Rancang Bangun Alat Ukur Kadar Air Agregat Halus dalam Pengujian Material Dasar Beton Berbasis Mikrokontroler ATmega8535 dengan Metode Resistif
DOI:
https://doi.org/10.25077/jfu.2.4.%25p.2013Abstract
Telah dilakukan rancang-bangun sistem alat ukur kadar air agregat halus berbasis mikrokontroler ATmega8535 dalam pengujian material dasar beton menggunakan metode resistif.  Selama ini, penentuan kadar air tersebut dilakukan secara manual yaitu dengan cara menimbang berat awal dan berat akhir agregat.  Selisih kedua berat tersebut dibagi dengan berat akhir, hasilnya dikali 100% untuk mendapatkan kadar air agregat.  Berat awal agregat adalah berat sebelum agregat dikeringkan, dan berat akhir adalah berat pada saat agregat tidak mengandung air.  Agregat kering (kondisi akhir agregat) didapatkan dengan cara memanaskan agregat di dalam oven dengan temperatur 100oC±5oC. Agregat halus ditempatkan di dalam sebuah kotak dengan ukuran 10  x 10  x 5 cm3, dimana kedua sisi bagian dalam kotak adalah material konduktor yang terbuat dari logam (plat PCB). Berdasarkan pengujian awal, resistansi agregat bervariasi terhadap kadar airnya. Berdasarkan hasil ini, perubahan resistansi dikonversi menjadi perubahan tegangan menggunakan rangkaian pembagi tegangan.  Keluaran rangkaian ini kemudian dikondisikan agar bisa diproses oleh mikrokontroler ATmega8535. Berat sampel yang digunakan adalah 500 g, dan variasi waktu pemanasan sampel adalah 15 jam, 18 jam, 21 jam, 24 jam dan 27 jam.  Pengujian akhir menunjukkan bahwa alat yang dirancang ini dapat digunakan untuk mengukur kadar air agregat halus. Alat ini mempunyai sensitivitas 4,6 V/% kadar air, akurasi sebesar 93%, dan kesalahan sebesar 5,1%.Downloads
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