Introduction

ELIA (Enhanced Lock-In Amplifier) ​​is a high-resolution acquisition system able to compensate for the random gain fluctuations of the analog-digital converter. When applied to a dual-channel lock-in amplifier, ELIA demonstrated a resolution enhancement of a factor 58 compared to a state-of-the-art commercial tool.

Technical features

The invention consists in a novel technique to compensate slow random fluctuations of the gain in a data acquisition chain based on an analog-to-digital converter (ADC). Examples of gain fluctuation sources are the ADC voltage reference or the low-frequency noise of components inside the ADC. The random fluctuation of the gain introduces an uncertainty in the conversion, which limits the smallest signal variation (resolution) detectable by the acquisition chain. The invention reduces the effect of these fluctuations thanks to a digital processing of the signals coming from two acquisition channels (not necessarily identical) which alternately acquire a reference signal and the signal under investigation. Differently from the conventional differential approach, this novel technique does not need the generation of a reference signal ideally identical to the signal to be measured, thus our device operates without calibration and without limitations over the working frequency span.

Possible Applications

• Electronic systems for high resolution measurements of slowly varying electrical signals or the amplitude of periodic or modulated electrical signals;
• Ultra-high resolution lock-in amplifiers for the measurement of amplitude variations less than one part per million.

Advantages

• ELIA allows to acquire electrical signals with higher resolution than the standard analog / digital acquisition scheme;
• Integrates seamlessly into any experimental setup: no calibration is required nor constraints of any kind are posed on the device under test;
• Minimal hardware / firmware impact on an existing dual-channel digital Lock-In Amplifiers.