# Inductance meter with Arduino and LM393

Here it is shown how to make an inductance meter with Arduino and LM393 operational amplifier. The Arduino is used to send short pulse to an LC circuit, where C is known value of capacitor and L is the inductance to be determined. The output of the LC tank circuit is then fed into the LM393 comparator. The output of the LM393 is then measured by Arduino using the pulseIn() function. The measured pulse duration is then used to calculate inductance value from the known frequency and the capacitor value using the formula.

$$f = \frac{1}{2 \pi \sqrt{LC}}$$

from which inductance is determined.

$$L = \frac{1}{4 \pi^2 f^2 C}$$

You can also use the following LC parallel resonant circuit online calculator.

The following shows the diy inductance meter using Arduino and LM393.

The following picture shows the LC circuit build on perfboard. The capacitor is 0.114uF which is soldered fixed and the unknown inductor can be inserted into the hole type header.

And the corresponding schematic diagram of the inductance meter is shown below.

In the above circuit diagram, a pulse is sent from Arduino pin 12 to the LC tank circuit made by L1 and C1. The capacitor C1 is of known value and should be accurate. The inductor L1 is the unknown value. The inductor is inserted to determine its value. The output of the LM339 comparator is connected to Arduino pin 10. The Arduino is used to measure the pulse duration of the pulse coming out of the comparator which is due to the LC tank circuit. The pulseIn() function is used to measure the pulse duration. The diode D1(1N4001) prevents the LC tank generated pulse to go back into the Arduino pin 12 which could damage the pin.

The following video shows animation of how an inductor inductance can be measured with the above circuit.

The following video demonstrates how the inductance meter works.

Project Files

You can download the Inductance meter with Arduino project file below.

Also if you want DIY home electronics testing tools then see the following tutorials.

- How to use Matlab Simulink as Oscilloscope