IV. FUNCTIONAL TESTS AND DATA VISUALIZATION
Functional tests of the system and frequency measurements for each sensor were performed. In the FPGA device, there was only the measurement structure (i.e., the array of ring oscillators), no other structure was implemented. There were no other elements which could (intentionally or not) generate additional self-heating (idle mode). During the tests, the correctness of array and SPI register implementation was checked. Then, the commands for activity the chosen ring oscillator and data collection in Raspberry Pi were tested.