70009 Parallax Inc, 70009 Datasheet - Page 52

• Manufacturer Part Number: 70009
• Description: BOOK UNDERSTANDING SIGNALS
• Manufacturer: Parallax Inc
• Type: Signal Analysisr

Specifications of 70009

• Style: Book
• Title: Understanding Signals
• Contents: Guide to Generate, View and Measure Wave Forms
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Other names: 70009PAR

Dual Sine Waves with the DualSineWaves.bs2 Program
You will again reuse the circuit from the previous two activities.
' Understanding Signals - DualSineWaves.bs2
' Send two size waves to the piezo speaker using the FREQOUT command
'{$STAMP BS2}
'{$PBASIC 2.5}
DO
LOOP
You should see an unusual signal like the one shown in Figure 3-10. This repetitive
signal is composed of the 2 kHz and 6 kHz sine waves mixed together.
The 2 kHz component is easily discernible as you can measure from peak to peak of the
mixed signal. The 6 kHz component is also visible as the smaller curves at the top and
sides of each wave.
FREQOUT 9,10000,2000,6000
√
√
√
√
Set the Vertical dial to 1 V/division and the Horizontal dial to 200 µs.
Run the program DualSineWaves.bs2.
Set the Cursor Settings switches to Vertical Bars and Floating .
Carefully measure 2 kHz and 6 kHz signal components.
Why does my signal look different if I change the capacitor value? The RC network
that converts the digital pulses sent by the BASIC Stamp’s
waves does two things: 1) reduces the amplitude of the sine wave, called signal attenuation,
and 2) moves the sine wave to the right, which is called a phase shift. The resulting sine
wave’s amplitude and phase shift is a function of RxC and of the frequency of the sine wave.
When
attenuated and phase shifted separately by the RC circuit. If you change the value of C in
RxC, the overall shape of the signal changes because the component sine waves are
attenuated and phase shifted differently. If you complete this activity with a different value
capacitor and your resulting waveform differs form the one below, you can still use the FFT
function to measure that the same component frequencies are present.
FREQOUT
sends two different frequencies at once, each component sine wave is
FREQOUT
command into sine