STUDI KARAKTERISTIK SISTEM STANDAR TEGANGAN DC
T 621.319 12 KIM
ABSTRAK
Noise frekuensi rendah dan perubahan temperatur ruang pada sistem standar tegangan dc mempengaruhi stabilitas tegangan dc yang tentunya mempengaruhi akurasi dan ketidakpastian nilai standar tersebut. Dengan demikian karakterisasi noise dari sistem standar tegangan dc serta karakterisasi temperatur dari sel standar elektronik dc sangat diperlukan dalam optimasi perencanaan dari sistem standar tegangan dc yang akurat dan stabil. Penelitian ini bertujuan untuk dapat mengurai atau mengidentifikasi karakteristik noise dan mengetahui level noise pada frekuensi rendah dari sistem standar tegangan dc, dengan menggunakan metode statistik variansi Allan dua-sample (dalam domain waktu) dan analisis power spectral density (dalam domain frekuensi). Selain itu untuk mengetahui karakteristik tegangan keluaran fungsi temperatur dari sel standar elektronik dc. Telah dilakukan karakterisasi noise terhadap sistem standar tegangan dc yang terdiri dari sel standar dc, scanner, nanovoltmeter, serta perkawatannya dengan metoda statistik variansi Allan dua-sample dan power spectral density (fast fourier transform). Dari hasil analisis ( karakterisasi) diperoleh bahwa sel standar elektronik dc (22, 24 nV) mempunyai noise floor yang lebih tinggi dibanding dengan sel standar dc kimia I sel Weston (8,04 nV). Untuk karakterisasi tegangan keluaran fungsi temperatur set standar elektronik Cropico 1,018 volt digunakan pengontrol temperatur thermo element untuk mengatur temperatur box aluminium luar set standar dari 20 sampai dengan 34 °C. Karakteristik temperatur sel standar elektronik dc diperoleh dengan persamaan ketergantungan tegangan terhadap temperatur: VO1 r = 1,018 803 25 V + (0,425.T – 0,0295.T2) µV, dengan kesalahan curve fitting n,aksimum 0,65 µV. Dari basil analisis noise pengaruh temperatur, diperoleh kondisi level noise floor rendah pada saat temperatur box mendekati homogen. Kata Kunci: standar tegangan dc, noise, temperatur, variansi Allan dua-sample, power spectral density. iv
ABSTR4CT
Low frequency noise and room temperature fluctuation at the dc voltage standard system influence dc voltage stability which then degrade the accuracy and uncertainty on the standard value. Therefore noise characterization of the dc voltage standard system and temperature characterization of the dc electronics standard cell are very important in the design optimization for an accurate and stable dc voltage standard system. The objective of the study was to finely identificate noise characteristics and to obtain noise level at low frequency of the dc voltage standard system, use two-sample Allan variance statistic method (in time domain) and power spectral density analysis (in frequency domain). Also to observe the temperature influence on the output voltage characteristic of the dc electronics standard cell. The noise characterization of the dc voltage standard system namely: dc standard cell, scanner, nanovoltmeter, and wiring were performed by using two methods each twosample Allan variance (statistic) and power spectral density ( fast fourier transform). From the analysis (characterization) were found the noise floor level of the dc electronics standard cell (22.24 n I i s higher than its chemical dc standard cell / Weston cell (8.04 n For the output voltage characterization of the electronics standard cell Cropico 1.018 volt as temperature function was used thermo element temperature controller to adjust the aluminium box temperature of the electronics standard cell from 20 to 34 °C. Temperature characteristics of the dc electronics standard cell was found fit to the temperature dependence: ` L our = 1.018 803 25 V + (0.425.7' – 0.0295. T ) µ I with maximum curve fitting error 0.65,uV The analysis of the influenced temperature noise shows a condition, which has low noise floor level, when the box temperature approximately homogen. Key Words: dc voltage standard, noise, temperature, Allan variance, power spectral density.
V
