water, and river water, are used as process liquid. This sensor can be relied for the detection of the water level, independent of the water type. The theoretical analysis of the work has been illustrated in this paper to describe the working of the proposed transmitter. The proposed sensor has been developed and laboratory tested. It is found that this transmitter exhibited the linear characteristics and followed the theoretical equations. It has 12.8-mV resolutions for measurement of water level from 0 to 15 cm range.

Design and Development of an Electronic Level Transmitter Using Inter Digital Capacitor

A low-cost capacitive sensing device for liquid-level measurement is presented in this letter. We proposed a novel comb, such as pattern of electrode. An equivalent capacitor can be formed by the electrode and the liquid within the container, and the equivalent capacitance will be proportional to the area of the electrode. Therefore, when the liquid-level position reaches a larger area of the comb electrode, the equivalent capacitance will have significant gradient changes. The measurement results show a variation error of about 6%. The comb-electrode offers simple, effective, and accurate advantages without any additional calibration. This comb-electrode is easily to be applied to a non-intrusive monitoring system which can be found in various places around biomedical applications.

Low-Cost Comb-Electrode Capacitive Sensing Device for Liquid-Level Measurement

Noise cancellation is very important step for ECG signal processing. For this problem, there are many methods had been applied. For example, Wavelet based de-noises, EMD based de-noise, Kalman based de-noise, etc. for resource very limited system, the above method may be not fit into the system resource. Algorithm complexity and resource requirement will be the major concern in this work. In this paper, a new processing flow is proposed. it is combined two concepts, one is moving average and another is soft-thresholding. First, we will explain the whole process. Next, the performance will be discussed. And at the last, we will talk about the possible way to improvement the flow.

Huan Ke Chiu

Papers

Low-Cost Comb-Electrode Capacitive Sensing Device for Liquid-Level Measurement

ECG noise thresholding based on moving average