PASCO WA-9867 Sine Wave Generator - Manual (Page 13)

Model No. WA-9867 Applications
13 ®
Vibrating String
This automated display of a vibrating string is a good example of where the Advanced Mode is
useful. With a 2 meter elastic cord and the PASCO String Vibrator (WA-9857), you can easily get
a standing wave of 10 segments or more.
In this demonstration, the Sine Wave Generator scans through the resonance frequencies so that
you see the string vibrate with 1, 2, 3, etc., segments. The generator is mounted vertically to
display the driving frequency. Once set up, it will cycle indefinitely, making for an engaging
permanent display.
For best results, use Advanced Record and Playback Mode. If you were to use the regular Auto
Play mode, there are two problems that would occur. First, the optimal driving-signal amplitude
for the lower harmonics would be insufficient to excite visible vibrations at the higher harmonics.
Second, it would be difficult to perfectly tune a single increment value so that the driving
frequencies for all 10 harmonics were exactly correct.
Both of these problems are solved with Advanced Mode, since you store both the frequency and
amplitude of each note in the sequence. Because the Sine Wave Generator is working as you
record the sequence, you can finely tune the driving signal for maximum effect at every harmonic.
See the Advance Mode section on page 7 for programing instructions, and the PASCO String
Vibrator manual for mechanical details of the setup.