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 HP 33120A. Set the sweep start and stop frequencies with
the SWEEP MENU.
In the Java example below, we have assumed the HP 33120A solution,
with the function generator sweeping internally and the scope time
base set to show one complete sweep.
Using your mouse, click on the instrument controls to adjust them.
If an HP 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.
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