Optical Liquid Level Sensor Research Articles

Alat Pengukur Ketinggian Air Pada Landasan Pacu Pesawat Dengan Metode Image Processing

An aircraft accident are caused by several factors, one of which is the weather. High rainfall causes the runway to become slippery and wet. This will cause hydroplaning events on the plane. Hyproplaning is a skidding event caused by puddles of water on the runway. The maximum height of puddles on the runway is 3 mm. Currently, to measure the water level is still done in a conventional way and there is no sensor capable of measuring the water level in mm. To prevent accidents due to hydroplaning, a measuring device is needed that can monitor the water level in millimeters and has a long size range and is calibrated on the runway. This water level meter is made using a raspberry Pi 3 B+ miniPC. The stages in making this tool include hardware design and software design. Measurements were carried out using the image processing method with a Raspberry Pi camera and an optical liquid water sensor. The results of the measurements are displayed on the monitor screen with the VNC Viewer software. The measurement results using an optical liquid water level sensor are accurate with a relative error of 0% in each measurement, namely at 1 mm, 2 mm and 3 mm. For measurements using the image processing method, the average error generated is 2.3% at a height of 1 mm, 6.9% at a height of 2 mm, 3.3% at a height of 3 mm, 0.9% at a height of 4 mm and 0 .24% at 5 mm height.

High-precision fiber optic liquid level sensor based on fast Fourier amplitude demodulation in a specific range of spectrum

This study presents a fiber optic liquid level sensor (FOLLS) by acquiring information from the amplitude of spectral fast Fourier transform (FFT) in a specified narrow wavelength range. The sensing light path is simply formed by embedding a section of Panda-type polarization-maintaining fiber (PMF) into the sensing arm of a conventional Michelson interferometer (MI) structure. The output composite spectrum consists of two parts: the fine interference fringes due to MI optical path difference (OPD) and the envelope fringes stemming from the PMF’s birefringence. By applying liquid level variations on the sensing structure, shifts in envelope wavelength indicate a sensitivity of −0.193 nm/cm, and a liquid level resolution of 1 mm can be easily acquired. Furthermore, by demodulating the amplitude after spectral FFT in a specific narrow wavelength range, and intensity sensitivity of 1.906 dB/cm is achieved, leading to a greatly improved overall resolution of 0.03 mm in liquid level measurement. Besides, the sensing element is sealed and packaged by two sheets of silicone rubber, which can be thrown into liquid when in use, thus easing the sensor installation. Moreover, due to the proposed demodulation method, the sensor is insensitive to the light source power jitter, reference arm phase shift and optical spectral analyzer wavelength shift. Therefore, the merits of the proposed sensor include high precision, high stability, ease of installation, which are beneficial in pore water pressure and liquid level monitoring.

Hydrostatic Fiber Optic Liquid Level Sensor with position sensitive detector

This article presents the rationale and methodology for developing an intrinsically safe device, namely, a hydrostatic fiber optic sensor with a position-sensitive detector for monitoring the level of oil products in large-capacity tanks at oil depots and during pumping in a raw material warehouses. This device suitable for continuous monitoring of the liquid level, based on the measurement of a hydrostatic column of liquid with automatic offset of changes in the density of the liquid. Offset is carried out by means of a displacer (a fully submerged float), inside which a housing with a position-sensitive detector (PSD) is integrated. Theoretical validation of the bellows suspension usage for a displacer is given. During filling a container with a liquid whose level is measured, liquid bellows, the movement of which is recorded by an optical triangulation sensor using the reflected infrared ray incident on the bottom of the bellows. The principle of the triangulation sensor operation is based on the geometric properties of the triangles. The pulses of infrared radiation come through a fiber optic cable. In order to measure the movement of the surface (the bottom of the bellows) by measuring the movement of the reflected beam, a position-sensitive detector is used, which is located in a remote controller. In this device for the intrinsic safety problem solution, optical inputs of a fiber optic flat cable are located in the active zone of the sensor, which is connected to the optical inputs of a position-sensitive detector, operated on the principles of photoelectric effect. The light spot moving along the sensitive zone and converted by the detector into a one-dimensional signal proportional to the distance to the object. hydrostatically applies pressure over the entire effective area of the measuring

Optical liquid-level sensor based on a designed light guide plate

An optical liquid-level sensor based on a designed light guide plate (LGP) is proposed and experimentally demonstrated. Light transmits between the two surfaces of the LGP as in an optical waveguide. The front surface of the LGP is planar and contacts the liquid, and the back surface is designed with microstructures to uniform the light distribution by scattering. The uniform light intensity that escapes from the LGP abruptly decreases at the liquid level. A linear charge-coupled device (CCD) near the back surface is used to detect the liquid level by detecting the abrupt decrease in the light intensity. The feasibility of the proposed sensor is proved by a ray-tracing simulation and an experiment. The sensor shows high linearity and accuracy with a measurement error of 0.12 mm. The measurement range can be extended flexibly.

Optical fibre liquid sensor for cryogenic propellant mass measurement

The authors report a one-piece flexible liquid level optical fibre sensing probe in this Letter, which is meant to measure the liquid level inside the cryogenic propellant tanks of spacecraft and rockets. The ultra-lightweight sensing probe can be used in both aerospace vehicles and in any type of cryogenic fluid storage system. In contrast to current liquid gauging technologies such as Delta-P pressure sensor, capacitance probe, ultrasonic sensor, and silicon diode liquid level sensing probe, the fibre optic continuous liquid level sensor has unique advantages in terms of gauging accuracy, reliability, simplicity, and maintenance. The sensor uses one single optical fibre probe to measure the liquid level and the liquid distribution of cryogenic propellant. Every point of the sensing fibre is a ‘point sensor’ that is able to distinguish liquid and vapour. The physical location of each ‘point sensor’ can be determined with 1 mm spatial resolution or better. The optical fibre probe can be installed in a propellant tank with the same manner as currently used silicon diode liquid level sensing probe via only one single feed-through to connect to an optical signal interrogation unit located outside the tank. Experiments on measuring liquid nitrogen level are demonstrated.

Ultrahigh-sensitive multimode interference-based fiber optic liquid-level sensor realized using illuminating zero-order Bessel–Gauss beam

A proposal toward the enhancement in the sensitivity of a multimode interference-based fiber optic liquid-level sensor is explored analytically using a zero-order Bessel–Gauss (BG) beam as the input source. The sensor head consists of a suitable length of no-core fiber (NCF) sandwiched between two specialty high-order mode fibers. The coupling efficiency of various order modes inside the sensor structure is assessed using guided-mode propagation analysis and the performance of the proposed sensor has been benchmarked against the conventional sensor using a Gaussian beam. Furthermore, the study has been corroborated using a finite-difference beam propagation method in Lumerical’s Mode Solutions software to investigate the propagation of the zero-order BG beam inside the sensor structure. Based on the simulation outcomes, the proposed scheme yields a maximum absolute sensitivity of up to 3.551 dB / mm and a sensing resolution of 2.816 × 10 − 3 mm through the choice of an appropriate length of NCF at an operating wavelength of 1.55 μm. Owing to this superior sensing performance, the reported sensing technology expedites an avenue to devise a high-performance fiber optic-level sensor that finds profound implication in different physical, biological, and chemical sensing purposes.

Liquid Level Measurement Based on FBG-Embedded Diaphragms With Temperature Compensation

This paper proposes a fiber optic liquid level sensor system based on a silica fiber Bragg grating embedded into an epoxy resin diaphragm coupled to a temperature reference sensor, used to compensate the temperature cross-sensitivity for improving the liquid level measurement accuracy. The proposed system was tested in an industrial water tank with heating and recirculation. The results demonstrated a temperature cross-sensitivity reduction, enhancing the liquid level measurement thermal stability by a factor of nine, when compared with some single head sensor configurations reported in literature. Our system presents high linearity ( $R>0.999$ ), superior sensitivity (2.8 pm/mm), and much lower temperature related error (1.04 mm/°C), when compared with the other diaphragm-based sensors recently reported in the literature.

Non-contact optical Liquid Level Sensors

Information about characteristics of the optical liquid level sensor are present. Sensors are used to control of the light level limit fluid - water, kerosene, alcohol, solutions, etc. Intrinsically safe, reliable and easy to use. The operating principle of the level sensor is an optoelectronic infrared device.

Continuous Liquid-Level Sensor Based on a Long-Period Grating and Microwave Photonics Filtering Techniques

A fiber optic liquid-level sensor based on a long period grating (LPG) is proposed and experimentally validated. The principle of operation is based on a technique used to analyze microwave photonics filters. A 4-cm-long LPG cascaded with a high-reflectivity fiber Bragg grating is employed to achieve a continuous liquid-level sensor. The measurements have been performed using a modulator and a photo-detector with a modest bandwidth of less than 500 MHz, showing a sensitivity of −12.71 dB/cm and a standard deviation of 0.52 dB. One of the significant advantages of such sensing structure is that it is based on low-bandwidth radio frequency and off-the-shelf photonic components. In addition, the simple proposed scheme presents good repeatable performance and proves to be intrinsically robust against environmental changes, stable, and easy to reconfigure.

An optical liquid level sensor based on core-offset fusion splicing method using polarization-maintaining fiber

A simple liquid level sensor using a small piece of hydrofluoric acid (HF) etched polarization maintaining fiber (PMF), with SMF-PMF-SMF fiber structure based on Mach- Zehnder interference (MZI) mechanism is proposed. The core-offset fusion splicing method induced cladding modes interfere with the core mode. Moreover, the changing liquid level would influence the optical path difference of the MZI since the effective refractive indices of the air and the liquid is different. Both the variations of the wavelength shifts and power intensity attenuation corresponding to the liquid level can be obtained with a sensitivity of 0.4956nm/mm and 0.2204dB/mm, respectively.

Polymer Optical Fiber Continuous Liquid Level Sensor for Dynamic Measurement

The effect of cladding mode frustrated total internal reflection (CMFTIR) in macrobend polymer optical fiber is first used to achieve continuous liquid-level dynamic sensing. However, the difficulty is that the CMFTIR sensing signal is so weak as to be drowned into background noises. To solve this problem, the sensors with the parallel (twisted) helical macrobend coupling structure (PHMBCS and THMBCS) are designed to obtain dark-filed coupling signal which is found to be excellent on signal-to-noise ratio. The experiment shows that the sensor can dynamically measure the continuous change of water level, and the curve tracks are related to the speed of water flow. The result offers the possibility to calculate the real-time speeds of the level change. The measurement range of PHMBCS is 70 mm, and THMBCS reaches 350 mm. Better linearity is realized using THMBCS. The average level resolutions of the sensors with two structures are both less than 0.3 mm, and the measurement results show a very good consistency. The sensor, which has a good prospect of application, meets the needs of dynamic measurement of liquid level, especially under complicated electromagnetic and flammable environment.

Optical fiber liquid level sensor based on macro-bending coupling

A novel optical liquid level sensor based on macro-bending coupling of fiber is proposed. Two plastic fibers are twisted and twined on a polyamide stick to construct a liquid level sensor. The results show that the output light power has a linear change with the variation of the liquid level. The higher sensitivity is acquired for the higher refractive index liquid and the smaller radius of the macro-bending of fibers. At the same time, the temperature effect to the sensor has also been researched and discussed.

Light Path Model of Fiber Optic Liquid Level Sensor Considering Residual Liquid Film on the Wall

The working principle of the refractive-type fiber optic liquid level sensor is analyzed in detail based on the light refraction principle. The optic path models are developed in consideration of common simplification and the residual liquid film on the glass tube wall. The calculating formulae for the model are derived, constraint conditions are obtained, influencing factors are discussed, and the scopes and skills of application are analyzed through instance simulations. The research results are useful in directing the correct usage of the fiber optic liquid level sensor, especially in special cases, such as those involving viscous liquid in the glass tube monitoring.

Fiber Optic Liquid Level Sensor Based on Integration of Lever Principle and Optical Interferometry

We present a fiber-optic liquid level sensor that is conducted by a combination of optical interferometry and lever principle. The sensing unit is a Mach-Zehnder interferometer (MZI), which is formed by sandwiching a piece of photonic crystal fiber (PCF) between two single-mode fibers (SMFs). The measuring equipment is composed of a rotatable lever and a fixed link. The rotatable lever includes two different length arms, i.e., L1 and L2. Both ends of the MZI are glued on the tip of the L2 arm and the fixed link using ethoxyline, respectively. A hanging stick, which is dipped into a liquid tank, is directly mounted on the other end of the rotatable lever. The buoyancy will increase as the stick depth of immersion into the liquid increases. The tension the MZI subjected will increase according to the proportion of L1/L2 on account of the lever principle. The sensitivity of the sensor could be regulated with different ratios of lever arms. In our experiment, a maximum sensitivity of 111.27 pm/mm was obtained with a 1 : 7.8 ratio of two lever arms L1/L2. The demonstrated liquid level sensor has the advantages of simple structure, easy fabrication, low cost, and high sensitivity.

An optical liquid level sensor based on polarization-maintaining fiber modal interferometer

A novel optical liquid level sensor based on polarization-maintaining fiber (PMF) modal interferometer with waist enlarge splicing is proposed. A length of 35mm PMF is spliced between two single-mode fibers (SMF) to construct an all-fiber modal interferometer. The results show that the transmission spectrum has a red shift with the increasing level of liquid, and the higher sensitivity is acquired for the higher refractive index liquid. The sensitivities for the liquids with indices of 1.335, 1.363 and 1.382 are 0.279nm/mm, 0.437nm/mm and 0.516nm/mm respectively. At the same time, the temperature effect of the sensor has been measured and discussed.

Liquid level sensor based on an excessively tilted fibre grating

We propose and demonstrate an optical liquid level sensor based on the surrounding medium refractive index (SRI) sensing using an excessively tilted fibre grating (ETFG). When the ETFG submerged in water, two sets of cladding modes are coupled, corresponding to air- and water-surrounded grating structures, respectively. The coupling strengths of the two sets of cladding modes evolve with the submerging length of the grating, providing a mechanism to measure the liquid level. Comparing with long-period fibre grating based liquid level sensor, the ETFG sensor has a much higher SRI responsivity for liquids with refractive index around 1.33 and a lower thermal cross sensitivity.

Comparative study of f iber optic liquid level sensors based on long-period f iber gratings with dif ferent doping concentrations

The performances of two liquid level sensors based on long-period fiber gratings are studied. The long-period gratings (LPGs) have similar characteristics (length and period), but are fabricated with two photosensitive B-Ge co-doped fibers with different dopant concentrations. We investigate the temperature sensitivities of LPGs and exploit their refractive index sensitivity to implement liquid level measurement. By controlling fiber parameters, such as the dopant concentrations, the measurement sensitivity of a LPG-based fiber optic liquid level sensor can be improved.

Implementation and Characterization of Liquid-Level Sensor Based on a Long-Period Fiber Grating Mach–Zehnder Interferometer

An optical liquid-level sensor (LLS) based on a long-period fiber grating (LPG) interferometer is proposed and experimentally demonstrated. Two identical 3-dB LPGs are fabricated to form an in-fiber Mach-Zehnder interferometer, and the fiber portion between two LPGs is exposed to the liquid as the sensing element. The sensitivity and measurement range of the sensors employing different orders of cladding modes are investigated both theoretically and experimentally. The experimental results show good linearity and large measurement range. One of the significant advantages of such a sensing structure is that the measurement level is not limited to the length of the LPG itself. Also, the measurement range and sensitivity of the proposed LLS can be readily tailored for a particular applications.

PMMA (polymethyl methacrylate) fiber optic probe as a noncontact liquid level sensor

AbstractThis article reports the principle of operation, design aspects, experimentation, and performance of a noncontact fiber optic liquid level sensor. The sensor is based on the phenomenon of reflective concept. The device consists of fiber optic transmitter, fiber optic probe, floating reflector, photodiode detector, and digital multimeter. The fiber optic probe consists of two 60‐cm‐long PMMA (polymethyl methacrylate) fibers of diameter 1 mm, numerical aperture 0.5, core refractive index 1.492, and cladding refractive index 1.402. The fiber optic sensor is a promising alternative to other well‐established methods for the measurement of liquid level due to its simplicity of design, high precision, long‐term stability, linearity, high degree of sensitivity, dynamic range, noncontact sensing, and low cost of the fabrication make it suitable for applications in precise level control in analytical and process chemistry, biochemistry, bioanalytics, and on‐line measurement or inspection of liquid level. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2114–2118, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25415

Optical fiber-based liquid level sensor

A liquid level sensor based on etched D-shaped silica optical fibers is presented. The optical transmission of the sensor depends on the liquid level. The sensor can be realized as a continuous level sensor with a high resolution and requires only one fiber and one optical source and detector. We have demonstrated a sensor with a resolution of ~1 mm. The sensor works for liquids with refractive indices greater than ~1.45. We show that the sensor response is the same for increasing and decreasing liquid levels.