Telemetric QCM-D based sensing system with adaptive excitation frequency

The use of contactless sensing systems represents a measurement technique of great potentiality in the development of engineering systems that have to face specific challenges related to hazardous or critical measurement environment. In this paper a telemetric sensing system for QCM sensors is proposed. The system is based on air coupled antennas, a timed excitation, and an optimized readout circuit, properly designed to avoid disruptive loading of the resonant system. The measurement strategy involves the excitation of the quartz with a sine burst and the acquisition of the transient response after the end of the excitation phase. The excitation system implements a strategy for the optimal excitation frequency search, which allows for the estimation of the resonance frequency of the QCM in the different operating conditions also in the presence of large mechanical loads as it occurs in in-liquid measurements. In this way the resonant electromechanical system is forced to operate close to its optimum working point with the maximum signal-to-noise ratio and preserve the typical high performance of QCM based monitoring systems in terms of sensitivity and frequency stability.