The trace looks wrong

A flat line

• Check the jumper or signal is on the board’s input pin, and the grounds are joined.
• The trace may be off screen: press Autoset.

The trace jumps about

• The trigger level is probably outside the signal. Press Autoset, or move the Trigger level into the middle of the wave.
• With Normal mode, a signal that rarely crosses the level updates rarely. Switch to Auto.
• The strip above the screen says Triggered, Not triggered or Waiting for a trigger; see Trigger.

Part of the screen is hatched

A capture holds less signal than the screen shows, so part of the screen has no samples. The note under the measurements says why:

• With the rate set by hand (Manual), choose Auto under Rate setting, or lower the rate or the time per division.
• In Auto, either the board’s longest capture is too short for this time per division, or a lower rate would show the signal falsely. A shorter time per division fills the screen.

See Rate setting.

The wave is slower than it should be

The signal may be faster than half the sample rate, so it appears as a false, slower wave. With the Alias check on, the scope says so and gives the likely true frequency. Raise the Sample rate above twice that. See Sampling.

A fast wave looks jagged, or swells and shrinks

With few samples in each cycle, joining them with straight lines draws shapes that are not in the signal: a jagged pattern, or a slow swelling “beat”. Keep Drawing on Sin(x)/x (under Display): it draws a sine truly down to 2.5 samples a cycle. Closer to half the sample rate, or for a square wave, raise the rate. See Drawing.

The numbers jump

Noise on the signal moves the readings. Join the grounds with a short wire, keep the input wire short, and keep it away from mains cables and motors.