A Smart Low-Cost QCM-D Based on Lightweight Frequency Domain Processing

This work presents an accurate low-cost smart measurement system capable of simultaneously monitoring the quartz crystal microbalance (QCM) series resonant frequency and dissipation factor with high accuracy, optimally adapting its settings to the operating conditions. The designed system is based on a microcontroller and is fully programmable and it exploits an ad hoc signal processing technique. The performance of the proposed measurement system was assessed experimentally using a prototype coupled with the quartz via an antenna pair, allowing noncontact measurements. Experimental results were obtained under different measurement conditions. The results demonstrated the effectiveness of the system, which is able to guarantee high-frequency accuracy even in the case of large mechanical loads, such as those that occur in in-liquid measurements. In liquid-loaded conditions, when working with transient response signals characterized by time constants as low as <inline-formula> <tex-math notation="LaTeX">$60 ~\mu \text{s}$ </tex-math></inline-formula>, a resolution of 10 Hz is found.