The first component of the meter is a sine wave oscillator. There are several ways to generate a sine wave; the most common are:
- A Wein bridge oscillator
- A phase shift oscillator (either buffered or unbuffered)
- A Bubba oscillator
- A quadrature oscillator
- A digital synthesizer (such as AD9833)
I've found the following references particularly useful:
Right now I'm currently evaluating the different oscillators, mostly based on price and distortion.