SISTEM PENGUKURAN IMPEDANSI BERBASIS FAST FOURIER TRANSFORM (FFT) DENGAN INTEGRASI REAL-TIME OPERATING SYSTEM (RTOS) PADA STM32

Wikan Jalu Komara, Prima Asmara Sejati, S.T., M.Eng., Ph.D.

2026 | Tugas Akhir | D4 Teknologi Rekayasa Instrumentasi dan Kontrol

Penelitian ini merancang dan mengimplementasikan sistem pengukuran impedansi secara kontinu dan real-time dengan mengintegrasikan algoritma Fast Fourier Transform (FFT) secara tertanam dengan Real-Time Operating System (RTOS) pada mikrokontroler STM32. Latar belakang penelitian ini didasari oleh kerentanan metode pengukuran impedansi domain waktu terhadap gangguan noise. Untuk mengatasinya, algoritma Fast Fourier Transform (FFT) diterapkan guna mengalihkan pemrosesan sinyal ke domain frekuensi demi meningkatkan akurasi. Namun, karena komputasi FFT ini sangat berat dan berisiko memicu kehilangan data (data loss), sistem operasi waktu-nyata (Real-Time Operating System/RTOS) diintegrasikan sebagai solusi komputasi paralel agar proses akuisisi sampel dan kalkulasi spektral dapat berjalan secara stabil sekaligus deterministik. Pengaruh penerapan arsitektur RTOS pada sistem memicu adanya beban tambahan (overhead) akibat interupsi manajemen kernel dalam mengelola tugas, yang berdampak pada peningkatan durasi waktu komputasi. Meskipun demikian, penurunan kecepatan eksekusi tersebut sangat minimal dan tidak mengganggu konsistensi nilai laju sampling ADC. Batas rentang frekuensi eksitasi (bandwidth) optimal yang dapat dicapai oleh sistem guna memperoleh hasil pengukuran dengan persentase error minimum berada pada rentang 100 Hz hingga 50 kHz dengan menggunakan konfigurasi jumlah sampel N=1024, di mana kualitas sinyal terbukti sangat konsisten pada nilai SNR more than 20. Pada pengujian frekuensi tinggi di atas 50 kHz sistem mulai berfluktuasi akibat efek kapasitansi parasitik serta mengalami penurunan kualitas total akibat limitasi fisik ADC dan gejala aliasing pada sinyal digital. 

This research designs and implements a continuous and real-time impedance measurement system by integrating the Fast Fourier Transform (FFT) algorithm embedded with the Real-Time Operating System (RTOS) on the STM32 microcontroller. The background of this research is based on the vulnerability of the time-domain impedance measurement method to noise interference. To overcome this, the Fast Fourier Transform (FFT) algorithm is applied to shift signal processing to the frequency domain to improve accuracy. However, because the FFT computation is very heavy and risks triggering data loss, a Real-Time Operating System (RTOS) is integrated as a parallel computing solution so that the sample acquisition process and spectral calculation can run stably and deterministically. The impact of implementing the RTOS architecture on the system triggers additional burden (overhead) due to kernel management interrupts in managing tasks, which has an impact on increasing the duration of computation time. However, the decrease in execution speed is very minimal and does not interfere with the consistency of the ADC sampling rate value. The optimal excitation frequency range (bandwidth) that can be achieved by the system to obtain measurement results with a minimum error percentage is in the range of 100 Hz to 50 kHz using a sample size configuration of N = 1024, where the signal quality is proven to be very consistent at an SNR value of more than 20. In high frequency testing above 50 kHz, the system begins to fluctuate due to the effects of parasitic capacitance and experiences a decrease in total quality due to physical limitations of the ADC and aliasing symptoms in digital signals.

Kata Kunci : Sistem Pengukuran Impedansi, ADC, Real-Time Operating System (RTOS), Fast Fourier Transform (FFT), STM32, Bandwidth, Signal-to-Noise Ratio (SNR), Jumlah Sampel.