Construction of a Low-Cost Lock-in Amplifier for Physics Experiments in Undergraduate Laboratory

Abstract

This research presents the design and construction of a cost-effective, dual-phase lock-in amplifier with a simplified architecture that is well-suited for undergraduate physics laboratory experiments. Its core circuitry comprises a pre-amplifier, a phase-shifting circuit, and a fourth-order, active, low-pass filter, utilizing the AD630 IC as the primary phase-sensitive detector. The control system incorporates an Arduino UNO R3 microcontroller and an LCD display. Performance was evaluated by measuring the resonant frequency of a series RLC circuit using two resistor values (30 Ω and 100 Ω). Experimental results demonstrated high accuracy: the measured frequency deviated by less than 2% from the theoretical values, and the phase angle error was only 0.02%. This highlights the developed circuit's precision and efficiency, making it applicable for small-signal research. Furthermore, its cost-effectiveness and modifiable design render it an ideal educational tool for university physics laboratories and for low-noise-signal measurement applications in industrial settings.