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Direct Comparison of Analogue and Digital FGPA-Based Approaches to Synchronous Detection

Teren O., Tomlain J., Sedlacek R.

Metrology and Measurement Systems

2018

Vol. 25, nr 1

57--69

This paper deals with a comparison between digital and analogue implementation of a synchronous detection algorithm. The commonly used implementation methods of synchronous detection are presented in the paper. The paper describes FPGA-based digital and analogue hardware approaches, focusing on the digital design. The characteristics of used analogue-to-digital converters are measured. Both proposed approaches are directly compared in terms of sensitivity and long-term stability. The achieved results, along with identified limitations and proposed improvements are widely discussed.

The implementation and the performance analysis of the multi-channel software-based lock-in amplifier for the stiffness mapping with atomic force microscope (AFM)

Sikora A., Bednarz Ł.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2012

Vol. 60, nr 1

83-88

In this paper the implementation of the surface stiffness mapping method with the dynamic measurement mode of atomic force microscopy (AFM) is presented. As the measurement of the higher harmonics of the cantilever’s torsional bending signal is performed, we are able to visualize non-homogeneities of the surface stiffness. In order to provide signal processing with the desired sensitivity and selectivity, the lock-in amplifier-based solution is necessary. Due to the presence of several useful frequencies in the signal, the utilization of several simultaneously processing channels is required. Therefore the eight-channel software-based device was implemented. As the developed solution must be synchronized with the AFM controller during the scanning procedure, the real-time processing regime of the software is essential. We present the results of mapping the surface stiffness and the performance tests results for different working conditions of the developed setup.