How to Use a (Simple) Oscilloscope!





Introduction: How to Use a (Simple) Oscilloscope!

About: Dabbled in dark matter, settled into engineering with a blend of inventing and teaching, always trying to solve problems + learn new things!

Visualize all those mysterious electronic signals with an oscilloscope!

Learn how to build and use a super simple $30 oscilloscope perfect for electronics hobbyist applications. It's also a great way to get started using some of the fancier oscilloscopes!

Step 1: Reading and Changing the Oscilloscope Display

Every oscilloscope has a window that displays the voltage output of your signal.

In every display, the y-axis is voltage, and the x-axis is time.

You can zoom in and out of the display grid by adjusting the "Volts per division"* or "Seconds per division".

On this oscilloscope, the voltage adjustment switches are on the left side (Photo 2 -- bottom two switches), and they let you zoom out to as much as 5 Volts ("V") per division, and zoom in to 10 mV per division.

Adjust the time scale using the "+" and "-" buttons on the right side (Photo 3).**

*"Per division" means the size of the squares, e.g. 1V per division means that each square is 1V in height, 1 second per division means that each square is 1 second wide.

** Be sure that the time scale is selected (will be highlighted with a box around it -- this is the default selected setting, change settings using the "sel" button, described in more detail in the next section.

Step 2: Other Basic Features

This oscilloscope has all the fundamental features of larger, more expensive 'scopes, and also is a great introduction to some of the more complex versions.

On the left side, the top switch allows you to choose between a ground signal, a DC signal, and an AC signal. On the right side of the oscilloscope are four buttons:

1. The "ok" button (very top button): Pushing it once takes a snapshot of the screen, which can be saved to the oscilloscope. Holding this button down displays key numeric values about your signal, like the maximum and minimum voltage, signal frequency, etc.

2. The "+" button: Similar to an up arrow key, pushing this button allows you to sort through options.

3. The "-" button: Same as the + button, but, you know, scrolls down.

4. The "Sel" button: Pushing this button allows you to select different features (described in order):

A. Change the time scale.

B. Set how the oscilloscope display refreshes - "Auto", "Norm," or "Sing". More on these in the next section.

C. Set the trigger slope. More on this in the next section.

D. Change the trigger level. More on this in the next section.

E. Adjust the horizontal position of the oscilloscope display.

F. Change the vertical position of the display.

Step 3: Oscilloscope Trigger

Oscilloscope triggers cause the oscilloscope to display a signal. Triggers are set at a specific value, or "trigger level," along a specified direction, or "trigger slope" (more info below).

The trigger helps to display the exact electrical signal that you want, so that you get a stable display and measurement. In this 'scope, the trigger is set on the right side of the display and the LED at the bottom flashes when the trigger is detected.

The simple oscilloscope in this tutorial has three trigger modes that you can switch between using the "+" and "-" buttons:

  1. Automatic ("Auto"): Display continually refreshes, regardless if triggers are met.
  2. Normal ("Norm"): Display only refreshes if the trigger is met.
  3. Single ("Sing"): Same as normal mode, waveform display is held after a trigger has been detected.

More on Trigger Level and Trigger Slope!

The Trigger Level is a set, internal voltage that is compared to the signal, or input, voltage. The oscilloscope triggers when the signal voltage is equal to the trigger voltage. If an electronic signal rises and falls, then the trigger would happen twice: once when the signal is rising and again when the signal is falling. The trigger slope lets you choose which voltage (rising or falling) to trigger on.

Step 4: Connecting a Component

Now, to see the electrical signals at work in the world around you, connect the black lead to ground, and the red lead to the part of the circuit that you want to measure the voltage.

For example, if you want to measure the voltage output of a sensor, like the capacitor in the second photo above, you want to connect the red probe after the sensor.

You may also want to calibrate your scope using the on-board signal. See the datasheet for more info.

Step 5: Turning on the DSO138 Oscilloscope

The an oscilloscope kit in this tutorial takes about 2 -3 hours to assemble (instructions here), but it is definitely worth building because many reasons! Here's a few: it's a great way to learn circuit components, get familiar with schematics, and practice soldering (and de-soldering....). And, honestly, it's pretty relaxing.

Once you've got the 'scope assembled, it needs 9V and about 0.1A. There are two power ports: a barrel jack and a male JST connector. You can use a 9V battery with the barrel jack (OMG it's portable!), or a power supply with the JST connector.

The exposed wire on the top of the oscilloscope is a square wave signal to help you calibrate the signal (see the datasheet for more info).

Be sure to use less than 12V or you risk heating up the board and possibly damaging it (don't let the black smoke out!).

Step 6: Plug and Play!

Now you know all the basics to connect your oscilloscope to sensors, your tongue, and other low power sources to watch the wonderful world of electricity at work!

Please leave a comment in the tutorial if you have any questions or would like more info about the oscilloscope kit. Now go forth and explore all that electricity! :D

Interested in building a capacitive touch sensor like the one used in this tutorial? Check out this tutorial!

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36 Discussions

Please do a follow-up tutorial on how to use this scope. It would be of great help to newbies like me!

Mine only shows 9mv :( no matter where I connect it or...

1 reply

Do you have an adequate power supply? Did you try using the zoom in and out features or changing the display? It could also be a faulty connection, so once you've exhausted all other options, I'd go back and double check the schematic and compare it to yours. Best of luck figuring out the issue!

and now the working info ,so i mean try some things out and explain it.

i see this as a gearbest advertice, not as a INSTRUCTABLE

4 replies

I don't really mind that, as I've been looking for a cheap o-scope to use for stereo tweaking in my car. My issue is that I'm lazy and don't want to have to put the whole thing together and the advertisement is full of contradictions. It could be a kit with bags full of parts, a partially assembled kit, or ready to go out of the box, depending on which part of the page you believe.

The one that I've linked to in the tutorial is a partially assembled kit -- the ICs and other small components are already assembled, but you have to solder on the through-hole components (resistors, capacitors, connectors, etc.). It takes about 2-3 hours, but is pretty easy and a good practice in soldering and identifying circuit components.

Appreciate the feedback. In my case it isn't that I'm not capable of the soldering, as I was a bench tech in another life. I just did so much of it that if I never hold a soldering iron again, it'd be fine with me.

Anyone know if there is a completed version available?

Thanks to a great suggestion from a helpful commenter, I'm thinking of adding a second tutorial on measuring simple circuits w/ the oscilloscope. Regardless, gotta give props to the awesome folks that donated the kit for educational purposes!

And if you are thinking of buying one, I would also recommend buying these cheap acrylic laser cut cases.

2 replies

Thanks for the link! I just went and bought one. When I bought mine I looked for a case and there was not any.

These cheap little kit scopes are great for learning electronic fundamentals, but no so much for troubleshooting or practical use. I recall a couple of Heathkit courses that required an oscilloscope -- too bad these little gadgets were not available back then.

Note: I built one of these scope kits, the one where you had to solder the SMD ICs and resistors yourself. Difficult, requiring much patience and a fine touch, but doable.

1 reply

Yea it's a good introduction to oscilloscopes, definitely not lab-grade but for the price it's a great option for hobbyist projects!


1 year ago

I like to use one on 120 volt AC to see the sine wave.

What would I have to do and how would I hook this up to it?

3 replies

I would advise extreme caution if you intend to use one of these on mains supplies or any other source of voltage above 50 volts. Without wishing to be offensive, if you need to ask the question you should not even be thinking of working on mains supplies.

Thanks a ton for the helpful responses, llanE1 and JUANKERR!

I would also reiterate that this scope isn't rated for 120 VAC, so if you are new to this type of thing I'd recommend starting with something smaller and safer.

You must always be mindful of the maximum voltage you're allowed to put into the 'scope's probe. Lets assume it says MAX V IN 12V peak-to-peak. You'd build a voltage divider made of two resistors [preferably in the 10s of Kohms range, so that they don't heat too much], so that you divide your 120VAC, which reaches peaks of 170V into parts, say one that is 19/20 of the total and one that is 1/20 of the total. On the smaller resistor you'll have the same waveform, but only some 8.4 V peak-to-peak, and you can connect your 'scope probe across this resistor to display.

I was hoping to see some information on practical ways of using this tool - I built one myself a couple of months ago. I'm still learning about electronics and would like to see some instruction on how to use it for fault testing or whatever else you use these things for.

1 reply

Oscilloscopes are helpful for visualizing signals that change over time, e.g. PWM, AC, etc. For example, if you are trying to turn on a voltage source for a certain amount of time, like 1 s, then turn off the voltage, and repeat this to get a square wave, you can use an oscilloscope to actually see the square wave signal and check if it has the frequency/amplitude that you want.

It's also super useful for finding noise in your signal because you can zoom in/out and see if there are interfering waveforms over your signal.

Hope that helps, LMK if you have any questions about this!

I have a similar scope and I do not think the voltage measurements are very accurate, (you have multimeter for that job!) but the wave shapes and frequency measurements are very useful. I give these little units a ten out of ten for normal debugging and educational purposes