| 1. |
- Olarte, Oscar, et al.
(författare)
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Fractional frequency domain identification of NaCl-glucose solutions at physiological levels
- 2014
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Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 50:1, s. 213-221
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Tidskriftsartikel (refereegranskat)abstract
- Electrical impedance spectroscopy (EIS) has been used to characterize different biological materials. This article exposes a methodology oriented to estimate glucose levels of a solution based on a rational fractional parametric model of the impedance data. The methodology is applied over saline-glucose solutions at five physiological glucose levels, using three sensors and five repetitions for each glucose concentration and employed sensor. The results suggest that changes in the glucose concentration produce significant changes in the impedance that should be reflected in the parametric model. The modeling procedure shows that the poles and zeros of an integer model presents a degree of correlation. However, the correlation is clearly explicit employing fractional models where the mean location of the complex zeros is highly related to the glucose content in the sample.
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| 2. |
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| 3. |
- Olarte, O., et al.
(författare)
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Glucose characterization based on electrochemical impedance spectroscopy
- 2014
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Ingår i: IEEE Instrumentation and Measurement Technology Conference. - 9781467363853 ; , s. 833-837
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Konferensbidrag (refereegranskat)abstract
- In this paper an equivalent circuit model is employed in the characterization of the impedance measurements of saline solutions at physiological glucose concentrations. The impedance data are obtained using a three electrodes cell configuration since it allows measuring the potential accurately in the working electrode independently from the counter electrode. As excitation signal an odd random phase multisine is employed which allows identifying the best linear approximation, the noise level and the non-linear distortions present in the system. The results show a significant change in the impedance as a function of the glucose at the interphase electrode-electrolyte as well as in the bulk solution. This is an important step towards the development of glucose measurement systems based in electrochemical impedance spectroscopy (EIS).
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| 4. |
- Olarte, Oscar, et al.
(författare)
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Influence of the type and position of the sensor on the precision of impedance glucose measurements
- 2013
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Ingår i: 2013 IEEE International Instrumentation and Measurement Technology Conference (I2MTC). - New York : IEEE conference proceedings. - 9781467346214 - 9781467346221 ; , s. 1750-1754
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Konferensbidrag (refereegranskat)abstract
- Electrochemistry Impedance Spectroscopy has been proposed as a promising technique for non-invasive glucose monitoring. Although it is possible to find related literature to in-vitro and in-vivo experiments, no clear information is available regarding the precision of the measurements. In this paper, we address the problem of the precision due to different samples of the same sensor type and different sensor positions. We will show that the precision of the measurements is high for different sensor positions (over 96 %) but can drop significantly when different sensors are used (around 90 %), even when these sensors belong to the same brand.
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| 5. |
- Olarte, Oscar, et al.
(författare)
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Measurement and characterization of glucose in NaCl aqueous solutions by electrochemical impedance spectroscopy
- 2014
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Ingår i: Biomedical Signal Processing and Control. - : Elsevier BV. - 1746-8094. ; 14:1, s. 9-18
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical impedance spectroscopy (EIS) allows measuring the properties of the system as a function of the frequency as well as distinguishing between processes that could be involved: resistance, reactance, relaxation times, amplitudes, etc. Although it is possible to find related literature to in vitro and in vivo experiments to estimate glucose concentration, no clear information regarding the condition and precision of the measurements are easily available. This article first address the problem of the condition and precision of the measurements, as well as the effect of the glucose over the impedance spectra at some physiological (normal and pathological) levels. The significance of the measurements and the glucose effect over the impedance are assessment regarding the noise level of the system, the experimental error and the effect of using different sensors. Once the data measurements are analyzed the problem of the glucose estimation is addressed. A rational parametric model in the Laplace domain is proposed to track the glucose concentration. The electrochemical spectrum is measured employing odd random phase multisine excitation signals. This type of signals provides short acquisition time, broadband measurements and allows identifying the best linear approximation of the impedance as well as estimating the level of noise and non-linearities present in the system. All the experiments were repeated five times employing three different sensors from the same brand in order to estimate the significance of the experimental error, the effects of the sensors and the effect of the glucose over the impedance.
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| 6. |
- Olarte, Oscar, et al.
(författare)
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Using the Best Linear Approximation as a First Step to a New Non-Invasive Glucose Measurement
- 2012
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Ingår i: 2012 IEEE International Instrumentation and Measurement Technology Conference (I2MTC). - 9781457717734 ; , s. 2747-2751
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Konferensbidrag (refereegranskat)abstract
- In this paper an approach to develop a non-invasive glucose measured system based on the best linear approximation (BLA) and electrical impedance spectroscopy (EIS) is presented. In order to test the advantages of the technique, three blood components at reference blood concentration are tested. In these solutions the level of glucose was varied from normal to pathological concentrations. The results show the ability of BLA-EIS to detect the glucose changes by combining the amplitude and phase behavior of the impedance.
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| 7. |
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| 8. |
- Amin, Shoaib, et al.
(författare)
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Characterization of concurrent dual-band Power Amplifiers using a dual two-tone excitation signal
- 2015
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - : IEEE Press. - 0018-9456 .- 1557-9662. ; :99
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Tidskriftsartikel (refereegranskat)abstract
- A method to characterize the memory effects in a nonlinear concurrent dual-band transmitter is presented. It is an extension of the conventional two tone test for power amplifiers to concurrent dual band transmitters. The output signal of a concurrent dual-band transmitter is affected not only by intermodulation products but also by cross-modulation products. In one frequency band, the transmitter is excited by a two tone signal which frequency separation is swept. In the second band the transmitter is concurrently excited by an other two tone signal with slightly wider frequency separation. The frequency difference of the two signals is fixed during the frequency sweep. The two tone test is made at different power levels. The upper and lower third-order inter- and cross-modulation products are measured. The asymmetry between the upper and lower third-order inter- and cross-modulation products are measures of the transmitter's memory effects. The measurement results show that the memory effects are more dominant in the third-order intermodulation products than in the cross modulation products. An error analysis and system calibration was performed and measurement results for two different devices are presented.
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| 9. |
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| 10. |
- Barbé, Kurt, et al.
(författare)
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A Simple Nonparametric Preprocessing Technique to Correct for Nonstationary Effects in Measured Data
- 2012
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; 61:8, s. 2085-2094
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Tidskriftsartikel (refereegranskat)abstract
- The general approach for modeling systems assumes that the measured signals are (weakly) stationary, i.e., the power spectrum is time invariant. However, the stationarity assumption is violated when: 1) transient effects due to experimental conditions are dominant; 2) data are missing due to, for instance, sensor failure; or 3) the amplitude of the excitation signals smoothly varies over time due to, for instance, actuator problems. Although different methods exist to deal with each of these nonstationary effects specifically, no unified approach is available. In this paper, a new and general technique is presented to handle nonstationary effects, based on processing overlapping subrecords of the measured data. The proposed method is a simple preprocessing step where the user does not need to specify which nonstationary effect is present, nor the time interval where the nonstationary effect appears. The merits of the proposed approach are demonstrated on an operational wireless system suffering from interrupted link effects.
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