# How to use a Digital MultiMeter

One of the most useful tools a scientist can have! A digital multimeter can quickly help you discover where the trouble is in your electrical circuits and eliminate the hassle of guesswork. When you have the right tool for the job, it makes your work a lot easier (think of trying to hammer nails with your shoe).

We’ll show you how to get the most out of this versatile tool that we’re sure you’re going to use all the way through college. This project is for advanced students.

19 Responses to “How to use a Digital MultiMeter”
1. Aurora says:

Look at one of the starting experiments – “Basic Circuits” – do you see it? There are complete instructions.

2. Aurora says:

Me too! A DMM is super-useful!

3. cmsobleo says:

I LOVE THIS

4. cmsobleo says:

how do you hook up a LED

5. Aurora says:

It depends on how salty your water is. If It might be interesting to see how electrical resistance (make sure you are measuring ohms here) changes as you add more and more salt. You can keep your LED hooked up in the circuit as you do this as well. Great job being curious! Do let me know what you find out!

6. andrea alfred says:

We were experimenting with our digital multimeter and had a lot of fun. We combined this experiment with testing a circuit with LED. Everything with a low resistance reading also lit the LED, except when we tried saltwater! With saltwater the LED lit up dimly, and we had too high resistance to read on the multimeter. We wondered why? We thought saltwater would conduct electricity well. Do you have any idea what is going on?

7. Aurora says:

Can you send me a photo of your multimeter so I can point out the functions and setting you want to use? Use [email protected] to send the photo.

Which 20 should I use? There are 3. (20, 20m, and 20k)

9. Aurora says:

It depends on what the range of volts or amps are that you are testing. For most of the circuits in our program, the 20 setting will work just fine. If you’re getting a zero reading, then switch it down to a lower value, and if it’s pegged too high then you’d switch it up a decimal place or two.

What I mean is, what setting does it need to be on to test a circuit board?

11. Aurora says:

It depends on what you want to do. For the video, put it on the “20” setting.

What setting does it need to be on?

13. Aurora says:

Yes absolutely!

Can I use my multi-meter to test a circuit board that isn’t working?

15. Bessie Woodie says:

great video!! thank you!!

16. Aurora says:

For conductivity, you are testing for resistance, so you want that number as low as possible. If you read 150, then you’re measuring resistance and it’s going to have a drop in voltage where you might not want it. Wires should have a resistance of below 10 to be good conductors of electricity.

17. Michelle Palmer says:

When testing for conductivity at the 31:50 minute point of the video he says if it registers below 10 it tells us something is good. What if something registers above 10? I had something register at 150. What does that mean?

And does he mean the lower the number is the better?

18. Anne Larsen says:

We used the DMM to measure the voltage across a motor in our simple 3volt circuit and were getting crazy high readings. Swapping out the motor for an LED, the measurements were as expected ~2.5 volts. Can you please explain 1) why the motor was generating false high readings and 2) how to get an accurate measurement.

19. Cindy Hoskins says:

this is very cool! i like to do this. ðŸ™‚