Erica Silva Pinto

Bio: Erica Silva Pinto is an academic researcher from Universidade Federal de Ouro Preto. The author has contributed to research in topics: Capacitive sensing & Signal. The author has an hindex of 3, co-authored 6 publications receiving 14 citations.

Capacitive Impedance Measurement: Dual-frequency Approach.

Abstract: The most widely used technique for measuring capacitive impedances (or complex electrical permittivity) is to apply a frequency signal to the sensor and measure the amplitude and phase of the output signal. The technique, although efficient, involves high-speed circuits for phase measurement, especially when the medium under test has high conductivity. This paper presents a sensor to measure complex electrical permittivity based on an alternative approach to amplitude and phase measurement: The application of two distinct frequencies using a current-to-voltage converter circuit based in a transimpedance amplifier, and an 8-bit microcontroller. Since there is no need for phase measurement and the applied frequency is lower compared to the standard method, the circuit presents less complexity and cost than the traditional technique. The main advance presented in this work is the use of mathematical modeling of the frequency response of the circuit to make it possible for measuring the dielectric constant using a lower frequency than the higher cut-off frequency of the system, even when the medium under test has high conductivity (tested up to 1220 μS/cm). The proposed system caused a maximum error of 0.6% for the measurement of electrical conductivity and 2% for the relative dielectric constant, considering measurement ranges from 0 to 1220 μS/cm and from 1 to 80, respectively.

Sensor for measuring electrical parameters of soil based on auto-balancing bridge circuit

Abstract: The management of irrigation based on the monitoring of soil electrical parameters allows to rationalize the amount of resources used with the objective of developing a sustainable agriculture. In this sense, the present work presents a sensor of dielectric constant and conductivity of soil based on auto-balancing bridge circuit. The advances presented in this paper are related to the evaluation of the system in the field and to the development of a model for correcting the effect of ambient temperature on the measurement circuit of the sensor, through multiple linear regression. In this way, the reproducibility of the system was improved.

Bench System for Iron Ore Moisture Measurement

Abstract: Moisture content of materials is a widely used parameter for controlling several industrial processes. Especially in mining, this variable has fundamental importance for transporting and handling stages, which represent the most expensive part of ore treatment. This work presents the development of a bench system for measuring iron ore moisture in real time. The sensor consists of a pair of stainless steel electrodes and, differently to other systems for this purpose, it is based on a modern current-to-voltage method, which presents simple circuit, low-cost, high accuracy, high signal-to-noise ratio, fast response and immunity to stray capacitances.

A Novel Two Degrees of Freedom System for Measuring Iron Ore Water Content on a Conveyor Belt

Abstract: Water content or moisture of materials is a parameter widely used in the industry. In mining, it is an important variable to control in iron ore production. High moistures may cause instability of iron ore piles and may make transport by ship unfeasible. Therefore, this paper presents the development of a system for measuring iron ore moisture on a conveyor belt (laboratory-scale). The structure that supports the sensor has two degrees of freedom, which allow perpendicular and parallel movements. The parallel movement makes the relative velocity between the measurement cell and the ore almost zero. The vertical movement allows the sensor to be placed at different depths in the ore. These sets enable real-time and in situ measurements. The system uses the capacitive method to determine the dielectric constant of the iron ore located between the sensor electrodes and, consequently, the moisture. This system has a measuring range of 0 to 14% on a dry basis and presents an uncertainty up to 0.07 percentage points for a 2-standard-deviation confidence level. In the validation process, the absolute error was less than 0.34 percentage point in the mining interest range of 6 to 14%. The founded results achieve a significant advance in the development of real-time equipment for measuring ore moisture since there is no device capable of doing it with the necessary level of accuracy and precision. For mining, this kind of system represents a big step to take corrective and preventive decisions around iron ore moisture control.

sistema e método para medição de umidade de uma amostra de solo ou minério

Abstract: sistema e metodo para medicao de umidade de uma amostra de solo ou minerio a presente invencao esta relacionada a um sistema de bancada e/ou port til para medir, em tempo real, a umidade de minerio de ferro. a tecnica da presente invencao realiza a medicao de umidade de uma amostra de solo ou minerio por meio de variacoes de impedância de uma amostra com densidade aparente padronizada pelo proprio sistema, o sistema compreendendo meios para comprimir (2) a amostra ate que a mesma atinja uma densidade aparente predeterminada e meios para medir (12, 14) a umidade da amostra em um estado comprimido. a presente invencao ainda prove um metodo associado ao sistema acima mencionado.

Fully Printed Disposable IoT Soil Moisture Sensors for Precision Agriculture

Abstract: Digitization of industrial processes using new technologies (IoT—Internet of Things, IoE—Internet of Everything), including the agriculture industry, are globally gaining growing interest. The precise management of production inputs is essential for many agricultural companies because limited or expensive sources of water and nutrients could make sustainable production difficult. For these reasons, precise data from fields, plants, and greenhouses have become more important for decision making and for the proper dosage of water and nutrients. On the market are a variety of sensors for monitoring environmental parameters within a precise agricultural area. However, the high price, data storage/transfer functionality are limiting so cost-effective products capable to transfer data directly to farmers via wireless IoT networks are required. Within a given scope, low-price sensor elements with an appropriate level of sensor response are required. In the presented paper, we have developed fully printed sensor elements and a dedicated measuring/communicating unit for IoT monitoring of soil moisture. Various fabrication printing techniques and a variety of materials were used. From the performed study, it is obvious that fully printed sensor elements based on cheap and environmentally friendly carbon layers printed on the wood substrate can compete with conventionally made sensors based on copper.

Development and Characterization of Titanium Dioxide Ceramic Substrates with High Dielectric Permittivities

Abstract: Titanium dioxide substrates have been synthesized by means of solid-state reactions with sintering temperatures varying from 1150 °C up to 1350 °C. X-ray diffraction and scanning electron microscopy (SEM) where employed to investigate the crystal structure, grain size and porosity of the resulting samples. The obtained ceramics are tetragonal (rutile phase) with average grain sizes varying from 2.94 µm up to 5.81 µm. The average grain size of samples increases with increasing temperature, while the porosity decreases. The effect of microstructure on the dielectric properties has been also studied. The reduction of porosity of samples significantly improves the dielectric parameters (relative dielectric permittivity and loss tangent) in comparison to those of commercial substrates, indicating that the obtained ceramic substrates could be useful in the miniaturization of telecommunication devices.

A measurement method for lossy capacitive relative humidity sensors based on a direct sensor-to-microcontroller interface circuit

Abstract: A new time-domain measurement method for determining the capacitance and resistance values of lossy relative humidity capacitive sensors is presented. The method is based on a direct sensor-to-microcontroller interface for microcontrollers with internal analog comparators and timers. The interface circuit consists only of four reference resistors (two reference resistors if a microcontroller includes a voltage reference source), a given sensor and a microcontroller. A systematic error correction algorithm based on a correction dictionary and the M-multiple measurement approach are also proposed in the paper. Experimental investigations were carried out using a prototype device based on an 8-bit ATXmega32A4 microcontroller. The experimental research confirmed that the relative errors of measurement of capacitance introduced by the interface circuit are less than 0.71% (for capacitance values 100–286 pF), and the relative errors of measurement of resistance are less than 0.74% (for resistance values 1–10 MΩ).

Capacitive Impedance Measurement: Dual-frequency Approach.

Abstract: The most widely used technique for measuring capacitive impedances (or complex electrical permittivity) is to apply a frequency signal to the sensor and measure the amplitude and phase of the output signal. The technique, although efficient, involves high-speed circuits for phase measurement, especially when the medium under test has high conductivity. This paper presents a sensor to measure complex electrical permittivity based on an alternative approach to amplitude and phase measurement: The application of two distinct frequencies using a current-to-voltage converter circuit based in a transimpedance amplifier, and an 8-bit microcontroller. Since there is no need for phase measurement and the applied frequency is lower compared to the standard method, the circuit presents less complexity and cost than the traditional technique. The main advance presented in this work is the use of mathematical modeling of the frequency response of the circuit to make it possible for measuring the dielectric constant using a lower frequency than the higher cut-off frequency of the system, even when the medium under test has high conductivity (tested up to 1220 μS/cm). The proposed system caused a maximum error of 0.6% for the measurement of electrical conductivity and 2% for the relative dielectric constant, considering measurement ranges from 0 to 1220 μS/cm and from 1 to 80, respectively.

Comments to: A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils, Sensors, 15, 25546–25563

Abstract: The article comments on claims made by Rego et al. about the sensor they developed to determine soil water content and its salinity via the admittance measurement of electrodes embedded in the soil. Their sensor is not based on a self-balanced bridge, as stated, but on a more common technique relying on Ohm's law. A bridge is a zero method of measurement which can provide direct voltages proportional to soil permittivity and conductivity with a high resolution. Thanks to modern electronics the method can be adapted for fast and continuous monitoring in a remote site. Because of this confusion about the different measurement techniques among available admittance or capacitance sensors, we give a succinct review of them and indicate how they compare to the two techniques under discussion. We also question the ability of Rego et al.'s current sensor to determine both soil water content and salinity due first to instrument biases and then to the soil complexity as a dielectric medium. In particular, the choice of sensor frequencies is crucial in the two steps. In addition, the procedure to determine and account for temperature influences on readings is not presented clearly enough. It is important to distinguish between the effect resulting from electronics sensitivity, and those that are soil-specific. The comment does not invalidate the design of the sensor, but indicates points, especially parasitic contributions, which must be dealt with to avoid major errors.