A FPGA-based frequency measurement system for high-accuracy QCM sensors

This paper proposes the design and implementation of a FPGA-based frequency measurement system for Quartz Crystal Microbalance (QCM) sensors. Using different design techniques a bandwidth of 40 MHz and a resolution of 0,05Hz is achieved. This work is part of a bigger project focused on the development of a standalone QCM system for the analysis and characterization of different paints. Two methods are used to implement the digital counter, the direct frequency measurement and the delay lines. Special attention is paid in the design of the time-base generator. Measurement errors due to the drift of the system oscillator are discussed, and several solutions are proposed taking advantage of the embedded DLL circuits available in the FPGAs. The designed digital counter is implemented and tested using the Xilinx’s Spartan XC3S200 FPGA.