Node Counting Circuit for Standing Wave Generator

[Fdtroya]

Summary: Make a circuit that counts the number of nodes in a standing wave generator

I have a an assignment to complete this Term, the assignment consist in making a machine that would produce standing waves in various frequencies, (for example the typical motor connect to a string with variable tension that creates various standing waves)

the complexity of this assignment is that I have to implement a circuit that would basically know or "count" the number of nodes in the wave depending on the speed of the motor and on the tension, then I would have to display That number through the voltage reading of a multimeter at some stage of the circuit . This number should match the quantity of nodes in the standing wave at that moment.

I can not use Arduino, and am basically limited to using resistors and capacitors, maybe I can persuade my professor to let me use other components. I am sorry if I have not been very clear, English is nor my first language and I'm kind of confused with this assignment, I have some basic ideas of what I could do but I don't think they would work. Thank you for you answers.

 

[Baluncore]

The number of nodes will be proportional to the length of the string in time, and the period of the excitation. It seems you are being asked to measure the reciprocal of the frequency by tuning a string.