ABSTRACT
In this chapter, the author uses octave to postprocess and Fourier-transform the samples. Besides using octave, he also makes the data available to Experimental Physics and Instrumental Control System (EPICS), such that the standard EPICS programs for display and post-processing can be used. Recording waveforms in octave and processing them further is convenient to produce plots of the spectra, but if the author wants to include the geophones in their EPICS control system, he needs to provide the database and prototype files. For the sensor node, the authors use the NodeMCU microcontroller and the Ticker.h library that allows sampling with a rate of 1000 times per second. After the signal from the geophone is amplified, they use the analog-to-digital converters on the NodeMCU microcontroller and collect 1024 samples: one sample every millisecond, and then pass the digitized samples to the host computer via WLAN.
