7/27/2019 Lab 11 - Capacitor Characterization via Frequency Response
http://slidepdf.com/reader/full/lab-11-capacitor-characterization-via-frequency-response 1/2
Lab 11 - Capacitor Characterization via Frequency Response.docx page 1 of 2
EE221L — Circuits II Lab
Exercise #11
Capacitor Characterization via Frequency Response
I. Objectives
A. The objectives of this exercise are:
The objective of this laboratory exercise is to gain insight into non-ideal (true)
capacitors, including quality and the significance of parasitics (inductance and
resistance) at various frequencies. This will be accomplished as follows:
a) You will create your own test procedure to fully characterize a capacitor,including parasitic resistances and inductances
b) You will perform this test on two separate capacitors of different design (one
an oil/paper electrolytic, the other a polystyrene based capacitor)
c) You will write your own background/theory and test procedure, as thoughthey were to be given to students in future lab sections
II. Introduction
Capacitors
Capacitors are notoriously non-ideal. Based on materials used and the method of
construction and design, capacitors inherently have parasitic impedances due to
lossy material and lead inductance. Figure 1 gives an equivalent model of a
nonideal capacitor. In series with the capacitor is an equivalent series resistance
(ESR) and inductance (ESL), and in parallel is a resistor (Rp) that slowly
discharges stored energy (no capacitor will store charge forever).
C0
ESL
ESR
RP
Fig. 1. Capacitor equivalent circuit model
How does each of these elements influence the performance of a capacitor over a
wide frequency range?
7/27/2019 Lab 11 - Capacitor Characterization via Frequency Response
http://slidepdf.com/reader/full/lab-11-capacitor-characterization-via-frequency-response 2/2
Lab 11 - Capacitor Characterization via Frequency Response.docx page 2 of 2
Your task will be to devise a method for determining each of these parameters.
You can use a multimeter for determining at least one parameter – hint: the
multimeter applies a DC source to your circuit under test when measuring ohms.
The other parameters will be determined through the use of a signal generator and
your trusty oscilloscope.
Before getting started though, you should read pages 650-651 of your textbook.
Once you are done taking measurements, estimate as many performance
parameters from this data as you can, e.g., Q, etc. A plots of data over source
frequency can be very important for this experiment, as well as for your report.
Finally, use the LCR Bridge meter to have it provide its estimate of various
parameters. You can compare these to your own estimates.
III. Procedure
1. Test Setup. Evaluate the model given in Fig. 1. Determine a test procedure to
allow for the calculation of each element (ESR, ESL, C, and Rp). At your
disposal, you have an oscilloscope, DMM, and waveform generator to perform the
exercise.
2. Perform the test on the two different capacitors provided and record enough
information to make the necessary calculations.
3. Test on the LCR Bridge meter.
IV. Post Analysis and Report
Report Content – Format – Experiment (see EE webpage for directions)
1. Write an objective, give a background/theory discussion section, and write
the procedure that you came up with to determine the values of the parasitic
impedances.
2. Produce a results section, which will only give the results of your experiment,
computation of the values of the parasitics found and all relevant graphs/tables.
3. Write your own set of in-depth conclusions answering the question about the
level of quality of your circuit model as compared to the values provided by the bridge meter. Compare the quality of one capacitor to the other. Does one lend
itself to higher frequency applications than the other?