(184v) Multiple Phase Shifted Chirp Signals for Rapid Impedance Estimation: Applications in Diagnosis of Electrochemical Systems

Suresh, R., Columbia University
Swaminathan, S., Indian Institute of Technology Madras
Rengaswamy, R., Indian Institute of Technology Madras

phase shifted chirp signals for rapid impedance estimation: Applications in diagnosis
of electrochemical systems

Resmi Suresh1,
Sathish Swaminathan1 and Raghunathan Rengaswamy1*

1Department of
Chemical Engineering, IIT Madras, India

Email address: raghur@iitm.ac.in




A new approach that uses multiple large
bandwidth and short duration chirp signals for rapid impedance measurement of electrochemical
systems is proposed in this work. The existing techniques for impedance
measurements are not suited for non-invasive, on-line diagnosis of electrochemical
systems as they are time consuming and require the system under test to be idle
during measurements1. In the proposed method, chirp signals in
tandem with a definition of instantaneous frequency are used in the development
of the impedance plots. Unlike the standard multi-sine EIS techniques, where at
each frequency transients have to die down before measurements are made, in the
proposed approach, only the transient data is used in the analysis. An
interesting result from our approach is that while the impedance plots that are
generated are approximate, qualitatively (and to a large extent quantitatively)
they match the true electrochemical impedance spectroscopy plot (EIS plot).
However, the impedance plots are generated using very short duration signals. As
the impedance developed using the proposed technique mirrors the EIS plot, this
method can be used as an alternative to EIS for various applications like fault
diagnosis and optimization studies1. The proposed method improves on
the work presented in Bullecks2 where a single chirp signal was used
for impedance estimation.  Experimental and simulation studies using the
proposed technique (as shown in Figure 1) are included in this work.

Figure 1: Comparison of the impedance profiles obtained using dual chirp analysis with that of the
theoretical impedance



1.             Yuan, Xiaozi,
Haijiang Wang, Jian Colin Sun, and Jiujun Zhang. "AC impedance technique
in PEM fuel cell diagnosis—A review." International Journal of Hydrogen
Energy 32, no. 17 (2007): 4365-4380.

2.             Bullecks, Brian,
Resmi Suresh, and Raghunathan Rengaswamy. "Rapid impedance measurement
using chirp signals for electrochemical system analysis." Computers &
Chemical Engineering 106 (2017): 421-436.