The DMM (Digital Multi-Meter) is a Stethoscope for Electric Circuit.

Caution: Be careful for the safety! Electricity is very dangerous and very hot sometimes, so you may burn your finger!

Tools: Digital Multi-Meter, Battery, Battery Holder, Socket, Light Bulb, Aligator Clip, LED

It can be used in different ways.

Here are typical examples of how to use DMM.

(1) Measuring dc voltage

I made two 3.2V DC with four 1.6V DC battery with two holders.
I only thought that batteries were only 1.5V. However, when measured, the instrument shows 1.6V.
The series connection of the two 1.6V batteries creates 3.2V.

(2) Measuring ac voltage

AC indoor power line in Korea has 225.3V
Koreans normally call the power line’s voltage 220V. However, it is actually 5.3V higher.
Compared to the American power line, Korean power line is more lethal.

(3) Measuring dc current

The indicator shows that the current flowing through the small light bulb is 29.5mA.
The supplying voltage is 3.2V.
The (working) resistance can be calculated with Ohm’s law.
V=iR.; 3.2V=29.5mA*R
R=3.2V/29.5mA=3.2V/0.0295A=108.47
The room resistance was 4.2ohm at 25oC.

(4) Measuring temperature

Digital Multi-Meter can be also used as a Thermometer.
I positioned the temperature probe between my armpits.
It says that my body temperature is 37oC.
There could have been an error because a cloth blocking my body and the probe.