Basics of broadband impedance spectroscopy measurements using periodic excitations

Abstract

Measuring the impedance frequency response of systems by means of frequency sweep electrical impedance spectroscopy (EIS) takes time. An alternative based on broadband signals enables the user to acquire simultaneous impedance response data collection. This is directly reflected in a short measuring time compared to the frequency sweep approach. As a result of this increase in the measuring speed, the accuracy of the impedance spectrum is compromised. The aim of this paper is to study how the choice of the broadband signal can contribute to mitigate this accuracy loss. A review of the major advantages and pitfalls of four different periodic broadband excitations suitable to be used in EIS applications is presented. Their influence on the instrumentation and impedance spectrum accuracy is analyzed. Additionally, the signal processing tools to objectively evaluate the quality of the impedance spectrum are described. In view of the experimental results reported, the impedance spectrum signal-to-noise ratio (SNRZ) obtained with multisine or discrete interval binary sequence signals is about 20–30 dB more accurate than maximum length binary sequence or chirp signals.

The Theory and Fundamentals of Bioimpedance Analysis in Clinical Status Monitoring and Diagnosis of Diseases

“…A logarithmic analysis carried out between 0.01 and 10 Hz with five frequencies needs 276 s to be completed, this includes the calculation time [75]. Sanchez et al [76] stated that real time processing, accuracy and the ability of data retrieval and throughput of a BIS system were the most important features to be applied in health monitoring systems, and Sanchez et al [77] introduced a local polynomial based method for impedance-frequency-response estimation.…”

“…Sanchez et al [76] stated that real time processing, accuracy and the ability of data retrieval and throughput of a BIS system were the most important features to be applied in health monitoring systems, and Sanchez et al [77] introduced a local polynomial based method for impedance-frequency-response estimation. Comparison studies between four different multi-sine periodic broadband excitations broadband for EIS measurements in term of accuracy and speed in frequency and time domain concluded that multi-sine and discrete interval binary sequences (DIBS) enhance SNRZ and have better accuracy than chirp and maximum length binary sequences (MLBS) [75]. …”

Study of excitation signals parameters for portable bioimedical devices

“…But, the increase in measurement speed can cause the loss of the accuracy [12]. In next section, a study of signal's parameters and the effect of their variation on the excitation are expounded.…”

Optimization of multisine excitation for a bioimpedance measurement device

“…The CF [10] is expressed in (3), wherein T denotes the observation time of the voltage or current signal, s(t) and a divisor in this equation represents the RMS value of the signal:…”

“…Optimization of multisine with 11 components i = [1,2,3,4,5,6,7,8,9,10,11] gives CF = 1.372 at optimal phases In the case where all the initial phases are zero, the CF increases to 2.39 (only 3.42 % higher in comparison with optimal phases).…”