Sound Card Oscilloscope
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Oscilloscope
Every computer today comes equipped with a relatively good sound card. A sound card can digitize sound from a microfone for recording, and play digital music through computer speakers. It is not uncommon to find sound cards that can digitize sound waves at rates of 100 kilo-samples per second with 16 bits. This means that any signal, in principle, could be examined with this sampling rate. In other words, a digital oscilloscope with 100 kilo sample per second can be built.
But there are few issues. A bench oscilloscope is a device such as the voltmeter with regards to the input impedance. When connected to a circuit to be examined it should not interfere, and hence the input impedance should be at least 1mega Ohm. Sound cards have a very low impedance input, and therefore connecting it to a circuit it would result in an erroneous measurement. Normal measurement using a microphone is of course allways possible.
The output of the sound card could be used as a waveform generator to, for example, excite a circuit. For this to be possible digital waveforms need to be synthetized by software.
Software
http://www.zeitnitz.de/Christian/Scope/Scope_en.html
This software also allows you to generate waveforms. The software is particularly useful to measure speed of sound, and perform a number of experiments that uses microphones as sensor.
Oh yes, send Christian an email saying that you're using this software!
High Impedance Input
When using sound cards beware that they have low impedance. This means that when you connect to a circuit it will affect the circuit. To prevent this you have to build a little circuit. This web site has intructions on how to build one.
Tips to use the Scope
- The scope input and output are controlled by Windows control panel, Sound settings.
- The scope has a built in waveform generator.
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