2.5 Non-sinusoidal signals

I declare: solidlikelyshaky

1. Describe a square wave by its frequency and duty cycle, and explain what PWM controls in a motor or an LED.
2. Explain in one sentence why a square wave contains odd harmonics and what that does to long wires.
3. Measure a signal’s rise time and say what the probe adds to it.
4. Recognize supply noise, contact bounce and crosstalk on the oscilloscope, and tell them apart.
5. Explain signal-to-noise ratio and measure the noise floor of a measurement chain, input shorted.
6. Diagnosis: a PWM-driven motor that sings, relate the note heard to the switching frequency and say what to change.