How to use your sound card as an oscilloscope

Written by amanda morin
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How to use your sound card as an oscilloscope
An oscilloscope graphs the waveforms of electrical signals. (waveform 20 image by chrisharvey from

An expensive piece of test equipment used to analyse and graph the waveforms of electric signals (AC and DC), an oscilloscope may be out of the price range of most hobbyists. You can, however, simulate an oscilloscope with the sound card on your PC.

Skill level:

Things you need

  • Sound card oscilloscope software
  • Old headphone cable (1/8-inch jack)
  • Soldering iron
  • Solid core wire
  • DC power supply
  • Voltmeter
  • Resistors or potentiometer

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  1. 1

    Download PC sound card oscilloscope software. Some of the more commonly used programs include Zelscope, Audiotester and Scope, which can all be downloaded at little or no charge.

  2. 2

    Configure your PC to record sound via the microphone or line-in port. Though you may not actually be recording any of the signals you'll be capturing, the PC sound card oscilloscope software uses the same interface used to record sound. Double-click on the volume icon in the system tray and be sure both the Line Volume and Microphone Volume levels are turned up and not muted.

  3. 3

    Make a set of probes This requires an old headphone cable with a 1/8-inch phono jack, a soldering iron and some solid core wire. Cut off a long section of the wire and strip the ends opposite of the phono jack. There should be three wires if the phono jack is stereo, only two if the phono jack is mono.

  4. 4

    Solder solid core wire to the ends of each wire. Solid core wire can be plugged directly into breadboards or used as probes. If you want, you could solder banana clips, alligator clips or any type of connector or probe to the ends of the wires.

  5. 5

    Make a voltage divider. A voltage divider is required because your sound card was intended to be used with low-power audio devices. The maximum voltage from your circuit should be around 1.7v. The sound card should be protected against some voltage spikes, but anything above 5v may permanently damage your sound card. A voltage divider can be created with resistors or a potentiometer.

  6. 6

    Test the voltage divider. Since the voltage divider may be the only thing protecting your sound card from the higher-voltage circuit, supply a DC voltage of the maximum voltage your circuit can output. Measure the output of the voltage divider. Remember, you're aiming for an output voltage peaking at 1.7v or lower.

  7. 7

    Start the PC oscilloscope software. Once it has started, you'll see an oscilloscope-like interface. You may also want to turn down the volume of your speakers, since many waveforms can be very loud or even damage your speakers.

  8. 8

    Test your circuit with the probes. Though you won't be able to probe the circuit as freely as you would with a real oscilloscope, you will at least be able to get some information about what's happening in your circuit.

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