Oscilloscopes: Seeing the Wave

A Multimeter tells you: “5 Volts.” But IS it 5 Volts? Or is it switching between 0V and 10V so fast that it averages to 5V? A Multimeter cannot tell. It is too slow. An Oscilloscope draws a graph of Voltage vs. Time.

The Square Wave (PWM)

Robots control motor speed using Pulse Width Modulation (PWM).

• 50% Speed: ON for 1ms. OFF for 1ms. Repeat.
• On a scope, this looks like a castle wall (Square Wave).
• If the “wall” is jittering left and right, your servo will shake.
• The scope lets you see the “Jitter” that is invisible to the naked eye.

The Noise Hunter

If your sensors go crazy when the motors turn on, check the scope. You will see “Spikes” of fuzzy noise riding on the clean line. That is electromagnetic interference. You need shielding. The Scope is the X-Ray machine of electronics.