The multisine excitation is widely used in impedance measurements to retain the advantages of the sine wave, while reducing the measurement time. Adding up sine waves increases the amplitude of the excitation signal, but, for the linearity assumption to be valid, the overall amplitude of the signal needs to be kept low. Thus, the crest factor (CF) of the excitation signal must be minimized. A novel empirical method for the minimization of the CF is described in this paper. As in the case of other known methods, the computed CF may be guaranteed to be only a local minimum. However, a systematic variation of initial parameters, which is possible due to the sparing algorithm, ensures a CF value very close or equal to the global minimum. The results of CF minimization and comparison with the results from other sources are provided. The direct CF optimization results (set of optimal phases) are not well suited for practical implementation. The influence of phase accuracy on the CF is discussed, and an algorithm for the recalculation of initial phases to the rougher set is described. It is shown that previously obtained optimization results (minimal CF) can be highly preserved, even in the case of rough phase resolutions. The CF of the multisine also depends on the frequency distribution and amplitudes of its components. The CF of multisines with several frequency distributions are compared.

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This paper deals with finding the highly efficient multifrequency excitation waveforms for fast bioimpedance spectroscopy. However, the solutions described here could be useful also in other fields of impedance spectroscopy. Theoretically, the useful excitation power of optimized binary multifrequency signals (BMS) exceeds the power of comparable multisine waveforms. However, part of power of the BMS waveforms is spread between higher harmonics of the wanted frequency components. In practical use of voltage excitation, the higher harmonics complicate the signal processing and produce current spikes passing through the capacitive elements of the impedance to be measured. In the paper, we show that the excitation power of well-optimized multisine with decaying amplitudes comes close to the power of comparable binary waveform while reducing the problems caused by unwanted frequency components. This allows simpler signal processing. Besides, we also show that the overall efficiency of using of the multisine excitation in impedance measurement becomes even higher efficient than the BMS in practice, despite the fact that the power of binary waveforms is the highest.

In this paper, certain aspects of choosing excitation waveforms for fast identification of the complex electrical impedance over a wide frequency range are discussed. For this purpose, several chirp-like short-time excitation signals with near to minimal duration are proposed. The results of computer simulation and analysis are promising for implementing such kind of signals as the stimulating ones in the bioimpedance measurement.

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Impedance spectroscopy is a common approach in assessing passive electrical properties of biological matter. However, several problems appear in microfluidic devices in connection with the requirement for high sensitivity of signal acquisition from small volume sensors. The developed compact and inexpensive analyzer provides impedance spectroscopy measurement from three sensors, both connected in direct and differential modes. Measurement deficiencies are reduced with a novel design of sensors, measurement method, optimized electronics, signal processing, and mechanical design of the analyzer. Proposed solutions are targeted to the creation of reliable point-of-care (POC) diagnostic and monitoring appliances, including lab-on-a-chip type devices in the next steps of development. The test results show the good working ability of the developed analyzer; however, also limitations and problems that require attention and further improvement are appointed.

Multisine excitation is widely used in impedance measurements to retain the advantages of the sine wave, while reducing the measurement time. To keep the crest factor (CF) of the excitation signal low, the initial phases of the signal components must be optimized. This paper focuses in further optimization of multisine signal for improving the signal-to-noise ratio (SNR) of measurements, reducing the complexity of signal generation and minimizing a memory footprint of the FPGA based implementation.

This paper deals with using of simple but energy efficient binary multififrequency excitation waveforms for fast bioimpedance spectroscopy. Binary waveforms can not only be generated in a simple way, but also the amount of useful excitation energy in these exceeds the energy of comparable sine wave based signals. This type of signals allows also versatile adapting (matching) of the shapes of the spectra of the object and excitation signal.