Circuit equivalent for fitting my data

In summary, the conversation discussed experiments with impedance spectroscopy and the difficulty in finding an equivalent circuit that fits the data. The equivalent circuit was found to be similar to the data, but there was an issue with the resistance dropping at low frequencies. The question was posed of what circuit element or action could be taken to address this issue, with the suggestion of a component whose reactance decreases as frequency decreases. The dip in Z'' indicated the presence of a resonant circuit.
  • #1
MarkTheQuark
5
2
TL;DR Summary
Impedancy Spectroscopy
I did a few experiments recently of impedance spectroscopy, and I've gathered some data that i'm having some issues to find an equivalent circuit that can fit the data.

The equivalent circuit that I've got, it's pretty similar with the data (graph and circuit below)

But the problem is, at low frequencies, my data values drop, while the fit from the circuit keeps going up.

Z' represents the real part from the impedance, so basically I need to my equivalent circuit to drop the resistance at low frequencies.

What circuit element, or what I could do, so that I could find an equivalent circuit to my data?
 

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  • #2
Can you think of a component whose reactance (impedance) goes down as the frequency goes down?
 
  • #3
The dip in Z'' suggests there is a resonant circuit somewhere.
 

FAQ: Circuit equivalent for fitting my data

What is a circuit equivalent in the context of fitting data?

A circuit equivalent refers to using an electrical circuit model to represent and analyze the behavior of a real-world system based on experimental data. This involves creating an analogous circuit that mimics the system's response, allowing for easier interpretation and prediction of system behavior.

How do I choose the right circuit model for my data?

Choosing the right circuit model depends on the characteristics of your data and the physical principles governing your system. Common models include simple resistor-capacitor (RC) circuits, resistor-inductor (RL) circuits, and more complex combinations. Analyze the frequency response, transient behavior, and other relevant parameters of your data to select the most appropriate model.

What software tools can I use to fit my data to a circuit model?

Several software tools are available for fitting data to circuit models, including MATLAB, LTspice, and specialized tools like ZView for impedance spectroscopy. These tools offer various functionalities for parameter estimation, simulation, and optimization to match your data with a circuit equivalent.

How can I validate the accuracy of my fitted circuit model?

To validate the accuracy of your fitted circuit model, compare the model's predictions with experimental data that were not used in the fitting process. Additionally, perform statistical analysis such as calculating the root mean square error (RMSE) or using goodness-of-fit metrics to quantify the model's performance.

What are common challenges in fitting data to a circuit model?

Common challenges include selecting an appropriate model complexity, dealing with noisy or incomplete data, and ensuring that the fitted parameters have physical relevance. Overfitting, where the model becomes too tailored to the specific dataset and loses generalizability, is another frequent issue. Proper preprocessing of data and iterative refinement of the model can help overcome these challenges.

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