Design of a Cost-Effective Analog Lock-In Amplifier Using Phase Sensitive Detector

The measurement of a physical quantity in the presence of noise is a typical situation in research science. A lock-in amplifier is an electronic measurement device which has the capability of detecting, amplifying, extracting and measuring small signals buried within noise sources. This noise source can typically be thousands of times greater than the original signal. This paper details the procedure of building a simple and cost-effective analog lock-in amplifier. Some approaches have been investigated in designing this lock-in amplifier, taking into consideration the efficiency, expense, and practicality of the design. The final design is simulated in NI Multisim program and then executed in a practical circuit using basic, inexpensive electronic components. Using the essential technique of phase sensitive detection, the lock-in amplifier can provide extensive improvements on the signal-to-noise ratio. The simulation output presents very accurate results showing the functionality of the lock-in amplifier. The practical output also shows a compelling result with the presence of minor fluctuations in the amplitude of the signal.