Lock-in amplifiers are key devices in numerous instruments used in the optical sciences and in optical equipment in industry. In many experimental configurations, they represent the means to reliably detect and record very small signals that are superimposed by noise.
The purpose of this text is to provide a step-by-step introduction to the technique of phase-sensitive detection using lock-in amplifiers, and to provide examples of its applications in optical instruments. The book begins by explaining the basics of how modulation is used to extract a signal from noise. Different types of modulation are discussed in detail and are compared. The book then presents the various applications of lock-in amplifiers in optical instruments, and the focus shifts from electronics to optics.
Some of the covered optical applications of lock-in amplifiers are optical spectroscopy, including absorption spectroscopy, fluorescence spectroscopy, and phosphorescence spectroscopy; optical interferometry, including detailed presentations of the various spectrometers used with lock-in amplifiers; crystal research and technology, including explanations of magneto-optical, electromechanical, and electro-optical effects; infrared thermography; laser wavelength stabilization; and advanced microscopy.
The book is intended for readers who want to better understand instruments and experiments based on lock-in detection and/or to design (and perform) new experiments in which lock-in amplifiers are applied.
Battery Cell Management Unit (CMU)
SENSIPLUS is a device integrating precision analytics with heterogeneous multi-sensors in a single microchip of 3x3mm size at 2mW power. It is the first to include a comprehensive Wideband Electrochemical Spectrometer with Lock-In Amplifier, a Potentiostat and sensors for Temperature, Relative Humidity and Gassing. Impedance Spectra measurements enable improved estimation of the cell State of Charge, State of Health, State of Function and State of Power (SoX). SENSIPLUS off-chip interface supports strain, pressure and liquid leakage sensors. Multi-sensor measurements are cross-correlated with an internal configurable Deep Learning Inference Accelerator to stream minimal data to the Battery Management System.
The CMU exploits SENSIPLUS’ electrochemical measurements to analyze from outside the relevant chemical, physical process inside the cell, the anode and cathode integrity while monitoring safety, during battery operation. Data supplied to the Battery Management System helps controlling Cell Balancing and to direct electrochemical stimula aiding cells healing.
SENSIPLUS also includes a multi-drop single wire High Voltage isolated bus to chain multiple cells to the BMS or it can be used with an external chip in a Smart Mesh wireless configuration for increased safety and flexibility.
The CMU is chemistry independent and it can be used with Li-ION and Li-Fe-PO4 battery packs, similarly it can be applied to 3b generation of LNMO cells, Supercapacitors and Fuel Cells combinations.
Structural Integrity, Corrosion Monitoring
Electrochemical methods are among the most effective and commonly used to monitor the progressing of corrosion in infrastructures.
The corrosion mechanism taking place in an aqueous or vapor phase is electrochemical in nature. The electrochemical signal is one of the primary sources of information that relates to behavior in potential, current, and electrical charge of a corroding specimen. It arises from processes that cause corrosion and other electrochemical reactions. When applied online for monitoring in-situ uniform, localized, galvanic, or more forms of corrosion, electrochemical techniques are very convenient means to measure corrosion rate of materials.
The SENSIPLUS microchip once configured with three electrode potentiostatic measurement can be used for online monitoring of the linear polarization resistance (LPR), an indicator of the corrosion trend, or it can forecast corrosion by electrochemical impedance spectroscopy (EIS), while the rate of corrosion is best assessed using harmonic distortion analysis (HDA), which is also supported by SENSIPLUS with its capability to demodulate the 2nd and 3rd harmonic of the applied sinewave.
Concurrently SENSIPLUS will sense relevant environmental parameters such Temperature, Moisture, pH or Relative Humidity to improve the corrosion indicators.