Coupled Oscillators: Part C (Swept Sine)

By:
S. A. Dodds
Physics Department
Rice University
Houston, TX

In this part we will use the function generator to excite the first oscillator with a sinusoidal wave and measure the response of the second oscillator. The scope is used to measure the voltage and hence infer the charge on capacitors Ca and Cb.

You can easily visualize what is happening by using the sweep function on the Agilent 33120A. Set the sweep start and stop frequencies with the SWEEP MENU.

In the Java example below, we have assumed the Agilent 33120A solution, with the function generator sweeping internally and the scope time base set to show one complete sweep.

This experiment requires a Java>-enabled Web Browser.

If an Agilent 33120A is not available, an alternate is to use a second function generator to sweep the driving frequency of a function generator that has an external sweep input. Set the second function generator for a triangle-wave output at 5-10 Hz and connect it to the VCF (voltage controlled frequency) input of the driving generator. Set the scope for X-Y operation, with the sweep voltage as X input and the capacitor voltage as Y input. If the driving generator is set near the resonance frequency you should see two peaks on the display. Adjust the amplitude and offset of the sweep generator and the scope scales to get a nice display.