Francesca Romana Parente

Unmasking of Olive Oil Adulteration Via a Multi-Sensor Platform

Methods for the chemical and sensorial evaluation of olive oil are frequently changed and tuned to oppose the increasingly sophisticated frauds. Although a plethora of promising alternatives has been developed, chromatographic techniques remain the more reliable yet, even at the expense of their related execution time and costs. In perspective of a continuous increment in the number of the analyses as a result of the global market, more rapid and effective methods to guarantee the safety of the olive oil trade are required. In this study, a novel artificial sensorial system, based on gas and liquid analysis, has been employed to deal with olive oil genuineness and authenticity issues. Despite these sensors having been widely used in the field of food science, the innovative electronic interface of the device is able to provide a higher reproducibility and sensitivity of the analysis. The multi-parametric platform demonstrated the capability to evaluate the organoleptic properties of extra-virgin olive oils as well as to highlight the presence of adulterants at blending concentrations usually not detectable through other methods.

Full range analog Wheatstone bridge-based automatic circuit for differential capacitance sensor evaluation

Summary In this paper, an integrable novel fully analog Wheatstone bridge-based interface for differential capacitance estimation is presented. Its working principle takes advantage of the modified De-Sauty AC bridge configuration being employed only by two capacitors and two resistors. A feedback loop controls one of the resistors (e.g. a voltage-controlled resistor), to obtain an evaluation of the differential capacitance variation on a full range, thanks to a general but very simple formula that considers both the ‘auto-balancing’ and the bridge ‘out-of-equilibrium’ ranges. The proposed interface shows a satisfactory accuracy, being the percentage relative error within 0.45% for the experimental results. Copyright

A standard CMOS technology fully-analog differential capacitance sensor front-end

In this paper we present an analog electronic interface, developed in an integrated standard CMOS technology, for differential capacitive sensors. In particular, the two cases of hyperbolic and linear capacitive behavior have been considered. The capacitive evaluation can be done by the design and characterization of a suitable electronic circuit which determines the measurand variations through the reading of a voltage. This approach has shown high accuracy as well as other solutions reported in the literature where the capacitances are typically converted into a frequency. The front-end has been designed in a standard CMOS technology (AMS 0.35 um) to work at dual supply voltages (1.65 V each), so to be suitable for low-cost portable applications. Spice simulations on the designed integrated solution and experimental results using a discrete-component prototype have shown a reduced absolute percentage error (lower than 1% and 3.5 %, respectively), if compared to theoretical expressions. Sensitivity and resolution on a practical case study of the sensor/interface system are also given, showing very satisfactory values.

Analog current-mode interfaces for differential capacitance sensing

In this work, we present two analog current-mode interfaces performing differential sensor capacitance measurements through a voltage reading. The AC peak-to-peak output voltage is proportional to the measurand x that is directly related to the differential capacitance variation. The first interface is able to read the sensor change through a current-to-voltage conversion, while the second one employs an input voltage source. Both of the solutions utilize commercial second generation current conveyors (CCII) as active blocks, in particular AD844. The proposed electronic circuits have been designed and simulated through PSPICE software. Theoretical analysis, simulated and experimental results have been analyzed: the developed read-out circuits have shown a good accuracy, being the maximum percentage error between simulation and theory lower than 0.09% for the first solution, while in the second interface the maximum relative percentage error, with respect to theory, is lower than 0.2% in the simulated case and than 3.2% for the measurements, respectively. Considering a distance between electrodes variation measurand sensitivity (S) and resolution (res) values are also satisfactory for each operating point: for the first solution we obtained S=8.54 V/μm and res=674 pm (capacitance resolution value is 89.85 fF, that is -79 dB), while for the second one S=8.13 V/μm and res=814 pm (capacitance resolution value is 108.5 fF, that is -77 dB). The signal peak-to-peak voltage value detection has been implemented by using a NI DAQ device and a Virtual Instrumentation Suite (NI ELVIS).

A standard CMOS bridge-based analog interface for differential capacitive sensors

This work describes an analog electronic interface, based on a modified De Sauty AC bridge, performing a differential capacitive sensor estimation. A suitable feedback loop tunes a Voltage Controlled Resistor to balance the bridge. The electronic circuit has been designed in a standard integrated CMOS technology (AMS 0.35μm) with a low supply voltage (±1.5 V) and a reduced power consumption (lower than 4mW). PSpice simulation results show a very good agreement with theoretical expectations. The output voltage accuracy shows a 0.03V maximum absolute error for a range of ±50% of sensor variations from its baseline value. Very small baseline values are allowed (tens of μF).

An Electronic System for the Contactless Reading of ECG Signals

The aim of this work is the development of a contactless capacitive sensory system for the detection of (Electrocardiographic) ECG-like signals. The acquisition approach is based on a capacitive coupling with the patient body performed by electrodes integrated in a front-end circuit. The proposed system is able to detect changes in the electric charge related to the heart activity. Due to the target signal weakness and to the presence of other undesired signals, suitable amplification stages and analogue filters are required. Simulated results allowed us to evaluate the effectiveness of the approach, whereas experimental measurements, recorded without contact to the skin, have validated the practical effectiveness of the proposed architecture. The system operates with a supply voltage of ±9 V with an overall power consumption of about 10 mW. The analogue output of the electronic interface is connected to an ATmega328 microcontroller implementing the A/D conversion and the data acquisition. The collected data can be displayed on any multimedia support for real-time tracking applications.

A sensorial platform for mozzarella cheese characterization and authentication

Mozzarella cheese is one of the most counterfeited dairy product worldwide, with implications concerning either economical and health issues. In the context of food quality monitoring and authentication, a non-destructive multi-sensorial analytic approach is proposed. A minimally invasive evaluation of the mechanical properties of the mozzarella cheese as well as of its preserving whey has been performed by means of a mechanical and a liquid sensor, respectively. Data fusion of both approaches allowed a good and easy discrimination between mozzarella cheese samples having different brand provenance and milk composition.

Design and Development of an Electronic Interface for Gas Detection and Exhaled Breath Analysis in Liquids

Among gas sensors, the ones measuring carbon dioxide and oxygen are crucial for many application fields: the monitoring of air quality, the control of food packaging processes, the study of biochemical mechanisms, and specific reactions related to many different studies in the biomedical context. Many of the sensors used for the measure of carbon dioxide (CO2) and oxygen (O2) are based on electrochemical, optical, and conductometric working principles, which allow to cover the very different ranges of concentration which represent the target of each different field or specific application with good reproducibility and sensitivity. This paper presents a voltammetric sensor showing an innovative approach for the measure of gas and vapors by the interaction of a screen-printed electrode system with the liquid solution, where the gases are conveyed. The design and realization of this sensor system are reported. Calibration tests with CO2 and O2 have given acceptable reproducibility and sensitivity. Besides, this paper shows that new results have been obtained by analyzing exhaled breath collected by control individuals.

A simplified architecture for differential capacitance sensors

This paper describes a simple approach to perform differential capacitance measurements by the design and characterization of a dedicated electronic circuit. Capacitance transducers provide information about changes in capacitance in response to a physical variation. They are used in many types of applications such as linear displacement sensors, pressure transducers and accelerometers. The operating principle of the interface circuit is discussed. The proposed electronic circuit is designed and simulated by PSPICE software. Theoretical analysis and simulated results are analyzed.

CCII-Based Voltage Amplifier Optimization for Reduced Relative Gain Error

This paper describes strategies to design voltage amplifiers, based on the second-generation current conveyors, CCIIs, with a relative gain error (RGE). The approach is independent from the internal architecture of the employed CCII and allows to reduce the RGE of the overall amplifier by taking into account the main CCII non-idealities. In particular, it describes how to evaluate the specific optimum resistive loads minimizing RGE, also proving that these values are independent from the CCII internal implementation and related only to the parasitic components at X and Z nodes as well as to the desired ideal voltage gain. In order to validate the proposed design methodology, the commercial component AD844 has been considered as the CCII. Both analytical relationships and experimental results confirm the calculation of an optimum load resistance which minimizes the RGE of the voltage amplifier and, simultaneously, that a more accurate voltage gain can be obtained if the nominal values of the CCII parasitic resistances are taken into account. The reported findings provide design rules to implement, also at transistor level in a standard CMOS technology, CCII-based voltage amplifiers with low relative gain errors, which are of special interest for sensor interfaces and measurement systems.