Temperature measurement is one of the important parameters in guaranteeing the quality of a product. Thermometer accuracy quality assurance is very important and crucial in the production process. Thermometer accuracy requires traceability to international standard units of measurement through a routine calibration process. The method of calibration of the thermometer uses a temperature controlled chamber/bath and requires high temperature stability. Chambers/baths on the market are relatively expensive and the temperature calibration process takes a long time because at each set point stability must be waited. In this study, the thermometer calibration was carried out by comparing the readings of the calibrated thermometer with a standard thermometer and using a calibration regression equation to determine the value of the standard error of estimate (SEE). The regression equations use inverse and classical methods, each with linear equations, polynomial equations and power equations. From the research that has been done, the digital thermometer calibration can be done by using a temperature-controlled bath that is only by comparing the readings between a standard thermometer and a calibrated thermometer by recording any temperature increases. To evaluate the uncertainty of the digital thermometer calibration, the smallest SEE value is obtained in the power equation, namely 0.001. There were no significant differences in each type of regression and the combined standard uncertainty results were 0.16 at 37 °C using linear regression.

Optical plethysmography technology has been used to design and develop a portable device for heart rate sensor. These device, consisting of near-infrared light-emitting diodes (LEDs) and photodetectors, offer a simple means of extraction the heart rate noninvasively on fingertip’s healthy volunteers. The acquisition signal is carried out based on the detection of the absorbance of near-infrared light in blood vessels due to heart’s pump activity. The microcontroller is used as the main component of electronics module. The communication to personal computer (PC) and power supply of device are provided by USB system. The algorithm of Fast Fourier Transform (FFT) in the software was used to generate the spectra of the signal and determine the HR of the obtained signal. The performance of developed device is tested on 10 fingertips of healthy volunteers, aged 19 to 57 years. A Pulse Oximeter commercial was used as gold standard instrument for comparison of results obtained by the designed device. In this paper the correlation analysis was applied to validate the results of both devices. The analysis show that the HR measured is positively correlated. These results show that the correlation between the HR measured by both the designed PPG device and Pulse Oximeter commercial are almost perfectly linear. Thus, the pulse signals gathered by the designed device are accurately believed to be representative of the heart activity of healthy volunteers. The validation method supports that designed device can potentially be developed as a simple, low power, and portable device for the importance of biomedical research (mainly for processing biomedical signal) and clinical practices.

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1 Pusat Studi Fisika Terapan (Pusfit) dan Program Studi Fisika Universitas Ahmad Dahlan Yogyakarta 2 Pusat Studi Fisika Terapan (Pusfit) dan Program Studi Pendidikan Fisika Universitas Ahmad Dahlan Yogyakarta Abstrak Simulasi dari skema pengukuran perubahan frekuensi Doppler ultrasonik telah ditunjukkan. Skema ini digunakan untuk mendeteksi kelajuan dari suatu benda yang sedang bergerak. Sinyal gelombang ultrasonik ditimpakan pada benda yang sedang bergerak dan sinyal yang terpantul kemudian diolah untuk mengidentifikasi spektrum perubahan frekuensi Doppler ultrasoniknya dengan menggunakan algoritma FFT (Fast Fourier Transform). Sebagai parameter masukan adalah frekuensi transmiter, frekuensi sampling, kecepatan ultrasonik, kelajuan obyek dan sudut efektif antara berkas ultrasonik dengan lintasan linear gerak obyek. Implementasi simulasi dilakukan dengan MATLAB berbasis GUI (Graphical User Interface). Hasil simulasi menunjukkan bahwa dengan frekuensi transmiter 200 kHz dan kelajuan obyek sekitar 144 km/jam dalam bidang transportasi, spektrum perubahan frekuensi Doppler ultrasonik nampak jelas dan nilai terukurnya sekitar 38 kHz. Namun, dalam bidang medis untuk pengukuran akelajuan aliran darah dengan frekuensi transmiter 10 MHz dan kelajuan benda 7 m/s, spektrum beda frekuensi Doppler ultrasonik tidak begitu jelas tetapi nilai terukurnya sekitar 73,54 kHz. Kata Kunci: perubahan FREKUENSI Doppler ultrasonik, algoritma FFTAbstract A simulation of Doppler ultrasound frequency shift measuring scheme has been introduced to detect on speed of the a moving object. The ultrasound signal was impinged onto the a moving object and the reflected signal was processed by a FFT algorithm to identify the spectrum of Doppler ultrasound frequency shift. As the input parameters are the transmitter of frequency, sampling of frequency, velocity of ultrasound, speed of object and effective of angle between the beam of ultrasound and the linear path of a moving object. This simulation was implemented by MATLAB based on GUI (Graphical User Interface). The result of simulation showed that the spectrum of Doppler frequency has been obviously shifted at the 200 kHz of transmitter frequency and 144 km/h of speed object (transportation field), and the its measured value is about 38 kHz. However, in the medical field, it has been not obviously shifted at 1 MHz of transmitter frequency and 7 m/s of speed object (blood flow), but the its measured value is about 73,54 kHz. Key Word: Doppler ultrasound frequency shift, FFT algorithm PENDAHULUANSalah satu keunggulan dalam pengukuran fisis benda adalah pengembangan suatu sistem deteksi yang tak merusak (non destructive) dan tak kontak (contactless) dengan benda. Dalam bidang perminyakan, misalnya, metode ini digunakan untuk mendeteksi kebocoran pipa yang terpendam dengan tanpa membongkarnya [1]. Sistem deteksi yang demikian ini, menjadi sangat penting dalam dunia medis. Proses diagnosis dan monitoring suatu penyakit sangat membutuhkan metode yang tidak membawa dampak samping (tak merusak) bagi pasi...