A test instrument that displays a waveform is a(n):

A test instrument that displays a waveform is an oscilloscope. This device is specifically designed to visualize electrical signals, allowing users to see how the signal varies over time. The oscilloscope presents this information on a screen as a graphical representation, showing the voltage of the signal on the vertical axis and time on the horizontal axis.

This capability is essential for analyzing waveforms, such as sine waves, square waves, and complex signals, making it invaluable in the fields of engineering and electronics. Users can observe characteristics like amplitude, frequency, rise time, and distortion, which are critical for diagnosing issues in circuits and understanding signal behavior.

Other instruments like a function generator, ammeter, or multimeter serve different purposes. A function generator is used to create electrical waveforms, an ammeter measures current flow in a circuit, and a multimeter can measure various electrical properties like voltage, current, and resistance but does not display waveforms in real-time like an oscilloscope can. Therefore, the oscilloscope is the right choice for displaying waveforms.