Andrew J. Harvie and John C. de Mello created OLIA, an open-source digital lock-in amplifier. Digital lock-in is a method for isolating weak signals to facilitate measurement amongst background noise, which is processed away via digital signal processing (DSP). The Open Lock-In Amplifier (OLIA) is a Teensy 4.0-based system that can outperform far more expensive commercial devices.

https://www.pjrc.com/olia-open-source-digital-lock-in-amplifier/