Lock-in amplifier principle

Basic principles In essence, a lock-in amplifier takes the input signal, multiplies it by the reference signal (either provided from the internal oscillator or an external source, and can be sinusoidal or square wave), and integrates it over a specified time, usually on the order of milliseconds to a few seconds.

1. How do lock-in amplifiers work?
2. What is lock-in technique?
3. What is the purpose for dual phase lock-in amplifier?
4. How does a phase sensitive detector work?

How do lock-in amplifiers work?

Lock-in amplifiers use a technique known as phase sensitive detection to single out the component of the signal at a specific frequency and phase. Once it does this, noise signals at other frequencies or random phases are rejected through electronic (analog lock- in) or software (DSP lock-in) filtering.

What is lock-in technique?

The lock-in technique is an AC modulation technique used to detect small AC signals hidden in a noisy environment. Multiplication of the measurement signal by the reference signal results in a DC component proportional to the amplitude of the measured signal at the modulation frequency.

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.

How does a phase sensitive detector work?

A lock-in, or phase-sensitive, amplifier is simply a fancy AC voltmeter. Along with the input, one supplies it with a periodic reference signal. The amplifier then responds only to the portion of the input signal that occurs at the reference frequency with a fixed phase relationship.