Home Chapter 3 Reading DC Voltages with the Multimeter
Reading DC Voltages with the Multimeter
Book - Chapter 3
  1. Plug the transformer into a wall plug socket. NOTE: The United States and Canada use 115 volts AC and Europe use 220 volts AC.
  2. Turn your multimeter to the DC setting of 500 volts, first image below for this meter.

FDVM810 from Velleman Notice the dial is set to the highest value of Voltage for DC voltage. Most DVM's can be used for this lesson that has AC and DC reading capabilities.


Generally, when you are measuring voltage and are unsure of the range but know which voltages you are dealing with, you choose the highest voltage range possible. You can then work your way down to get more accurate readings of that voltage.

3) Put the red multimeter probe tip inside the silver rounded socket of the end of the transformer wire and then carefully put the black probe tip to the outside of the metal plug.

4) What is your multimeter reading? _________________________________________

5) Now turn to 200 volts DC. What is your meter reading? ________________________________________

6) Now turn to 20 volts DC. What is your meter reading? ________________This is your most accurate reading of the voltage, because your meter setting is closest to the actual voltage of 17 volts.

7) Now, switch your meter probes so the black probe is on the inside of the plug and touch the red probe to the outside of the Save plug. What is your reading on the multimeter? _____________________________________

8) Do you notice the – sign in front of the voltage you read in the window? This means you have your probe tips reversed.

So, when you switch them back so that the red is on the interior of the plug and the black is on the exterior of the plug, you get a positive voltage, but you will not see a + in front of it, as the positive is assumed, but you will see the numbers 17.05 of DC voltage.

Congratulations! You have just measured a DC Voltage.

Extra Fun: If you have some batteries, like 9 volt or 1.5-volt batteries, practice getting the most accurate readings from these batteries.

In Activity 2 we will measure more DC voltages Arduino board or the BS2.