Introduction: Use Your Laptop As Oscilloscope

Picture of Use Your Laptop As Oscilloscope

Oscilloscope is an electronic test instrument that allows projection of voltage signals to be displayed and learned. A specific circuit in the oscilloscope creates repeated moving signals from left to right. This repetition creates non-repeating waveforms that can be learned.

Oscilloscopes are commonly used to observe the exact wave shape of an electrical signal. In addition to signal amplitude, oscilloscopes can show time distortion between two events (such as pulse width, period, or rise time) and relative timing of two related signals

Below is a picture of common Oscilloscope.

Today, Oscilloscope uses LCD color display, displaying better graphics

Step 1: Make Your Own Oscilloscope Using Your Laptop Computer

Picture of Make Your Own Oscilloscope Using Your Laptop Computer

Once I need an oscilloscope to see the electrical voltage ripple in the car. Ignition systems, alternator rotation, high-beam lights flicker, and others are generally emit noise or voltage ripples, Well, this is what I want to know, size of the noises, etc.

Oscilloscopes are very expensive tools, and generally are only used in electronics / electrical laboratory.
Finally, I found an application that could use laptop computer / PC as Oscilloscope by adding some components as interface.
Those components are simple and quite cheap!

The necessary components:
• Two 22K ohm Resistors
• Two 82K ohm Resistors
• One 50K Linear Potentiometer + Tuning Knob
• One meter Shield Stereo cable
• One 3.5mm Stereo Jack
• Tester Terminal

Step 2: Electronic Scheme

Picture of Electronic Scheme

• The 22K Resistor serves as voltage safety limit into laptop soundcard.
• The Potentiometer serves as input voltage resistor. If the voltage is above 5volt, adjust the potentiometer necessarily to prevent the soundcard from being damaged by excessive voltage input.
• Use shield audio cable to prevent induction around the cable.

Step 3: The Probes

Picture of The Probes

Attach the probes

Step 4: Testing

Picture of Testing

The unit is ready,

Plug the Stereo Jack into LINE-IN/MIC

The application is ZELSCOPE, free download at .
This application is 14-day Trial, could be purchased at a price of not more than (US $9.95).

The Oscilloscope is ready for use!!
Below are several voltage signal tests, among others signals from mobile phone charger, laptop charger, battery, etc.
Sample of close-to-perfection voltage signal without noise.

1. This Oscilloscope could be used for a maximum input voltage of 5Volt.
2. This Oscilloscope has a frequency range of: 20Hz to 20 kHz (complying with the Soundcard capability).
3. The value of 22K Resistor could be increased up to 820K Ohm for the use of Oscilloscope with an input of above 5 volt.
4. The value of Potentiometer could be increased up to 100K Linear, for the use of Oscilloscope with an input of above 5 volt.
5. For safety of your Laptop, you can use cheap USB SoundCard (under $5).

Good luck.


Translated by Taufik Masjhur
This post was originally published on in Bahasa Indonesia language.


DonnH1 (author)2017-11-08

Nice to see someone added blocking diodes to protect the circuit and also protect the PC. I had a friend, retired nuclear physicist, a really knowledgeable guy. For some reason he used a couple of very expensive, very elaborate, oscilloscopes (one after the other) to see a trace of an auto ignition system and ruined the front end of both. Be careful and you can do a lot with this little circuit.

illumation_ (author)2017-08-15

I really like this. Good tool to get familiar with scopes. I want to use a defective cheap multimeter to house a cheap sound card (to test and avoid damage and it is USB) and all the components you mention here. The selection knob can be the fine-tuning knob and you can use the standard available probe connections. You can also remove the faceplate (because it is a sticker) and print your own faceplate for it. Sounds pretty cool right? I will post it here when my approach is successful. Thanks for sharing this.

AlaK5 (author)2017-05-26

can i use this circuit for a smartphone .. i know that there is another methode for phones but i like this one .. does this work for pc and smartphone ?

taras_masnyj (author)2017-03-23

Another software Oscilloscope

There are several versions of this free software oscilloscope program. Google it. It can also use the PC microphone input as a signal source.

rrozzers (author)2017-03-16

ps. I did use a pair of zeners between the rails.

rrozzers made it! (author)2017-03-16

great instruction. Really clear. The scope software is great for low frequency sensors, drives & audio applications. The fact that there is a signal generator incorporated into the software is really good.

BryanS83 (author)2017-01-05

You say in the Instructable: "

The application is ZELSCOPE, free download at .
This application is 14-day Trial, could be purchased at a price of not more than (US $9.95)." But , in the comments you said, "

The software you can use is: ." This one (Soundcard Oscilloscope) you use in the "PC SOUND-CARD SCOPE INTERFACE FACILITATES DC RESTORATION" Instructable. Can the Soundcard Oscilloscope be used for BOTH projects? Also, I want to measure the frequencies of a Tesla Coil and other HV/HF devices. Can I use, for example, a transformer and current-limiting resistors between the Tesla Coil and the O-scope leads to protect my computer?


ali_12 (author)2016-12-14

I need oscilloscope to show output wave 220 volt Ac.what should i do?
Thank you

aagrafi (author)2016-10-31

Hi, I want to use my laptop as both oscilloscope and signal generator. In such case, how can I separate the signal of the signal generator (output), from the signals to the oscilloscope (input)? Do you have any circuit diagram that does this?

Yonatan24 (author)2016-01-31

Hi, I've added your project to the "Make Your Own Oscilloscope!" Collection

This is the link If you are interested:

ajoyraman (author)2013-05-29

Great minimum component interface ! For safety/protection I suggest you add a couple of back-to-back 2 X signal diodes across the 82K resistors which would restrict the sound card input voltage to approx 1.4 V.


sparkgaptime (author)ajoyraman2015-12-19

you have 2 of the diodes not in their correct polarity, back to back diodes will work as long as ratings are not exceeded, however this diagram will cause a short and could damage an already very poor person's personal computer!! This is totally unacceptable. Back to back diodes is usually implying one forward biased diode in series with one (respectively) reverse-biased diode(usually identical diode model).

ajoyraman (author)sparkgaptime2015-12-20

Yes, the terminology 'back-to-back' is incorrect. What I have suggested is two diode-pair clamps with opposite polarities. When the input voltage exceeds ~ 1.4 V of either polarity it is clamped by the diode-pair and the rest of the voltage is across the input series resistance. This resistance also acts as a current limit.

fdhrubo (author)ajoyraman2014-06-17

is it fully safe now? if I add the 4 resistors? i am trying to build 1. And what software can I use for this?

ajoyraman (author)fdhrubo2014-06-18

It is quite safe as long as you remember that the ground of the PC is not isolated and so we should avoid measuring the AC mains or other circuits not isolated from the AC mains.

The software you can use is:

This instructable uses passive components and the impedance of the sound-card may attenuate the voltage inputs.

You can also see my instructable which uses active components:

ChrisR16 (author)2015-04-22

Hi, all looks very good, but changes would I need to make to have to measure up to 250V with current up to 20A? Just have thicker wires? Thanks

velmonte10 (author)ChrisR162015-12-11

i guess u can put a stepdown transformer, a resistor and a capacitor into thr circuit.

The transformer will lower the voltage.

For the capacitor, make sure that the inductive reactance of thr transformer is equal to the capacitive reactance so that the added RLC circuit wont affect much the waveform produced by the ac generator ur working in. And the resistor will lower the current.

This is just my theory.. i hope it helps..

Jimut (author)ChrisR162015-05-31

Good Luck on blowing up your laptop

pede69 (author)2015-10-30

Everything I would use this for opperates from 12 to 15 volts. Can you provide mods to make this work in that range?



KaivitiSingh. (author)2015-10-20

Has anyone got a pure sine-wave displayed on this oscilloscope??? and also how to get rid on the flicker which happens all the time as soon as you press play button.

KaivitiSingh. (author)2015-10-20

Has anyone got a pure sine-wave displayed on this oscilloscope??? and also how to get rid on the flicker which happens all the time as soon as you press play button.

AhmeedS (author)2015-10-18

problem with software ,the error msg:-

For security purposes, this program will not run while system debuggers are active. Please remove or disable the system debugger before trying to run this program again.

wendesen (author)2015-09-02

drmainu78 (author)2015-08-29

JesperK (author)2015-07-18

To hold it up against a textronic or other expensive scopes is not fair. It is a very good solution to low frequency measuring. For education or hobbying it is a cheap and fine way for a start..

Great idea, thumbs up

mahtab93 (author)2015-07-15

pleas help meeeee i want design oscilloscope with gui in matlab but can not download this pdf helppppp me send my mail i neeeeeeed

send my mail


TonnyC (author)2015-07-14

even tektronix mdo 3000 series perform better than this software

vidavaliente1 (author)2015-04-10

what is the maximum voltage that can be measured exactly and be shown on the scope. as i'm using encoder that should have maximum voltage 5v.
while the maximum voltage appeared on the scope is 300mV

Jimut (author)vidavaliente12015-05-31

It attenuates the input voltage to about 700mV, which is the maximum input voltage for an audio source. So, you are seeing the input as 300mV. If you want to calculate the actual voltage we will need to find the attenuation ratio of it with respect to the voltage divider formed by the pot and calculate it out, which is a pretty hefty job to do every single time.

3dfernando made it! (author)2015-04-09

Made it! Thank you, bro! Solved my problem of measuring impact behavior in AC motors!

ajoyraman (author)2015-03-05

The M-Audio Revo 5.1 is basically a high performance PC add-on audio card. The main feature is a sampling rate of 196 kHz compared to 96 kHz of most other cards. This means that the maximum signal frequency that can be seen clearly while using it as an oscilloscope would be around 20 kHz. The audio input levels would be typically +/- 1.4V which would also be capicatively coupled. This Instructable provides a simple resistor network to attenuate larger voltages. It also uses a Sound-Card oscilloscope software.

Regarding the probes: The frequency response of probes determine the max-frequency that the probe passes but finally frequency limit is from the card which is much lower. Also probes are used with active input circuits with typically 1 MOhm impedance which not be met by the simple pot-divider scheme presented here.

Overall this may not be a suitable scheme for observing high frequency signals.

JanM5 (author)2015-03-04

I'm trying to build somehow functional oscilloscope (best bang for buck ratio). Got second-hand M-Audio Revo 5.1 which has 24-bit 96kHz ADC, AKM 5365 ( At some point I'll consider active circuitry, but right now I'd like to test and play with it using passive interface. By any chance would you be able to advise best Vmax for the input? I've read that it has "Auto Level Control (ALC) Circuit", but I'm not very smart about it. And "ANALOG CHARACTERISTICS" table in the datasheet is just overwhelming for me :( One last thing which would help a lot, there are many passive oscilloscope probes out there, most confusing for me is frequency and capacitance (I have some idea what resistance means there :)). Does it mean I'll have to buy multiple probes in order to have some reasonable range of the freq. specter or is there some way to choose one suitable for sampling rate of the card. Target is to be able to see various digital signals (e.g. DHT11, FHT8V, IrDA, nRF24L01+), so some flexibility would be great.

Any suggestions are welcomed!

hubble07 (author)2015-01-07

Hi, I wish to build this circuit. However, I don't know if the pot used is a dual gang pot (stereo pot) or linear pot. I have got one which has 3 pins. Can I use that? Please forgive me if I am being ignorant.

sam.gwilliam (author)hubble072015-02-15

I believe it's dual gang as you'd want to keep signals A and B proportional controlled by the same knob.

>signals A and B proportional controlled by the same knob.

And kept separate.

sam.gwilliam (author)2015-02-15

What is the purpose of the voltage divider (i.e. 2 82k resistors) connected to ground?

paulieux (author)2014-07-04

What should you do if you want to use it as a sound detector? What modifications should be done, like you will use microphone to detect the sound and find out its wave form in the software?

kf4nxs (author)paulieux2015-01-26

what you need is a spectrum analyzer

pffm12 (author)paulieux2014-07-05


You don't need to build nor modify anything for that purpose. Connect the microphone to the computer, open the software and there you go. You'll see the wave on the screen.

paulieux (author)pffm122014-07-11

Thank you, but what if the microphone has a big stereo jack which is not compatible to be inserted in the soundcard?

pffm12 (author)paulieux2014-07-11

Use an adapter.

ColbyH (author)2014-11-12


You may look closely at your headphone port, it might have a picture of the headphones symbol as well as the microphone symbol.


My laptop has a single port that does both.

dcp30 (author)2014-11-03

Hi, what is the wattage on your resistors and the 50K pot? I went to purchase the necessary components, and found that the wattage varies from 1/8 watt to 1/2 watt (and possibly more that I didn't see). Good job, btw.

urane (author)2014-10-27

My lapptop has no mic i/ has inbuilt mic

pffm12 (author)2014-06-29


I am finding trouble with this. If you plan to use this project to see noises or similar, like the author, it's OK, but if you want to use it like a real oscilloscope, if you want to see the waves shapes this is not going to work (I reckon).

I've made some measurement in 2 computers with crappy built-in souncards (which I hope are better than USB chinese ones). I've measured the maximum voltage you can put straight in them (in mic input as well as line) without distort the perfect sine wave I used.

The results are:

For a Realtek, Mic: 10 mV, Line: 100 mV

For a Sygmatel, Mic and line: 125 mV

You can put 1 or 2 volts directly and it won't break, but the pure wave gets cut, or distorted if you pass the very low voltage levels I indicated. As an example, on the Realtek, if you put it just 0.5 V, the sine wave looks almost perfectly square because of the cuts.

The problem is, if you want to solve that with a voltage divider, it'll have to be massive. I don't think this project is viable for other purpose than see noise.

fdhrubo (author)2014-06-17

what software can i use??? I need a freeware.

pffm12 (author)fdhrubo2014-06-29

This is by far the best oscilloscope software, and it's free for educational and non-commercial uses. Anyway, another fully free soft is 'BIP Electronics Labs 3.0 - Oscilloscope'.

phmanzano (author)2014-02-11

By ignorance (or laziness or cut-the-corners mentality), I tried the free JOszi (, java) without anything but an audio cable plugged in my laptop.

Reading this instructable and all you comments I guess I was lucky because I didn't fry a thing. Here is the kind of result I got.

I wonder if a cheap USB soundcard can act as "breaker"?

wyatt8740 (author)2013-12-02

I'd definitely add a 5.1 volt zener diode and a 3 or 2 ampere fuse. This would protect against overvoltage relatively well. I'd also use an external, powered USB hub. This would further prevent damage to your computer from excess voltage.
When you don't know the voltage you are about to measure, test with a multimeter, and if it is too high for a 22Kohm resistor, add a bigger one to it until it is a safe level.

astral_mage (author)2013-11-28

true the cheap usb sound card should in theory burn b4 yr laptop does.

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