Constructing Prototype Lock-in Amplifier with LabVIEW & DAQ

Xiaoyu Wu08300290011

Dept. of Physics, Fudan University

What is Lock-in Amplifier(LIA)?

• Detect & Measure Signals• Even with overwhelming noise• Typical S/N ratio -60dB

Signal + Noise

Amplitude + Phase as DC

Typical Application: Scanning Tunneling Spectroscopy

Principle of LIA

• Phase Sensitive Detection• Orthogonality of Sinusoidal Functions

LOW-PASS FILTER

LabVIEW & DAQ

Realizing the Algorithm

Demonstration

Features

• Signal Frequency: ~Hz to ~kHz• Signal Amplitude: 0.005V tested• Sampling Rate: maximum 50kHz, 40kHz tested

Drawbacks

• S/N Ratio• Function Generator