Liquid Level Measurement Research Articles

Design of and research on industrial measuring devices based on Internet of Things technology

With the development of communication technology and the coming of Industry 4.0, Internet of Things (IOT) devices are being widely applied in industry and manufacture. In this paper, wireless industrial devices based on the IOT are investigated. Sensor technology and wireless technology are regarded as the development trends of the industrial IOT. Therefore, we designed and studied three kinds of industrial wireless monitoring and measuring devices whose core components are capacitive sensors. These devices can be applied to paper measurement, gesture recognition and liquid level measurement, which address three industrial requirements. Each device is designed with a complete structure, and they can operate automatically and independently. Each sensor device is a node of a wireless network and a component of an industrial dynamic detection network. The purpose of this research is to propose several models of wireless industrial measurement devices that are helpful for real-time industrial monitoring and that improve the efficiency of industrial production.

Application of 3D printed polymer composite as capacitive sensor

PurposeThe purpose of this study is to demonstrate the usage of three-dimensionally (3D) printed polylactic acid (PLA)-carbon black (CB) conductive polymer composite in the measurement of the void fraction and liquid level.Design/methodology/approachPLA-CB conductive polymer composite is 3D printed through fused deposition modelling (FDM) technique and used as a capacitive sensor for void fraction measurement and liquid level sensing. The sensitivity of 3D printed ring and concave type capacitive sensors are compared for void fraction measurement. The effect of electrode length, thickness and pipe dimension on the capacitance achievable for the particular void fraction is studied. Concept of fringing capacitance is used for the sensing of liquid level.FindingsCompared to the concave design comprising four electrodes, the ring-type capacitive sensor produced better results in void fraction measurement. Increase in pipe diameter and electrode length results in the enhancement of capacitance arising from specific void fraction. For a 100 mm diameter pipe, the capacitance of the 150 mm-long concave electrode (0.4 mm thick) increased from 9.98 to 67.77 pF as the void fraction decreased from 100% to 0%. Development of the fringing capacitance in 3D printed PLA-CB composite helps in the measurement of liquid level. Both parallel finger topology and interdigital electrode configuration are able to sense the liquid level.Originality/valueAbility of the 3D printed conductive PLA-CB composite to act as a capacitive sensor is experimentally analysed. Performance of different electrode configuration is tested for both void fraction measurement and liquid level sensing. Results of experimentation prove that FDM printed PLA-CB composite is suitable for the void fraction and liquid level measurement.

Optical spectral intensity-based interrogation technique for liquid-level interferometric fiber sensors.

In this paper, we propose a new, to the best of our knowledge, technique based on the measurement and analysis of the intensity of the interference pattern as an alternative approach for interrogating liquid-level interferometric fiber sensors. This interrogation is based on calculations that can take into account a vast number of peaks and dips of an interferometric spectrum, allowing the use of such devices as distributed sensors capable of measuring longer-level ranges. Here, liquid-level measurements of up to 120 mm were experimentally obtained with high linearity and a sensitivity of $ - {0.042}\;{\rm dB/mm}$-0.042dB/mm.

Characterization of Pressure Sensor for Liquid-Level Measurement in Sloshing Condition

To achieve a reliable and accurate liquid-level detection, a differential pressure-based instrument is proposed in this article. The phase-sensitive demodulation of the signal is performed by the discrete Fourier transform (DFT) through a microcontroller. A good linearity in both ac and dc measurements has been observed. AC-based-level sensing demonstrated reliable and robust-level detection compared with dc, in both steady state conditions and while experiencing turbulence on the surface. In addition, thermal behavior of the proposed instrument is characterized and compensated, in order to evaluate its uncertainty as a liquid-level sensor. The obtained results show a combined uncertainty lower than 1 mm, which is mainly limited by sloshing conditions.

Wireless simultaneous measurement system for liquid level and density using dynamic bubbler technique: Application to KNO3 molten salts

We have developed a liquid level measurement system using the dynamic bubbler technique. Based on our previous methodology, herein, we established a field-applicable wireless measurement system to simultaneously monitor the liquid level and density of corrosive molten salts at high temperatures. The accuracy and precision of the present technique were suitable for applications in harsh field processes. Regardless of the base pressure under the present experimental conditions, percentage differences compared with reliable reference values in the literature were less than 10% in the temperature range 773–1123K using KNO3 as a molten salt. Our dynamic bubbler technique produces an average percentage difference ca. 5–8% with a standard deviation of less than ca. 0.04gcm−3 between measured and literature density values in all experiments, whereas the standard deviations in all liquid level measurements were less than 0.3mm (0.07% relative standard deviation). The present technique is an excellent alternative to many conventional liquid level and density measurement techniques used under extreme environmental conditions characteristic of common industrial processes.

The Role of Millimeter-Waves in the Distance Measurement Accuracy of an FMCW Radar Sensor.

High-accuracy, short-range distance measurement is required in a variety of industrial applications e.g., positioning of robots in a fully automated production process, level measurement of liquids in small containers. An FMCW radar sensor is suitable for this purpose, since many of these applications involve harsh environments. Due to the progress in the field of semiconductor technology, FMCW radar sensors operating in different millimeter-wave frequency bands are available today. An important question in this context, which has not been investigated so far is how does a millimeter-wave frequency band influence the sensor accuracy, when thousands of distance measurements are performed with a sensor. This topic has been dealt with for the first time in this paper. The method used for analyzing the FMCW radar signal combines a frequency- and phase-estimation algorithm. The frequency-estimation algorithm based on the fast Fourier transform and the chirp-z transform provides a coarse estimate of the target distance. Subsequently, the phase-estimation algorithm based on a cross-correlation function provides a fine estimate of the target distance. The novel aspects of this paper are as follows. First, the estimation theory concept of Cramér-Rao lower bound (CRLB) has been used to compare the accuracy of two millimeter-wave FMCW radars operating at 60 GHz and 122 GHz. In this comparison, the measurement parameters (e.g., bandwidth, signal-to-noise ratio) as well as the signal-processing algorithm used for both the radars are the same, thus ensuring an unbiased comparison of the FMCW radars, solely based on the choice of millimeter-wave frequency band. Second, the improvement in distance measurement accuracy obtained after each step of the combined frequency- and phase-estimation algorithm has been experimentally demonstrated for both the radars. A total of 5100 short-range distance measurements are made using the 60 GHz and 122 GHz FMCW radar. The measurement results are analyzed at various stages of the frequency- and phase-estimation algorithm and the measurement error is calculated using a nanometer-precision linear motor. At every stage, the mean error values measured with the 60 GHz and 122 GHz FMCW radars are compared. The final accuracy achieved using both radars is of the order of a few micrometers. The measured standard deviation values of the 60 GHz and 122 GHz FMCW radar have been compared against the CRLB. As predicted by the CRLB, this paper experimentally validates for the first time that the 122 GHz FMCW radar provides a higher repeatability of micrometer-accuracy distance measurements than the 60 GHz FMCW radar.

Plastic fiber optic sensor for continuous liquid level monitoring

The study demonstrates the development of a novel low-cost plastic optical fiber (POF) based sensor for liquid level measurement. The sensor works on the principle of reduction in scattering-based optical losses (in contrast to the increase in optical losses for evanescent wave-based sensing) in a straight decladded fiber with an increase in the liquid level due to refractive index changes in the medium surrounding the fiber. A compact optical setup is developed in-house consisting of two U-bent fiber probes coupled to a single LED on one end and two photodetectors on the other ends to measure the optical intensity changes. One of the U-bent probes is decladded over the length of the fiber to act as a test probe to measure the liquid level, while the other probe acts as a reference to compensate for the light intensity fluctuations due to light source instability and ambient conditions. The difference in voltage responses of the two photodetectors gives a measure for liquid level. We have investigated the fiber optic level sensor response to rising and falling liquid levels over 55 cm in presence of aqueous liquids of different refractive index values (1.33 to 1.38) and 95% ethanol as well as DI water at various temperatures from 16 °C up to 70 °C. A level sensitivity of 1.4 and 3.3 mV/mm for water level changes was obtained for the liquid level below and above 45 cm respectively. In addition, the fiber optic level sensor shows a stable and reproducible response over several cycles of 30 min duration at different liquid levels. The results demonstrate that this fiber optic level sensor is not only easy-to-make, cost-effective and robust but also offers sensitive, stable and reproducible instantaneous level measurements.

Optical Fiber Specklegram Chemical Sensor Based on a Concatenated Multimode Fiber Structure

An optical fiber specklegram chemical sensor based on a concatenated multimode-no-core-multimode structure is reported. The 30 mm-no-core section is immersed in the analyzed liquid so the number of excited modes is modulated by the surrounding refractive index value, affecting the interference of the several propagating modes and consequently the output specklegram, whose changes are quantified by the zero mean normalized cross-correlation coefficient. The sensor was evaluated on the measurement of ethanol-water solutions, resulting in 18.7 RIU $^{-1}$ sensitivity (5 × 10−4 resolution) for the 1.33 to 1.36 refractive index interval, besides 0.07 $^{\circ }$ C $^{-1}$ temperature sensitivity within the 26–32 $\,{}^{\circ }$ C range. Moreover, the system was also tested on liquid level measurements, yielding 0.05 mm $^{-1}$ sensitivity and 0.2 mm resolution. The results are comparable to previously reported multimodal interferometers based on more complicated interrogation schemes, indicating that the specklegram sensor is a feasible alternative for the sensitive and straightforward measurement of liquid samples.

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

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

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.

Liquid level measurement based on multi-S-bend plastic optical fiber

PurposeThis paper aims to propose a liquid level sensor with a multi-S-bend plastic optical fiber.Design/methodology/approachThe principle of liquid sensing used is based on the leakage of higher modes out of the fiber and repeated regeneration in the following bend sections. Therefore, a propagation loss was introduced in every bend section of the fiber with the loss depending on the refractive index of the environment.FindingsTherefore, a continue shift in the liquid level can be detected by observing changes in the propagation loss of the fiber. The sensor features compactness and a flexible resolution.Originality/valueCompared with the exited ones, the sensor has capability of continue liquid measurement and a greater measurement range.

Optical fiber liquid level sensor realized by cascading two spherical-shape structures

An optical fiber sensor for liquid level measurement of NaCl soultion based on Mach-Zehnder interferometer (MZI) is proposed and demonstrated. The MZI consists of two spherical-shape structures. The simulations of the light propagation of the spherical-shape structure with different diameters are performed, and it shows that the spherical-shape structure with diameter values of 200 μm can couple 50% energy of the core-mode into the cladding mode, and it is helpful to obtain best interference contrast. The liquid level sensitivity is -1.172 nm/cm for pure water, and -1.401 nm/cm for NaCl solution(n = 1.382). The sensor has advantages of easy fabrication, good robustness, and low hysteresis.

Advances on Photonic Crystal Fiber Sensors and Applications.

In this review paper some recent advances on optical sensors based on photonic crystal fibres are reported. The different strategies successfully applied in order to obtain feasible and reliable monitoring systems in several application fields, including medicine, biology, environment sustainability, communications systems are highlighted. Emphasis is given to the exploitation of integrated systems and/or single elements based on photonic crystal fibers employing Bragg gratings (FBGs), long period gratings (LPGs), interferometers, plasmon propagation, off-set spliced fibers, evanescent field and hollow core geometries. Examples of recent optical fiber sensors for the measurement of strain, temperature, displacement, air flow, pressure, liquid-level, magnetic field, and hydrocarbon detection are briefly described.

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

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.

Ultrasonic waveguide based level measurement using flexural mode F(1,1) in addition to the fundamental modes.

This paper reports on an ultrasonic waveguide sensor for liquid level measurements using three guided wave modes simultaneously. The fundamental wave modes longitudinal L(0,1), torsional T(0,1), and flexural F(1,1) were simultaneously transmitted/received in a thin stainless steel wire-like waveguide using a standard shear wave transducer when oriented at an angle of 45° to the axis of the waveguide. Experiments were conducted in non-viscous fluid (water) and viscous fluid (castor oil). It was observed that the flexural F(1,1) wave mode showed a change in both time of flight (due to the change in velocity and dispersion effects) and amplitude (due to leakage) for different levels (0-9 cm) of immersion of the waveguide in a fluid medium. For the same level of immersion in the fluid, the L(0,1) and the T(0,1) modes show only a relatively smaller change in amplitude and no change in time of flight. The experimental results were validated using finite element model studies. The measured change in time of flight and/or the shift in central frequency of F(1,1) was related to the liquid level measurements. Multiple trials show repeatability with a maximum error of 2.5% in level measurement. Also, by monitoring all three wave modes simultaneously, a more versatile and redundancy in measurements of the fluid level inside critical enclosures of processing industries can be achieved by compensating for changes in the fluid temperature using one mode, while the level is measured using another. This ultrasonic waveguide technique will be helpful for remote measurements in physically inaccessible areas in hostile environments.

An Acoustic Resonance-Based Liquid Level Detector With Error Compensation

In the liquid level measurement principle based on acoustic resonance, level height is usually calculated via the detected fundamental resonance frequency (RF), which limits that the upper limit of measurement range is only about 8.28 m when air is a gas medium. In order to increase the measurement range, a new liquid level detector is presented using a group of RFs generated in a given frequency range instead of the single fundamental RF. The measuring accuracy of the detector can be improved by the use of error compensator based on belief rule base. This compensator enables the detector to learn compensation values from reference detection cycles; therefore, such a system is flexible and can be easily optimized under specific operating conditions. The experimental gauge is built by using low-cost components including a speaker, a microphone, a thermometer, a waveguide, a controller, and tested within a wide range with the upper limit reaching to more than 10 m. It has a better overall performance than that of the original detector.

Simultaneous measurement of three parameters based on an up-tapered fiber cascaded with a droplet-like multimode interferometer

In this paper, an up-tapered fiber (UTF) cascaded with a single-mode-fiber (SMF)-formed droplet-like multimode interferometer (DLMI) for simultaneous three-parameter measurement is proposed. In our setup, a segment of coating-stripped SMF is bent into a droplet-like structure. A UTF is introduced in front of a leading-in SMF of DLMI to enhance the excitation of high-order cladding modes in SMF due to its much bigger divergence angle like a convex lens. As a result, three sets of main interference between fiber core mode and cladding modes appear and then are recovered respectively by use of Fourier-transform-interrogation-based technique. Due to the fact that each recovered interference component of the sensor responses differently to the changes in liquid level, surrounding refractive index (RI) and temperature, simultaneous liquid level, surrounding RI and temperature measurement is achieved, with maximal sensitivity of −154.00 pm/mm, −132.47 nm/RIU, 238.97 pm/°C respectively. The all fiber sensor we proposed is simple, easy fabrication and low cost, especially with better mechanical strength and suitable for practical applications.

In brief

PAGE 274 Internet use on aircraft is prohibited with current RF wireless communication technologies but a team of researchers in Italy is proposing to use visible light communications as an alternative to enable access. Reading lights are investigated as signal source emitters to user devices and the minimum capacities needed to practically implement such a system are reported. PAGE 244 A pair of researchers in the UK have proposed a novel combination of wireless and conventional metallic interconnects to improve the performance of an on-chip clock distribution. Their results show a dramatic reduction in total delay compared with other advanced models and demonstrate that some clock uncertainties become predictable. Perspective view of Airbus A320 cabin model. PAGE 278 An optic fiber one-piece flexible sensing probe for liquid level sensing in cryogenic propellant tanks has been presented by researchers in China. The probe is ultra-lightweight and provides advantages over currently existing models in gauging accuracy, reliability, simplicity and maintenance with results from the measurement of liquid nitrogen levels. Proposed hybrid wireless architecture. PAGE 282 Researchers from China have successfully demonstrated the high performance of a normally-off recess-gated AlGaN/GaN metal-insulator semiconductor field-effect transistor (MISFET) with an operating temperature of 200°C. The device was fabricated using a self-terminating gate recess etching technique and states the highest reported value for an off-state gate breakdown voltage for a normally-off device operating at this temperature. Schematic experimental setup for measurement. PAGE 288 A new symbol detection scheme for uplink wide-banded cyclic prefixed filter bank multiple access (CP-FBMA) systems has been proposed by researchers in China. The new scheme has the benefits of lower complexity and higher spectral efficiency due to a feature that eliminates the analysis filter bank processing that is commonly employed in existing schemes. Cross-section of the AlGaN/GaN MISFET. BER curves of different systems.

Bernoulli-Euler finite-element modelling of vibration modes on axisymmetric containers for level measurement

Liquid level measurement inside closed containers is an essential process in control systems, quality control, and many real scenarios in the daily life. In this work, an analysis of vibration modes behavior of two axisymmetric containers and an immersed beam, aiming to liquid level measurement using acoustic resonance, is presented. In acoustic resonance, the vibration pattern produced in the container when it is excited by an external force is related to the liquid level and its physical characteristics. Vibration modes are analyzed using Bernoulli-Euler approach and finite-element modelling (FEM) in COMSOL. Results show a good correspondence of normalized frequency vibration modes shifting vs liquid level. Experimental results are consistent with theoretical and simulated FEM analysis, with an error lower than 1% in the first longitudinal vibration mode.

A review on liquid level measurement techniques using mathematical models and field sensors in blast furnace

Stable blast furnace operation requires proper drainage of liquid from the hearth. The estimation of drainage rate and hearth liquid level are of utmost importance for understanding the underlying hearth phenomena. The present review gives an insight of the need for measurement of the hearth liquid level and further throws light on various methods of estimation of hearth liquid level in-depth, which is primarily divided into 2 categories namely; model-based estimation and sensor-based estimation. Although the model-based estimation and sensor-based estimation have their own advantages and disadvantages, an integrated system comprising of both methods could potentially facilitate operators to reveal the state of hearth, which is unless not available with the implementation of a single method of estimation. Furthermore, the challenges in the estimation and the prospects for determining the reliable hearth liquid level measurement in blast furnace are discussed. The article is presented to give prospect of encountering the drift occurring in estimation of liquid level, which leads to inaccurate prediction and simulation with the industrial blast furnace. Lastly, the article gives recommendation for improving the liquid level estimation methods in blast furnace.