What advantage do lock-in amplifiers give over doing an FFT and looking at the frequency spectrum?

1. What is the purpose of lock-in amplifier?
2. How does lock-in detection work?
3. What is the purpose for dual phase lock-in amplifier?

What is the purpose of lock-in amplifier?

Lock-in amplifiers are used to detect and measure very small AC signalsall the way down to a few nanovolts. Accurate measurements may be made even when the small signal is obscured by noise sources many thousands of times larger.

How does lock-in detection work?

They employ a homodyne detection scheme and low-pass filtering to measure a signal's amplitude and phase relative to a periodic reference. A lock-in measurement extracts signals in a defined frequency band around the reference frequency, efficiently rejecting all other frequency components.

What is the purpose for dual phase lock-in amplifier?

A complete digital dual-phase lock-in amplifier system based on DSP and LabVIEW was designed. It can extract the weak sinusoidal signals submerged by noise. This design has the advantages of high accuracy, low cost and portability, and its update and transplantation are easy.