Can the Lock-in Amplifier demodulate using an external source?
Yes.
Moku:Lab's Lock-in Amplifier supports direct demodulation with an external source, demodulation with a PLL (phase-locked loop) locked to an external source, and the ability to modulate and demodulate at different frequencies.
To change the demodulation signal source, tap the Configuration icon on the top right corner and select from "Local oscillator source" menu.