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Design and Implementation of SOC-Based Noncontact-Type Level Sensing for Conductive and Nonconductive Liquids

Design and Implementation of SOC-Based Noncontact-Type Level Sensing for Conductive and... Hindawi Advances in Materials Science and Engineering Volume 2021, Article ID 7630008, 12 pages https://doi.org/10.1155/2021/7630008 Research Article Design and Implementation of SOC-Based Noncontact-Type Level Sensing for Conductive and Nonconductive Liquids 1 1 2 J. L. Mazher Iqbal , Munagapati Siva Kishore, Arulkumaran Ganeshan , and G. Narayan Department of Electronics & Communication Engineering, School of Electrical & Communication, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science and Technology, Chennai, India Department of Electrical and Computer Engineering, Bule Hora University, Bule Hora, Ethiopia School of Electronics Engineering, Vellore Institute of Technology (VIT), Vellore, India Correspondence should be addressed to J. L. Mazher Iqbal; mazheriq@gmail.com and Arulkumaran Ganeshan; drgarulkumaran@bhu.edu.et Received 1 August 2021; Revised 16 August 2021; Accepted 19 August 2021; Published 5 October 2021 Academic Editor: Samson Jerold Samuel Chelladurai Copyright © 2021 J. L. Mazher Iqbal et al. +is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In contrast to the existing electromechanical systems, the noncontact-type capacitive measurement allows for a chemically and mechanically isolated, continuous, and inherently wear-free measurement. Integration of the sensor directly into the container’s wall offers considerable savings potential because of miniaturization and installation efforts. +is paper presents the imple- mentation of noncontact (NC)-type level sensing techniques utilizing the Programmable System on Chip (PSoC). +e hardware system developed based on the PSoC microcontroller is interfaced with capacitive-based printed circuit board (PCB) strip. +e designer has the choice of placing the sensors directly on the container or close to it. +is sensor technology can measure both the conductive and nonconductive liquids with equal accuracy. measurement, fuel-level measurement, engine oil mea- 1.Introduction surement, and cooling water level. Capacitive sensor’s ad- Nowadays, all automotive vehicles are fitted with a fuel-level vantages are higher sensitivity, lower mechanical stress, sensor. It measures the quantity of fuel left in the fuel tank. A higher reliability, and lower impact on the temperature fuel-level sensor is present in the fuel tank for a prolonged coefficients. Several methods are available to convert the period and exposed to fuel, fuel additives, corrosive sulphur, capacitance into analog voltages. +e popular techniques methanol, and ethanol. So, manufactures in the automobile used in capacitance-to-analog voltage converters are tran- industry need novel solutions for the longevity of fuel-level simpedance amplifier and an alternating current (AC) sensors. +e novel solutions should also reduce cost, space, bridge with voltage amplifier. +e limitations of these and weight and enhance the reliability of fuel sensors. +e techniques are low sensitivity and nonidealities of the sensor. fuel-level sensor can sense numerous liquid in the auto- +e low sensitivity in the interfacing circuit is due to ig- mobile industry such as cooling water, windshield cleaning noring the minimum change in the capacitance. +e non- engine oil, and power steering fluid. +e noninductive, idealities are temperature, induced frequency, and switch capacitance-based sensor is capable of estimating the level of noise. +is paper discusses the current in the noncontact- conducting as well as nonconducting fluids. +e level sensor type level measuring technique using System on Chip (SoC)- checks the fluid level in tanks. Level sensors quantify the based approach. fluid level at straight and bent states of fuel tanks. Recently, +e paper [1] discusses a noncontact fluid level mea- capacitive sensors have been used in many applications such surement method. +e resources used in the level sensor as touch sensing, proximity detection systems, brake fluid were enameled copper winding wire, acrylic bar, acrylic 2 Advances in Materials Science and Engineering pipes, and acrylic sheet. In paper [2], noncontact capaci- computing the error of fluid oxygen level-to-capacitance tance-type level sensors for conductive fluids are discussed. translation. In paper [23], the authors designed and fabri- +e paper [3] discusses the capacitive-based level sensor cated a fluid level measurement structure created on a which is used in ingestion water circulation systems. +e beached tubular capacitive sensor for conductive fluids. +e aquatic level sensor has been intended by multilayer pipes structure is not capable to shield the potential of the ex- and is equivalent to a commercially existing ultrasound tensive computing choice and high linearity. +e paper [24] aquatic level sensor. +e limitation is that it is a contact discusses the features of a paired spiral capacitance sensor sensor. +e paper [4] discusses the water level computation for the quantity of the fluid theft in flat lubricant-aquatic using the capacitive sensor with the printed circuit board dual-stage drift. +e limitation of the paper is that it does not (PCB). +e paper [5] discusses the capacitive touch systems consider the edge protecting conductors to decrease the with styli consisting of the touch sensor, analog frontend current. +e paper [25] discusses a method established on a integrated circuit, and microcontroller unit. +e limitation is modest linear capacitor array, and it is capable of resolving the degradation of the signal to noise ratio as the touch differences of the solid fraction. +e paper [26] presents a modified version of a noncontact capacitance level trans- sensor is located far from the finger. +e paper [6] presents an extensive review of the various types of sensors used in ducer for a conducting liquid explained in paper [7]. +e automobiles. +e paper [7] discusses the multifunctional paper [27] discusses the interfacing of a capacitive sensor parallel-plate capacitor sensor with four electrodes. +e level with the common microcontroller Arduino. +e paper [28] of the fluid is determined by sensing the values of the ca- discusses the possibilities of using common off-the-shelf pacitance. Furthermore, the permittivity and angle of the ultrasonic sensors for fuel-level sensing applications. fluid container are also estimated. +e paper [8] presents a +e paper [29] presents a noninvasive portable ca- liquid-level sensor based on etched fiber Bragg grating pacitive transducer for measuring fuel level of portable (FBG). In this, an edge-emitting light emitting diode (LED) engines. Although the sensor itself is not in direct contact feeds aFBG which is partially in air and partially immersed in with the fuel, the measurement unit consists of three the liquid. +e difference in the absorption spectra is used to coated copper electrodes which are inside the fuel tank. +e paper [30] discusses the optical fiber sensor established measure the liquid level. +e paper [9] presents a liquid-level measurement on silica spout configuration. +e paper [31] discusses the system based on a remote grounded capacitive sensor. +e optical fiber sensor for an instantaneous measure of fluid sensor comes in direct contact with the liquid whose level is level and temperature. +e sensor is designed by incor- being measured, thus making it prone to degradation. +e porating a no-core fiber and fiber Bragg raucous. +e paper paper [10] discusses the development of a capacitive sensor [32] discusses the capacitive sensor with an array of for minute liquid droplet detection. It works on the principle electrodes resembling to comb structure for fluid level of a change in dielectric constant between the plates of a measurement. +e paper [33] discusses the Helmholtz parallel-plate capacitor driven by an AC voltage. However, resonance process to design a fluid level gauge using liquid the intended use of this sensor is in liquid dispensing sys- hydrogen. +e paper [34] discusses the fluid level mea- tems. +e paper [11] presents a measurement system that has surement structure founded on energetic pipe pressure been developed using a single-tube capacitive sensor to conventional for high-temperature corrosive molten salts. determine the fluid level in vehicular fuel tanks which ad- +e paper [35] discusses the fluid level structure based on dresses the effect of fuel sloshing due to vehicle acceleration. discrete wavelet packet multiresolution proportional in- In our earlier article [12–16], high-performance reconfig- tegral (PI) controller. urable architectures were proposed. +e architecture dis- In paper [36], the authors discuss the flexible liquid-level cussed does not discuss the concept of SoC computing. +e optical fiber sensing to measure the liquid level. In paper paper [17] discusses the development of a PCB-based ca- [37], the authors discuss the light guide plate-based optical pacitive pressure sensing system. +e paper [18] presents a liquid-level sensor. +e paper [38] discusses the develop- fiber optic liquid-level sensor based on a Mach–Zender ment of the capacitive fuel measurement sensor. +e sensor optical interferometer. A major disadvantage of this system comprises of two copper plates acting like a parallel-plate is that it works best at a temperature range of 20–40 C. capacitor. +e system detects a change in fluid level based on the change in capacitance. In paper [39], the authors +e paper [19] discusses the electrical model intended for noncontact capacitance-based liquid sensors to define designed an instrument for determining the liquid level. +e instrument uses a multisensory model comprising a ca- liquid-level dependence. In paper [20], the authors designed a noncontact uniform circular cylinder-based capacitance- pacitive level sensor, ultrasonic level sensor, and capacitance type level sensor for a conducting fluid made of insulating pressure sensor to measure the liquid. +e paper [40] dis- material. An improved linear operational amplifier with cusses a fuel-level measurement model based on a single- adjustable bridge sensitivity measures the variation in ca- tube cross-capacitance sensor. +e disadvantage is that it is pacitance due to variation in the liquid level. +e paper [21] an immersive-type sensor, making it prone to quicker discusses the signal conditioning circuit minimum parasitic degradation. From the above literature review, it is evident that the implemented methodologies are predominantly capacitance for translating capacitance variation into fre- quency. +e limitation of the transformer is that the circuit is contact-type sensing techniques. +e limitations are that the liquid is to be immersed in the tube and a separate structure not complementary metal-oxide-semiconductor (CMOS) compatible. +e paper [22] discusses the method of is needed to know the liquid level. Advances in Materials Science and Engineering 3 In this paper, we describe the development of a distant noise immunity is to broaden the gap between the sensor capacitive-type level sensor. +e proposed sensor is fabri- and the ground. cated using an easily available multilayer PCB. +e sensor comprises a PCB configured with two coplanar probes. +is 2.2. Mechanical Variations. Mechanical variations within paper focuses on the brake fluid level measurement in four- the system can take many forms to change the sensor’s C . wheelers. +e proposed methodology in this paper over- +ere are two types of mechanical variations. comes the limitation discussed in the literature. +e flex PCB (1) Motionless disparity is usually generated through structure is to be mounted on the container wall. +e ca- pacitive-type fluid level measurement using a capacitive developed tolerances in the sensor assembly, PCB, and sensor arrangement towards the fluid container. sensor is easy to assemble, costs less, more robust, high Static variations, if understood and controlled, are repeatability, high resolution, and easy to install. Using this compensated during manufacturing with the base- methodology lowers the development cost of the sensor and line calibration operation. related interfacing electronic circuits. +is paper is orga- nized as follows. Section 2 presents the proposed method- (2) Dynamic variation is caused during operation. +ese ology and design resources. +e capacitance modeling and changes often manifest themselves as changes to C analysis are presented in Section 3. Section 4 presents the by changing the sensor’s capacitor dimensions. design and implementation of capacitance liquid-level Unlike temperature changes, dynamic variation is sensing. Section 5 presents the results and discussion. Fi- difficult to compensate. It is the best to design the nally, Section 6 presents the conclusion. system to minimize dynamic-mechanical variation effects on the sensors. 2.Proposed Methodology +e most common mechanical variation encountered is a change in the distance between capacitor plates, where the +is section discusses the methodology and hardware- first plate is the sensor and the second plate is the liquid software design resources for noncontact-type level sensing surface. It is triggered through air-bubbles present in the and their feasibility. +e capacitor structural sensor is adhesive. +e adhesive attaches the sensors to the con- proposed in this paper. Fluid level is a significant parameter tainer—the air-bubbles propagate and shrink through air in the industrial evolutions. A noticeable substitute in the pressure. Another cause is when the sensors are not directly industrial automation is the capacitive level measurement in attached to the liquid container allowing a changing air gap relative to mechanical structures. Capacitive fluid level between the sensor substrate and the container wall. +ese sensors are conductive packs or dash pads placed on a effects are reduced by eliminating air-bubbles; hence, the nonconductive material such as plastic or glass or PCB. +e mechanical design is adequate to sustain precise sensor intrinsic capacitance of the PCB dash pads is the parasitic arrangement. capacitance (C ). Once the fluid moves towards the sensor, a small fluid capacitance (C ) is added to C . +is is illustrated in Figure 1. Liquid-level sensing implies calculating the 2.3. Temperature Effects. Temperature variations during increased capacitance while water exists near the sensor. maneuvers have a substantial effect on performance. +e Programmable System on Chip (PSoC) 4 CapSense Compensation for temperature deviation is addressed Element given in the PSoC Creator Integrated Development through augmented sensor designs. A small isolating air gap should exist between the fluid basin and the sensor substrate. Environment (IDE) processes the capacitance through in- troducing a current into the sensor through a current Digital to Analog Converter (IDAC). A timer measures how long it 2.4. Capacitive Level Measurement. Even though capacitive takes the IDAC to charge the sensor’s voltage to a reference level sensing is a familiar technique, it is not used in au- voltage using a comparator. tomotive applications because of its sensitivity to the con- ductivity of the fluid and variations in dielectric constant. Contemporary development in capacitive level sensing such 2.1. Parasitic Capacitance. +e parasitic capacitance (C ) is as smart capacitive organization with reparation of the side the undesirable capacitance present between chunks of an effects and emergent processor power in the sensors makes electronic circuit purely because they are located close to use in automobile applications. each other. +e CapSense Element processes the total ca- pacitance and addition of parasitic and fluid capacitance 2.5. Capacitive Sensor Section. +e capacitive sensor section (C � C + C ) restricted by dynamic range. +e bigger TOTAL L the C , the lesser the fluid slice of the entire signal. It reduces consists of the fixed capacitor on a typical PCB intended to the system sensitivity in the presence of liquid hence in- measure the fuel level. +e design arrangement of the ca- creases the total system accuracy. +e main components of pacitive sensors is distinct. +e inclination of the fluid is parasitic capacitance in CapSense designs are sensor ca- determined using differential capacitive measurement. PSoC pacitance and dash capacitance. +e sensor dimensions are 4200 is used as the target device to implement the non- increased by increasing the in-dash measurement and re- contact-type level sensing. +e PSoC-4 device with CapSense ducing the annular gap. However, it leads to more C value. circuitry (CY8CKIT-042) is interfaced with capacitive +e technique that decreases the C value and declines the sensors. It senses the deviation in the capacitance in the P 4 Advances in Materials Science and Engineering Container Wall Liquid Ground Ground C C P Sensor P Container Wall PCB Liquid Ground Ground C C Sensor P P PCB (a) (b) Figure 1: (a) Capacitive level sensor. (b) Extra capacitance once fluid approaches the sensor. container. It also calculates the liquid level based on the GND capacitance variations of the sensors in the CapSense block Oscillator Modulator Clock shown in Figure 2. Figure 3 shows the system-level diagram. R SW1 GND +– 3.Capacitance Modeling Vref SW2 HI-Z Sigma-Delta +is section describes the implementation of a five-segment C C Input Converter P F isensor capacitance linear slider. +e linear capacitance sensor de- Raw Count Output bugs data and positions the slider on a PC using the Cap- Sense embedded tuner Graphical User Interface (GUI) via CMOD I2C communication. +e CapSense tuner provides a quick and easy method for monitoring and updating capacitance Figure 2: CapSense block diagram. linear slider parameters. sensor also increment the current through the resistor. +e 3.1. CapSense Component. +is section demonstrates the CapSense block adjusts by controlling the modulation and functionality of the CapSense component. Figure 4 shows frequency of the oscillator which results in an increase in the PSoC top design and pins mapping diagram of the voltage between the resistors. capacitive linear slider. +e capacitive linear slider uses CapSense and EZI2C Slave modules. 4. Design and Implementation +is section presents the design and demonstration of ca- 3.2. Firmware. After building and installing the project in pacitance liquid-level sensing. +e linear sensor capacitance CY8CKIT-042, launch the Tuner Graphical User Interface debugs and positions the data and liquid using the inbuilt (GUI) and then right-click the CapSense Component and CapSense tuner on a PC as a friendly GUI via universal select launch tuner in the menu to configure it as an analog asynchronous receiver-transmitter (UART) communica- channel. +e analog channel gets the raw count of the ca- tion. +is CapSense tuner GUI gives the observer a pre- pacitance shown in Figure 5. Figures 6 and 7 show the dictive method for validating and calibration of capacitance firmware flowchart and the circuit diagram of CapSense parameters. block. +e proposed work uses the smart sense (Full Auto- Tune) tuning method to implement a linear slider. +e 4.1. Design. +e design spark schematic tool draws the EZI2C slave is used to display the sensor information and logical design and drives the PCB design. However, the PCB slider touch position statistics on a PC using the CapSense drawing tool is used without importing the layout schematic. tuner in the PSoC Creator IDE via Inter-Integrated Circuit +e PCB design produces the productional data and the final (I2C). assembled PCB. Design Spark generates the Geber files, and +e current through the resistor is measured and con- generated Geber files are directly sent to the manufacturer. verted to equivalent voltage using a current to voltage From this Gerber data, the EMS providers can produce the rectifier. +e capacitance of the sensor is incremented when final physical PCBs. A capacitive sensor built utilizing dis- the touch is recognized. +e increments in capacitance of the tinctive materials relies upon the prerequisite and Advances in Materials Science and Engineering 5 CapSense Liquid SWD UART MCU USB Sensors programmer or Debugger Intergated Development Development Hardware Interfacing connector Environment Figure 3: System-level diagram. Slider Interface I2C Interface EZI2C CapSense CapSense EZI2C On Board To PC USB-I2C Bridge Slave Figure 4: Top design and pin mapping. overlay. +e well-known strategy for sensor development is the etching of copper pads and FR4 PCB material. 4.2. Overlay Parameters. In a capacitance sensor configu- ration, overlay material is put over the sensor pad to shield it from the anticipation of direct finger contact and envi- ronment parameters. +e geometry of a capacitive esti- Figure 5: Analog channel configuration for CapSense. mating framework is profoundly complex than a coplanar parallel-plate capacitor. In the parallel-plate capacitance application. Capacitive sensor development incorporates a model, C is corresponding to ε . Further, high dielectric F r conductive surface which detects that the user touch is steady will result in high sensitivity. Because of the lower associated with the pin of the capacitive controller utilizing a dielectric constant of air, any bubbles/air gaps between the conductive follow or connection. It clarifies that an entire sensor cushion and overlay ought to be maintained at a development plan is underneath a nonconductive overlay strategic distance for better resolution. Dielectric constants material. +e user has access to approach the top side of the of usually utilized overlay materials for PCB are recorded in Connectors Connectors Container 6 Advances in Materials Science and Engineering Table 1: Dielectric constants of insulation materials. Start Material Dielectric constant Air 1.0 Formica 4.6–4.9 Initialize EZI2C and Glass (standard) 7.6–8.0 CapSense Components Glass (ceramic) 6.0 Pet film (mylar) 3.2 Polycarbonate (lexan) 2.9–3.0 Scan all Widgets Acrylic (plexiglass) 2.8 ABS 2.4–4.1 Wood table 1.2–2.5 Gypsum 2.5–6.0 Is CapSense Busy? overlay. Sensitivity is reciprocally dependent on the thick- ness of overlay material, as illustrated in Figure 8. Overlay materials should have reasonable mechanical contact to the PCB sensor. +is can be accomplished utilizing a 3M type Process all widgets nonconductive sort adhesive film. +is increases the sen- sitivity of the system by taking out any air gaps in the middle of the overlay and the sensor pads. Is any Widget active? 4.3. Sensor PCB Design. +e sensor terminals have been planned with geometrical parameters chosen for a sufficient sensitivity. +e PCB is structured utilizing Design Spark. Figures 9 and 10 show the sensor PCB and sensor pattern, respectively. +e PCB is manufactured by an external Perform Tasks based on the vendor, with the parameters shown in Table 2. Figure 11 scan result shows the fabricated PCB. +e designed sensor is further fabricated and tested by using the high precision LCR meter. +e designed PCBs have a parasitic capacitance of ∼37 pF Run the Tuner (with overlay). +e capacitance can change depending on the medium and can go up to ∼200 pF considering the human hand as a reference to determine the max effective capaci- Start next Scan tance. Each PCB exhibits different capacitance based on their properties and overlay materials. So, it is required to de- termine the capacitance thresholds of the designed sensor. Figure 6: Firmware flowchart. Initially, it is measured using a high-resolution LCR meter. +e maximum capacitance is determined by having a human hand placed proximity to the sensor. +e measurement desk appears in Figure 12. +e designed sensor is interfaced to Cypress PSoC4 dev kit using the interfacing card. +e interfaced card has the impedance matching resistors of 560 ohms in each sensor lines. +e connector pin layout is made that can be easy to interface. Figure 13 shows the connector layout of the sensor. +e designed sensor is interfaced with Cypress PSoC 4 dev kit using the interfacing card. +e connector pin layout is made that can be easy to interface. 4.4. Measurement and Calibration. +e noncontact-type Figure 7: Circuit diagram of CapSense block. fluid level system arrangement consists of four segments. Figure 14 shows the diagram of a fluid level system. +e Table 1. Materials with dielectric steady somewhere in the device under-test (DUT) consists of a sensor, interfacing range of 2.0 and 8.0 are appropriate for capacitive detecting card, and PSoC 4. +e sensor input is directly integrated into applications. +e conductive material cannot be fit as an the container’s wall that offers a considerable savings po- overlay substrate due to its impedance. Consequently, we tential in terms of miniaturization and installation efforts. should not utilize paints that contain metal particles in the +e output is taken from PSoC 4. +e PSoC 4 is a Advances in Materials Science and Engineering 7 overlay thickness Figure 11: Fabricated PCB. Figure 8: Sensitivity vs. overlay thickness. Figure 9: Sensor PCB. Figure 12: Capacitance measurement by the LCR meter. Sensor Pad TX0_R 1 2 RX11 1 2 3 4 RX10 3 4 RX9 5 6 RX8 5 6 RX7 7 8 RX0 7 8 RX12 9 10 RX1 Ground Pad 9 10 RX2 11 12 RX6 11 12 RX4 13 14 RX3 13 14 RX5 15 16 15 16 Shielding layer Connector Pin Figure 13: Connector layout of sensor. Figure 10: Sensor pattern. development board, which utilizes a berg stick connector on another small interfacing board. +e estimation results perused at various levels of the Department of Trans- Table 2: Dielectric constants of insulation materials. portation (DOT4) type brake liquid segment from the base: PCB material FR4 zero levels with the base unfilled, 10 mm (similar tallness of +ickness 0.4 mm the reflected light (RL) sensor), 15 mm, and 20 mm. +e Type of pouring Copper dimension is estimated at most extreme 70 mm. Dimensions 100∗ 50 mm Connector type Berg stick 5. Result and Discussion programmable embedded system on chip, integrating cus- +e oscillator block provides the reference frequency for tom analog and digital peripheral functions, memory, and an capacitance detection. Figures 16 and 17 show the tuner Arm Cortex-M0 microcontroller on a single chip. Figure 15 widget view and tuner graph, respectively. A simulation is demonstrates the usage procedure and estimation. +e carried out to sense the capacitance ranging from 10pF to 50 personal computer (PC) is associated with the PSoC de- pF in the step size of 10 pF. Figure 18 shows the oscillator velopment board, PSoC creator 4.1, and Tera Term Terminal. frequency. Figures 19–21 show the CapSense-simulation. As +e PC with the PSoC 4 microcontroller (PSoC 4200M) dev the frequency varies with capacitance, the current across the platform uses the PSoC debugger connected to USB inter- sense resistor also varies. Figure 19 shows the current sense- face. +e test code is transferred to the microcontroller unit capacitance variation from 10 pF to 50 pF. +e sensed (MCU) by the PSoC Creator 4.1. +e information from the current is fed to the sigma-delta converter of PSoC. +e MCU is displayed in Tera Term window at serial commu- behavior of capacitance vs. current is analyzed imple- nication (COM2) port. +e sensor is placed on a noncon- menting a hardware rectifier and filter. It will rectify the ductive surface in association with the PSoC 4200M frequency output of the current sense to the direct current sensitivity 8 Advances in Materials Science and Engineering USB UART-RX PC Capacitance in. Psoc Interface PSoc 4200M Sensor Creator Card 4.1 Tera UART-TX term USB DUT Figure 14: Measurement diagram for the fluid level system. Figure 15: Device under-test-measurement setup. Figure 16: Tuner widget view. Figure 17: Tuner graph view. (DC) component. Figure 20 shows the output voltage after Term Terminal. +e PSoC development board measures the rectification of the concerned current. +is voltage values difference in capacitance between the two sensor pads as raw can be directly fed to any microcontroller using analog-to- counts. +e change in parasitic capacitance of the sensor is digital converters (ADCs) of higher resolution. Figure 21 avoided through proper shielding employed on the sensor. shows the rectification based on the peak voltage. Figure 22 shows the linearity of the sensor. +e measured +e PSoC 4 development board is configured for ca- capacitance values are read directly from the PSoC 4 board pacitance measurement. +e measured capacitance values by using Tera Term terminal. +e level capacitance is in- are read directly from the PSoC 4 board by using the Tera creased with the increase in the fluid level from bottom of the Advances in Materials Science and Engineering 9 V [n004] V0 90 99 108 117 126 135 144 153 162 171 180 189 μs Figure 18: Oscillator frequency output-100 kHz. V [n008] μA 0 –60 –120 –180 –240 –300 152 156 160 164 168 172 176 180 184 188 192 μs Figure 19: Current sense-capacitance varied from 10 pF to 50 pF. V [n010] 2.3 2.2 2.1 2.0 1.9 1.8 V 1.7 1.6 1.5 1.4 1.3 1.2 1.1 153 156 159 162 165 168 171 174 177 180 183 μs Figure 20: Current to rectified voltage output. tank. +e prominent change in parasitic capacitance of the is a low cost measurement method and can be deployed with sensor is eliminated by having proper shielding employed on different types of liquids. +e model is used for both con- the sensor. +e solution for reducing the temperature effects ductive and nonconductive liquid-level measurement. +e on the capacitance is attained by designing the sensor based model may be used in several applications because of its on Flexi PCB and maintains minimum connection length as structure strategy and process approach. +e applications possible. Level sensors are spearheaded in checking the fluid are proximity detection, touch buttons, irrigation, bio- level in tanks and are utilized in numerous applications. +e medical area, pharmaceutical industry, and automation development model of a distant capacitive-type level sensor application. +e proposed capacitive sort sensor is 10 Advances in Materials Science and Engineering V [n010] V [n008] I [R1] 3.0 300 2.4 240 1.8 180 1.2 120 0.6 60 V 0.0 0 μA –0.6 –60 –1.2 –120 –1.8 –180 –2.4 –240 –3.0 –300 153 156 158 162 165 168 171 174 177 180 183 μs Figure 21: Rectification based on the peak voltage. Capacitance Liquid level Observed in (mm) percentage (%) Figure 22: Sensor linearity. Table 3: Measurements at various temperatures. Fluid level (brake fluid) Temperature in degree Observed (mm) @40 mm Observed (mm) @50 mm Observed (mm) @60 mm Observed (mm) @70 mm 0 0 27.8 27.8 13.9 5 13.7 41.7 55.6 55.6 10 27.8 48.6 62.5 62.5 20 34.7 48.6 62.5 76.4 22.81 34.7 48.6 62.5 76.4 30 34.7 48.6 62.5 76.4 manufactured utilizing generally accessible multilayer PCB. sensor pads and a ground pad in between and to take the In this manner, the generation cost and the related inter- resultant capacitance difference. So, the sensor ability is facing electronic circuits are nearly less. verified through the temperature tests performed (0 C to 60 C—limitation in temperature due to the development board thresholds), and the results are shown in Table 3. 5.1. Temperature Tests. One of the main complexities for Figure 23 shows the temperature and fluid level. 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Design and Implementation of SOC-Based Noncontact-Type Level Sensing for Conductive and Nonconductive Liquids

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Copyright © 2021 J. L. Mazher Iqbal et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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1687-8442
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10.1155/2021/7630008
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Hindawi Advances in Materials Science and Engineering Volume 2021, Article ID 7630008, 12 pages https://doi.org/10.1155/2021/7630008 Research Article Design and Implementation of SOC-Based Noncontact-Type Level Sensing for Conductive and Nonconductive Liquids 1 1 2 J. L. Mazher Iqbal , Munagapati Siva Kishore, Arulkumaran Ganeshan , and G. Narayan Department of Electronics & Communication Engineering, School of Electrical & Communication, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science and Technology, Chennai, India Department of Electrical and Computer Engineering, Bule Hora University, Bule Hora, Ethiopia School of Electronics Engineering, Vellore Institute of Technology (VIT), Vellore, India Correspondence should be addressed to J. L. Mazher Iqbal; mazheriq@gmail.com and Arulkumaran Ganeshan; drgarulkumaran@bhu.edu.et Received 1 August 2021; Revised 16 August 2021; Accepted 19 August 2021; Published 5 October 2021 Academic Editor: Samson Jerold Samuel Chelladurai Copyright © 2021 J. L. Mazher Iqbal et al. +is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In contrast to the existing electromechanical systems, the noncontact-type capacitive measurement allows for a chemically and mechanically isolated, continuous, and inherently wear-free measurement. Integration of the sensor directly into the container’s wall offers considerable savings potential because of miniaturization and installation efforts. +is paper presents the imple- mentation of noncontact (NC)-type level sensing techniques utilizing the Programmable System on Chip (PSoC). +e hardware system developed based on the PSoC microcontroller is interfaced with capacitive-based printed circuit board (PCB) strip. +e designer has the choice of placing the sensors directly on the container or close to it. +is sensor technology can measure both the conductive and nonconductive liquids with equal accuracy. measurement, fuel-level measurement, engine oil mea- 1.Introduction surement, and cooling water level. Capacitive sensor’s ad- Nowadays, all automotive vehicles are fitted with a fuel-level vantages are higher sensitivity, lower mechanical stress, sensor. It measures the quantity of fuel left in the fuel tank. A higher reliability, and lower impact on the temperature fuel-level sensor is present in the fuel tank for a prolonged coefficients. Several methods are available to convert the period and exposed to fuel, fuel additives, corrosive sulphur, capacitance into analog voltages. +e popular techniques methanol, and ethanol. So, manufactures in the automobile used in capacitance-to-analog voltage converters are tran- industry need novel solutions for the longevity of fuel-level simpedance amplifier and an alternating current (AC) sensors. +e novel solutions should also reduce cost, space, bridge with voltage amplifier. +e limitations of these and weight and enhance the reliability of fuel sensors. +e techniques are low sensitivity and nonidealities of the sensor. fuel-level sensor can sense numerous liquid in the auto- +e low sensitivity in the interfacing circuit is due to ig- mobile industry such as cooling water, windshield cleaning noring the minimum change in the capacitance. +e non- engine oil, and power steering fluid. +e noninductive, idealities are temperature, induced frequency, and switch capacitance-based sensor is capable of estimating the level of noise. +is paper discusses the current in the noncontact- conducting as well as nonconducting fluids. +e level sensor type level measuring technique using System on Chip (SoC)- checks the fluid level in tanks. Level sensors quantify the based approach. fluid level at straight and bent states of fuel tanks. Recently, +e paper [1] discusses a noncontact fluid level mea- capacitive sensors have been used in many applications such surement method. +e resources used in the level sensor as touch sensing, proximity detection systems, brake fluid were enameled copper winding wire, acrylic bar, acrylic 2 Advances in Materials Science and Engineering pipes, and acrylic sheet. In paper [2], noncontact capaci- computing the error of fluid oxygen level-to-capacitance tance-type level sensors for conductive fluids are discussed. translation. In paper [23], the authors designed and fabri- +e paper [3] discusses the capacitive-based level sensor cated a fluid level measurement structure created on a which is used in ingestion water circulation systems. +e beached tubular capacitive sensor for conductive fluids. +e aquatic level sensor has been intended by multilayer pipes structure is not capable to shield the potential of the ex- and is equivalent to a commercially existing ultrasound tensive computing choice and high linearity. +e paper [24] aquatic level sensor. +e limitation is that it is a contact discusses the features of a paired spiral capacitance sensor sensor. +e paper [4] discusses the water level computation for the quantity of the fluid theft in flat lubricant-aquatic using the capacitive sensor with the printed circuit board dual-stage drift. +e limitation of the paper is that it does not (PCB). +e paper [5] discusses the capacitive touch systems consider the edge protecting conductors to decrease the with styli consisting of the touch sensor, analog frontend current. +e paper [25] discusses a method established on a integrated circuit, and microcontroller unit. +e limitation is modest linear capacitor array, and it is capable of resolving the degradation of the signal to noise ratio as the touch differences of the solid fraction. +e paper [26] presents a modified version of a noncontact capacitance level trans- sensor is located far from the finger. +e paper [6] presents an extensive review of the various types of sensors used in ducer for a conducting liquid explained in paper [7]. +e automobiles. +e paper [7] discusses the multifunctional paper [27] discusses the interfacing of a capacitive sensor parallel-plate capacitor sensor with four electrodes. +e level with the common microcontroller Arduino. +e paper [28] of the fluid is determined by sensing the values of the ca- discusses the possibilities of using common off-the-shelf pacitance. Furthermore, the permittivity and angle of the ultrasonic sensors for fuel-level sensing applications. fluid container are also estimated. +e paper [8] presents a +e paper [29] presents a noninvasive portable ca- liquid-level sensor based on etched fiber Bragg grating pacitive transducer for measuring fuel level of portable (FBG). In this, an edge-emitting light emitting diode (LED) engines. Although the sensor itself is not in direct contact feeds aFBG which is partially in air and partially immersed in with the fuel, the measurement unit consists of three the liquid. +e difference in the absorption spectra is used to coated copper electrodes which are inside the fuel tank. +e paper [30] discusses the optical fiber sensor established measure the liquid level. +e paper [9] presents a liquid-level measurement on silica spout configuration. +e paper [31] discusses the system based on a remote grounded capacitive sensor. +e optical fiber sensor for an instantaneous measure of fluid sensor comes in direct contact with the liquid whose level is level and temperature. +e sensor is designed by incor- being measured, thus making it prone to degradation. +e porating a no-core fiber and fiber Bragg raucous. +e paper paper [10] discusses the development of a capacitive sensor [32] discusses the capacitive sensor with an array of for minute liquid droplet detection. It works on the principle electrodes resembling to comb structure for fluid level of a change in dielectric constant between the plates of a measurement. +e paper [33] discusses the Helmholtz parallel-plate capacitor driven by an AC voltage. However, resonance process to design a fluid level gauge using liquid the intended use of this sensor is in liquid dispensing sys- hydrogen. +e paper [34] discusses the fluid level mea- tems. +e paper [11] presents a measurement system that has surement structure founded on energetic pipe pressure been developed using a single-tube capacitive sensor to conventional for high-temperature corrosive molten salts. determine the fluid level in vehicular fuel tanks which ad- +e paper [35] discusses the fluid level structure based on dresses the effect of fuel sloshing due to vehicle acceleration. discrete wavelet packet multiresolution proportional in- In our earlier article [12–16], high-performance reconfig- tegral (PI) controller. urable architectures were proposed. +e architecture dis- In paper [36], the authors discuss the flexible liquid-level cussed does not discuss the concept of SoC computing. +e optical fiber sensing to measure the liquid level. In paper paper [17] discusses the development of a PCB-based ca- [37], the authors discuss the light guide plate-based optical pacitive pressure sensing system. +e paper [18] presents a liquid-level sensor. +e paper [38] discusses the develop- fiber optic liquid-level sensor based on a Mach–Zender ment of the capacitive fuel measurement sensor. +e sensor optical interferometer. A major disadvantage of this system comprises of two copper plates acting like a parallel-plate is that it works best at a temperature range of 20–40 C. capacitor. +e system detects a change in fluid level based on the change in capacitance. In paper [39], the authors +e paper [19] discusses the electrical model intended for noncontact capacitance-based liquid sensors to define designed an instrument for determining the liquid level. +e instrument uses a multisensory model comprising a ca- liquid-level dependence. In paper [20], the authors designed a noncontact uniform circular cylinder-based capacitance- pacitive level sensor, ultrasonic level sensor, and capacitance type level sensor for a conducting fluid made of insulating pressure sensor to measure the liquid. +e paper [40] dis- material. An improved linear operational amplifier with cusses a fuel-level measurement model based on a single- adjustable bridge sensitivity measures the variation in ca- tube cross-capacitance sensor. +e disadvantage is that it is pacitance due to variation in the liquid level. +e paper [21] an immersive-type sensor, making it prone to quicker discusses the signal conditioning circuit minimum parasitic degradation. From the above literature review, it is evident that the implemented methodologies are predominantly capacitance for translating capacitance variation into fre- quency. +e limitation of the transformer is that the circuit is contact-type sensing techniques. +e limitations are that the liquid is to be immersed in the tube and a separate structure not complementary metal-oxide-semiconductor (CMOS) compatible. +e paper [22] discusses the method of is needed to know the liquid level. Advances in Materials Science and Engineering 3 In this paper, we describe the development of a distant noise immunity is to broaden the gap between the sensor capacitive-type level sensor. +e proposed sensor is fabri- and the ground. cated using an easily available multilayer PCB. +e sensor comprises a PCB configured with two coplanar probes. +is 2.2. Mechanical Variations. Mechanical variations within paper focuses on the brake fluid level measurement in four- the system can take many forms to change the sensor’s C . wheelers. +e proposed methodology in this paper over- +ere are two types of mechanical variations. comes the limitation discussed in the literature. +e flex PCB (1) Motionless disparity is usually generated through structure is to be mounted on the container wall. +e ca- pacitive-type fluid level measurement using a capacitive developed tolerances in the sensor assembly, PCB, and sensor arrangement towards the fluid container. sensor is easy to assemble, costs less, more robust, high Static variations, if understood and controlled, are repeatability, high resolution, and easy to install. Using this compensated during manufacturing with the base- methodology lowers the development cost of the sensor and line calibration operation. related interfacing electronic circuits. +is paper is orga- nized as follows. Section 2 presents the proposed method- (2) Dynamic variation is caused during operation. +ese ology and design resources. +e capacitance modeling and changes often manifest themselves as changes to C analysis are presented in Section 3. Section 4 presents the by changing the sensor’s capacitor dimensions. design and implementation of capacitance liquid-level Unlike temperature changes, dynamic variation is sensing. Section 5 presents the results and discussion. Fi- difficult to compensate. It is the best to design the nally, Section 6 presents the conclusion. system to minimize dynamic-mechanical variation effects on the sensors. 2.Proposed Methodology +e most common mechanical variation encountered is a change in the distance between capacitor plates, where the +is section discusses the methodology and hardware- first plate is the sensor and the second plate is the liquid software design resources for noncontact-type level sensing surface. It is triggered through air-bubbles present in the and their feasibility. +e capacitor structural sensor is adhesive. +e adhesive attaches the sensors to the con- proposed in this paper. Fluid level is a significant parameter tainer—the air-bubbles propagate and shrink through air in the industrial evolutions. A noticeable substitute in the pressure. Another cause is when the sensors are not directly industrial automation is the capacitive level measurement in attached to the liquid container allowing a changing air gap relative to mechanical structures. Capacitive fluid level between the sensor substrate and the container wall. +ese sensors are conductive packs or dash pads placed on a effects are reduced by eliminating air-bubbles; hence, the nonconductive material such as plastic or glass or PCB. +e mechanical design is adequate to sustain precise sensor intrinsic capacitance of the PCB dash pads is the parasitic arrangement. capacitance (C ). Once the fluid moves towards the sensor, a small fluid capacitance (C ) is added to C . +is is illustrated in Figure 1. Liquid-level sensing implies calculating the 2.3. Temperature Effects. Temperature variations during increased capacitance while water exists near the sensor. maneuvers have a substantial effect on performance. +e Programmable System on Chip (PSoC) 4 CapSense Compensation for temperature deviation is addressed Element given in the PSoC Creator Integrated Development through augmented sensor designs. A small isolating air gap should exist between the fluid basin and the sensor substrate. Environment (IDE) processes the capacitance through in- troducing a current into the sensor through a current Digital to Analog Converter (IDAC). A timer measures how long it 2.4. Capacitive Level Measurement. Even though capacitive takes the IDAC to charge the sensor’s voltage to a reference level sensing is a familiar technique, it is not used in au- voltage using a comparator. tomotive applications because of its sensitivity to the con- ductivity of the fluid and variations in dielectric constant. Contemporary development in capacitive level sensing such 2.1. Parasitic Capacitance. +e parasitic capacitance (C ) is as smart capacitive organization with reparation of the side the undesirable capacitance present between chunks of an effects and emergent processor power in the sensors makes electronic circuit purely because they are located close to use in automobile applications. each other. +e CapSense Element processes the total ca- pacitance and addition of parasitic and fluid capacitance 2.5. Capacitive Sensor Section. +e capacitive sensor section (C � C + C ) restricted by dynamic range. +e bigger TOTAL L the C , the lesser the fluid slice of the entire signal. It reduces consists of the fixed capacitor on a typical PCB intended to the system sensitivity in the presence of liquid hence in- measure the fuel level. +e design arrangement of the ca- creases the total system accuracy. +e main components of pacitive sensors is distinct. +e inclination of the fluid is parasitic capacitance in CapSense designs are sensor ca- determined using differential capacitive measurement. PSoC pacitance and dash capacitance. +e sensor dimensions are 4200 is used as the target device to implement the non- increased by increasing the in-dash measurement and re- contact-type level sensing. +e PSoC-4 device with CapSense ducing the annular gap. However, it leads to more C value. circuitry (CY8CKIT-042) is interfaced with capacitive +e technique that decreases the C value and declines the sensors. It senses the deviation in the capacitance in the P 4 Advances in Materials Science and Engineering Container Wall Liquid Ground Ground C C P Sensor P Container Wall PCB Liquid Ground Ground C C Sensor P P PCB (a) (b) Figure 1: (a) Capacitive level sensor. (b) Extra capacitance once fluid approaches the sensor. container. It also calculates the liquid level based on the GND capacitance variations of the sensors in the CapSense block Oscillator Modulator Clock shown in Figure 2. Figure 3 shows the system-level diagram. R SW1 GND +– 3.Capacitance Modeling Vref SW2 HI-Z Sigma-Delta +is section describes the implementation of a five-segment C C Input Converter P F isensor capacitance linear slider. +e linear capacitance sensor de- Raw Count Output bugs data and positions the slider on a PC using the Cap- Sense embedded tuner Graphical User Interface (GUI) via CMOD I2C communication. +e CapSense tuner provides a quick and easy method for monitoring and updating capacitance Figure 2: CapSense block diagram. linear slider parameters. sensor also increment the current through the resistor. +e 3.1. CapSense Component. +is section demonstrates the CapSense block adjusts by controlling the modulation and functionality of the CapSense component. Figure 4 shows frequency of the oscillator which results in an increase in the PSoC top design and pins mapping diagram of the voltage between the resistors. capacitive linear slider. +e capacitive linear slider uses CapSense and EZI2C Slave modules. 4. Design and Implementation +is section presents the design and demonstration of ca- 3.2. Firmware. After building and installing the project in pacitance liquid-level sensing. +e linear sensor capacitance CY8CKIT-042, launch the Tuner Graphical User Interface debugs and positions the data and liquid using the inbuilt (GUI) and then right-click the CapSense Component and CapSense tuner on a PC as a friendly GUI via universal select launch tuner in the menu to configure it as an analog asynchronous receiver-transmitter (UART) communica- channel. +e analog channel gets the raw count of the ca- tion. +is CapSense tuner GUI gives the observer a pre- pacitance shown in Figure 5. Figures 6 and 7 show the dictive method for validating and calibration of capacitance firmware flowchart and the circuit diagram of CapSense parameters. block. +e proposed work uses the smart sense (Full Auto- Tune) tuning method to implement a linear slider. +e 4.1. Design. +e design spark schematic tool draws the EZI2C slave is used to display the sensor information and logical design and drives the PCB design. However, the PCB slider touch position statistics on a PC using the CapSense drawing tool is used without importing the layout schematic. tuner in the PSoC Creator IDE via Inter-Integrated Circuit +e PCB design produces the productional data and the final (I2C). assembled PCB. Design Spark generates the Geber files, and +e current through the resistor is measured and con- generated Geber files are directly sent to the manufacturer. verted to equivalent voltage using a current to voltage From this Gerber data, the EMS providers can produce the rectifier. +e capacitance of the sensor is incremented when final physical PCBs. A capacitive sensor built utilizing dis- the touch is recognized. +e increments in capacitance of the tinctive materials relies upon the prerequisite and Advances in Materials Science and Engineering 5 CapSense Liquid SWD UART MCU USB Sensors programmer or Debugger Intergated Development Development Hardware Interfacing connector Environment Figure 3: System-level diagram. Slider Interface I2C Interface EZI2C CapSense CapSense EZI2C On Board To PC USB-I2C Bridge Slave Figure 4: Top design and pin mapping. overlay. +e well-known strategy for sensor development is the etching of copper pads and FR4 PCB material. 4.2. Overlay Parameters. In a capacitance sensor configu- ration, overlay material is put over the sensor pad to shield it from the anticipation of direct finger contact and envi- ronment parameters. +e geometry of a capacitive esti- Figure 5: Analog channel configuration for CapSense. mating framework is profoundly complex than a coplanar parallel-plate capacitor. In the parallel-plate capacitance application. Capacitive sensor development incorporates a model, C is corresponding to ε . Further, high dielectric F r conductive surface which detects that the user touch is steady will result in high sensitivity. Because of the lower associated with the pin of the capacitive controller utilizing a dielectric constant of air, any bubbles/air gaps between the conductive follow or connection. It clarifies that an entire sensor cushion and overlay ought to be maintained at a development plan is underneath a nonconductive overlay strategic distance for better resolution. Dielectric constants material. +e user has access to approach the top side of the of usually utilized overlay materials for PCB are recorded in Connectors Connectors Container 6 Advances in Materials Science and Engineering Table 1: Dielectric constants of insulation materials. Start Material Dielectric constant Air 1.0 Formica 4.6–4.9 Initialize EZI2C and Glass (standard) 7.6–8.0 CapSense Components Glass (ceramic) 6.0 Pet film (mylar) 3.2 Polycarbonate (lexan) 2.9–3.0 Scan all Widgets Acrylic (plexiglass) 2.8 ABS 2.4–4.1 Wood table 1.2–2.5 Gypsum 2.5–6.0 Is CapSense Busy? overlay. Sensitivity is reciprocally dependent on the thick- ness of overlay material, as illustrated in Figure 8. Overlay materials should have reasonable mechanical contact to the PCB sensor. +is can be accomplished utilizing a 3M type Process all widgets nonconductive sort adhesive film. +is increases the sen- sitivity of the system by taking out any air gaps in the middle of the overlay and the sensor pads. Is any Widget active? 4.3. Sensor PCB Design. +e sensor terminals have been planned with geometrical parameters chosen for a sufficient sensitivity. +e PCB is structured utilizing Design Spark. Figures 9 and 10 show the sensor PCB and sensor pattern, respectively. +e PCB is manufactured by an external Perform Tasks based on the vendor, with the parameters shown in Table 2. Figure 11 scan result shows the fabricated PCB. +e designed sensor is further fabricated and tested by using the high precision LCR meter. +e designed PCBs have a parasitic capacitance of ∼37 pF Run the Tuner (with overlay). +e capacitance can change depending on the medium and can go up to ∼200 pF considering the human hand as a reference to determine the max effective capaci- Start next Scan tance. Each PCB exhibits different capacitance based on their properties and overlay materials. So, it is required to de- termine the capacitance thresholds of the designed sensor. Figure 6: Firmware flowchart. Initially, it is measured using a high-resolution LCR meter. +e maximum capacitance is determined by having a human hand placed proximity to the sensor. +e measurement desk appears in Figure 12. +e designed sensor is interfaced to Cypress PSoC4 dev kit using the interfacing card. +e interfaced card has the impedance matching resistors of 560 ohms in each sensor lines. +e connector pin layout is made that can be easy to interface. Figure 13 shows the connector layout of the sensor. +e designed sensor is interfaced with Cypress PSoC 4 dev kit using the interfacing card. +e connector pin layout is made that can be easy to interface. 4.4. Measurement and Calibration. +e noncontact-type Figure 7: Circuit diagram of CapSense block. fluid level system arrangement consists of four segments. Figure 14 shows the diagram of a fluid level system. +e Table 1. Materials with dielectric steady somewhere in the device under-test (DUT) consists of a sensor, interfacing range of 2.0 and 8.0 are appropriate for capacitive detecting card, and PSoC 4. +e sensor input is directly integrated into applications. +e conductive material cannot be fit as an the container’s wall that offers a considerable savings po- overlay substrate due to its impedance. Consequently, we tential in terms of miniaturization and installation efforts. should not utilize paints that contain metal particles in the +e output is taken from PSoC 4. +e PSoC 4 is a Advances in Materials Science and Engineering 7 overlay thickness Figure 11: Fabricated PCB. Figure 8: Sensitivity vs. overlay thickness. Figure 9: Sensor PCB. Figure 12: Capacitance measurement by the LCR meter. Sensor Pad TX0_R 1 2 RX11 1 2 3 4 RX10 3 4 RX9 5 6 RX8 5 6 RX7 7 8 RX0 7 8 RX12 9 10 RX1 Ground Pad 9 10 RX2 11 12 RX6 11 12 RX4 13 14 RX3 13 14 RX5 15 16 15 16 Shielding layer Connector Pin Figure 13: Connector layout of sensor. Figure 10: Sensor pattern. development board, which utilizes a berg stick connector on another small interfacing board. +e estimation results perused at various levels of the Department of Trans- Table 2: Dielectric constants of insulation materials. portation (DOT4) type brake liquid segment from the base: PCB material FR4 zero levels with the base unfilled, 10 mm (similar tallness of +ickness 0.4 mm the reflected light (RL) sensor), 15 mm, and 20 mm. +e Type of pouring Copper dimension is estimated at most extreme 70 mm. Dimensions 100∗ 50 mm Connector type Berg stick 5. Result and Discussion programmable embedded system on chip, integrating cus- +e oscillator block provides the reference frequency for tom analog and digital peripheral functions, memory, and an capacitance detection. Figures 16 and 17 show the tuner Arm Cortex-M0 microcontroller on a single chip. Figure 15 widget view and tuner graph, respectively. A simulation is demonstrates the usage procedure and estimation. +e carried out to sense the capacitance ranging from 10pF to 50 personal computer (PC) is associated with the PSoC de- pF in the step size of 10 pF. Figure 18 shows the oscillator velopment board, PSoC creator 4.1, and Tera Term Terminal. frequency. Figures 19–21 show the CapSense-simulation. As +e PC with the PSoC 4 microcontroller (PSoC 4200M) dev the frequency varies with capacitance, the current across the platform uses the PSoC debugger connected to USB inter- sense resistor also varies. Figure 19 shows the current sense- face. +e test code is transferred to the microcontroller unit capacitance variation from 10 pF to 50 pF. +e sensed (MCU) by the PSoC Creator 4.1. +e information from the current is fed to the sigma-delta converter of PSoC. +e MCU is displayed in Tera Term window at serial commu- behavior of capacitance vs. current is analyzed imple- nication (COM2) port. +e sensor is placed on a noncon- menting a hardware rectifier and filter. It will rectify the ductive surface in association with the PSoC 4200M frequency output of the current sense to the direct current sensitivity 8 Advances in Materials Science and Engineering USB UART-RX PC Capacitance in. Psoc Interface PSoc 4200M Sensor Creator Card 4.1 Tera UART-TX term USB DUT Figure 14: Measurement diagram for the fluid level system. Figure 15: Device under-test-measurement setup. Figure 16: Tuner widget view. Figure 17: Tuner graph view. (DC) component. Figure 20 shows the output voltage after Term Terminal. +e PSoC development board measures the rectification of the concerned current. +is voltage values difference in capacitance between the two sensor pads as raw can be directly fed to any microcontroller using analog-to- counts. +e change in parasitic capacitance of the sensor is digital converters (ADCs) of higher resolution. Figure 21 avoided through proper shielding employed on the sensor. shows the rectification based on the peak voltage. Figure 22 shows the linearity of the sensor. +e measured +e PSoC 4 development board is configured for ca- capacitance values are read directly from the PSoC 4 board pacitance measurement. +e measured capacitance values by using Tera Term terminal. +e level capacitance is in- are read directly from the PSoC 4 board by using the Tera creased with the increase in the fluid level from bottom of the Advances in Materials Science and Engineering 9 V [n004] V0 90 99 108 117 126 135 144 153 162 171 180 189 μs Figure 18: Oscillator frequency output-100 kHz. V [n008] μA 0 –60 –120 –180 –240 –300 152 156 160 164 168 172 176 180 184 188 192 μs Figure 19: Current sense-capacitance varied from 10 pF to 50 pF. V [n010] 2.3 2.2 2.1 2.0 1.9 1.8 V 1.7 1.6 1.5 1.4 1.3 1.2 1.1 153 156 159 162 165 168 171 174 177 180 183 μs Figure 20: Current to rectified voltage output. tank. +e prominent change in parasitic capacitance of the is a low cost measurement method and can be deployed with sensor is eliminated by having proper shielding employed on different types of liquids. +e model is used for both con- the sensor. +e solution for reducing the temperature effects ductive and nonconductive liquid-level measurement. +e on the capacitance is attained by designing the sensor based model may be used in several applications because of its on Flexi PCB and maintains minimum connection length as structure strategy and process approach. +e applications possible. Level sensors are spearheaded in checking the fluid are proximity detection, touch buttons, irrigation, bio- level in tanks and are utilized in numerous applications. +e medical area, pharmaceutical industry, and automation development model of a distant capacitive-type level sensor application. +e proposed capacitive sort sensor is 10 Advances in Materials Science and Engineering V [n010] V [n008] I [R1] 3.0 300 2.4 240 1.8 180 1.2 120 0.6 60 V 0.0 0 μA –0.6 –60 –1.2 –120 –1.8 –180 –2.4 –240 –3.0 –300 153 156 158 162 165 168 171 174 177 180 183 μs Figure 21: Rectification based on the peak voltage. Capacitance Liquid level Observed in (mm) percentage (%) Figure 22: Sensor linearity. Table 3: Measurements at various temperatures. Fluid level (brake fluid) Temperature in degree Observed (mm) @40 mm Observed (mm) @50 mm Observed (mm) @60 mm Observed (mm) @70 mm 0 0 27.8 27.8 13.9 5 13.7 41.7 55.6 55.6 10 27.8 48.6 62.5 62.5 20 34.7 48.6 62.5 76.4 22.81 34.7 48.6 62.5 76.4 30 34.7 48.6 62.5 76.4 manufactured utilizing generally accessible multilayer PCB. sensor pads and a ground pad in between and to take the In this manner, the generation cost and the related inter- resultant capacitance difference. So, the sensor ability is facing electronic circuits are nearly less. verified through the temperature tests performed (0 C to 60 C—limitation in temperature due to the development board thresholds), and the results are shown in Table 3. 5.1. Temperature Tests. One of the main complexities for Figure 23 shows the temperature and fluid level. 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Advances in Materials Science and EngineeringHindawi Publishing Corporation

Published: Oct 5, 2021

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