Lock-in amplifier error prediction and correction in frequency sweep measurements

Area of Science:

• Electrical Engineering
• Measurement Science
• Signal Processing

Background:

• Lock-in amplifiers (LIAs) are crucial for precise measurements, but errors arise with time-varying reference frequencies.
• Frequency response measurements often involve sweeping the reference frequency, introducing potential inaccuracies.
• Existing methods may not fully account for the dynamic interplay between sweep speed, filter characteristics, and system response.

Purpose of the Study:

• To develop an analytical algorithm for predicting measurement errors in LIAs operating with swept reference frequencies.
• To present a straightforward method for correcting these identified errors.
• To validate the proposed algorithm and correction technique through rigorous analysis and experimental data.

Main Methods:

• An analytical algorithm based on the final value theorem of Laplace transforms was developed for error prediction.
• A novel error correction method utilizing a double-sweep measurement strategy was implemented.
• Mathematical analysis was performed and corroborated by computational simulations and experimental validation.

Main Results:

• The proposed algorithm accurately predicts errors caused by frequency sweeps in LIAs.
• The double-sweep correction method effectively mitigates the identified measurement errors.
• Validation confirmed the algorithm's and method's efficacy across simulations and real-world measurements.

Conclusions:

• The developed analytical algorithm provides a reliable means to predict LIA errors during frequency sweeps.
• The presented double-sweep technique offers a practical solution for correcting these errors, improving measurement accuracy.
• This work advances the precision of frequency response measurements using lock-in amplifiers with dynamic reference frequencies.