Lock-in amplifiers (LIA) are capable of measuring the amplitude and the phase of a signal relative to a defined reference signal, even if the signal is entirely buried in noise, it is vital important for extreme weak signal (e.g. 10 nV) detection. The lock-in detection technique is described both in the time and in the frequency domain.
It uses the knowledge about a signal’s time dependence to extract it from a noisy background, this method is termed demodulation or phase sensitive detection. A lock-in amplifier performs a multiplication of its input with a reference signal, also sometimes called heterodyne/homodyne detection, and then applies an adjustable low-pass filter to the result. LIA looks like a extreme sharp bandpass filter, the Q value up to 10^6, so it is easy to isolate the signal at the frequency of interest from all other frequency components.
Home-built softwave digital lock-in amplifier
Frequency range: below 20 kHz (dependent on the speed of ADC )
Linear range: 1 μV to 10 V; Noise level: 0.6 μV
Home-built Analog lock-in amplifier module
Frequency range: 300 kHz to 40 MHz
Linear range: 10 μV to 300mV; Noise level: 4 μV
(This range will be extended by extra gain or attenuation)
High sensitivity CE-C4D detection with home-built Analog lock-in amplifier module
eDAQ vs Home-built instrument
Update time: 2021-11-18