Vernier Software and Technology
Vernier Software & Technology
Tech Info Library

How can I generate a clean sine wave output from a LabQuest?

LabQuest includes an audio function generator, as well as an internal speaker. The speaker can be used to hear a waveform, but due to the small size of the speaker, harmonic distortion is significant.

If you want to use a microphone to see the waveform produced, you'll want to use external speakers. Powered computer speakers work well.

The Logger Pro file below shows the same 400 Hz sine waveform, using computer speakers and the internal speaker. The sine waveform is distorted when produced by the internal speaker.

http://www.vernier.com/til/files/2274/2274-labq_speaker_waverform.zip

The FFTs of each show that the internal speaker produces significant harmonic distortion, while the external speaker produces little.

See also
TIL 662: What is the best procedure to get a clean sine wave when using a tuning fork with the microphone?
TIL 667: How do you change the bin size of an FFT in Logger Pro?

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