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Nowadays, wearable wireless devices represent an exciting challenge both for controlling one's lifestyle and for specific applications like telemedicine and at-home healthcare monitoring. Many low-cost sensors and sensor systems are currently on the market, but only a limited number of them are validated and certified for clinical applications. This paper presents preliminary results of the accuracy assessment of an electrocardiography (ECG) device for cardiovascular disease monitoring that will be applied by the patients for self-checking. In particular, the analog front end integrated circuit MAX30001 is proposed and tested, while the principal features of MAX30001 evaluation board software were described, as well as three cardiac pathologies which require in-depth and continuous ECG monitoring. An accuracy setup was realized to evaluate the acquisition fidelity; it is based on a high-quality waveform generator that imposes to the MAX30001 two different periodic signals: a sine and a sinc with the frequency of 1 Hz to 10 Hz with a 5 Hz step. The accuracy evaluation shows how the integrated circuit provides a normalized root mean square error in the chosen frequency range, lower than 0.01 and lower than 0.20, respectively, for the sine and sinc waveform. Moreover, it presents for sinc signal a peak detection rate of 80%.

In this work, the evaluation of moisture content in historic wooden objects starting from permittivity measurements is investigated. For this purpose, a WR430 waveguide with a 1.7-2.6 GHz range was used to estimate the complex permittivity correlated to different moisture levels. Experimental tests were carried out on poplar (Populus nigra L.), a wood typically used in central Italy in the thirteenth-sixteenth centuries as a painting support. For the considered measurement system, experimental results and calibration curves are reported.

In this work, the dielectric permittivity of four kinds of wood (Fir, Poplar, Oak, and Beech Tree), used in Italian Artworks and structures, was characterized at different humidity levels. Measurements were carried out using three different probes connected to a bench vector network analyzer: a standard WR90 X-band waveguide, a WR430 waveguide, and an open-ended coaxial probe. In particular, we investigated the dispersion model for the four wood species, showing how a log-fit model of the open-ended data presents a determination coefficient R2 > 0.990 in the 1–12 GHz frequency range. This result has proven helpful to fill the frequency gap between the measurements obtained at different water contents with the two waveguide probes showing an R2 > 0.93. Furthermore, correlating the log-fit vertical shift with the water content, it was possible to find a calibration curve with a linear characteristic. These experimental results will be helpful for on-site non-invasive water monitoring of wooden artworks or structures. Moreover, the final results show how the open-ended coaxial probe, with a measurement deviation lower than 7% from the waveguide measurements, may be used directly as a non-invasive sensor for on-site measurements.

Dielectric permittivity-based measurement techniques are establishing themselves as attractive solutions for assessing moisture content of historic masonry materials. The relative simplicity of the measurement principle and the inherent adaptability to diverse operating conditions are two of the most notable features of these techniques. In spite of these specific advantages, however, there are still some aspects that hinder the widespread use of permittivity-based moisture content measurement systems, and make their standardization difficult. In particular, the density of the sample under test may affect the estimation of permittivity, thus possibly leading to inaccurate moisture content measurements. As a result, the measurement system should be re-calibrated even when the same type of material is being investigated (e.g., two samples of the same type of stone, but extracted from different quarries).To circumvent this problem and to fully exploit the potential of permittivity-based moisture content measurements, in this work, a strategy for compensating for the effect of density is addressed. In order to verify the suitability of this strategy, moisture content measurements were carried out on samples of two type of stones typical of historic masonry, namely gentile stone and red-clay brick.