the Technology Interface/Fall
96

A Simple Procedure for Measuring Inductance

by
Guillermo Rico
[email-masked]
Department of Engineering
Technology
New Mexico State University

This method
requires the use of a signal generator and an analog or digital multimeter.

1. Measure the wire resistance of the inductor under measurement; call it r.

2. Assemble the following circuit using a known resistance R between 100
S and 1
KS. Adjust the
generator to a frequency of 2 to 10 KHz, sine wave, and 1.00 volt rms. The
voltmeter must be connected across points A and B, that is, reading the voltage
from the generator.

3. Move the voltmeter test leads across points C and B and take down the
reading; call it x.

4. Substitute your values into the following formula to determine the
inductance L.

CIRCUIT ANALYSIS

Using
voltage division, the output voltage can be expressed as

Let x be the magnitude of the transfer ratio. Then,

If
we use a source voltage of 1.00 V, then x will be equivalent in magnitude to the
output voltage VO. Therefore, we simply have to solve for
XL in order to obtain the inductance value in terms of x, resistance
values, and frequency.

Square
root both sides and replace XL by 2BfL to obtain

If you have questions for Dr. Rico
click on his name.