Novel Digital Lock-in Amplifier Algorithm Independent of Low-Pass Filter with Low SNR Performance

Lock-in amplifiers are key components in many applications that require high resolution sensing. Aiming at the problem that the signal-to-noise ratio performance of traditional lock-in amplifier highly depends on the low-pass filters, this paper introduces the algorithm realization and verification process of a new digital lock-in amplifier. The algorithm is independent of the filter, and the theoretical SNR reaches -141.82 with the accuracy of 95%. In this work, a novel digital lock-in amplifier algorithm is based on a time analysis method, which is recommended for bearing fault detection. In order to verify the effectiveness of the proposed technique, numerical simulation and experiments have been carried out to verify the proposed algorithm and its great potential in weak signal processing applications. It has been proved that this new lock-in amplifier algorithm has higher universality and better anti-noise ability compared with the traditional algorithm.

I. Introduction

Vibration analysis is widely used in health monitoring. One of the main problems encountered in this process is the existence of complex background electrical noise, thus the sensor output signal is polluted [1]. In extreme cases, when the sensor output level is very low compared to the noise level, the weak signal will be highly contaminated. This phenomenon distorts the measurement results and leads to the failure of the processing capability of the monitoring system.