What is a function/waveform generator?

A function generator is an electronic test device that generates a variety of standard waveforms for a device under test (DUT), such as sine, square, ramp, or sawtooth waveforms. In circuit design and circuit boards, testing often requires the use of controlled signals to simulate routine operations. Testing physical systems and sensors often requires stable and reliable signals that are as low as a few microvolts and may be as high as tens of volts or more.

By providing an excitation signal or a known input signal, we are able to observe how the device responds under different conditions. Does the device under test exhibit the expected characteristics? What kind of tolerance does it have before the performance breaks down?

You can evaluate the performance of the device under test by feeding a known normal signal into the device and monitoring the output. The output of the waveform generator must be pure and stable, and should be representative of the true signal that will be used by the device's final application.