Altro VERIFICATO
Pt 100
Università degli Studi di Roma - La Sapienza ingegneria energetica Curriculum ingegneria energetica (percorso valido anche ai fini del conseguimento del doppio titolo italo-venezuelano) 2018
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- A digital instrument was designed using LabView for precise temperature measurement from a Pt100 sensor.
- The system incorporates a conditioning circuit (quarter deflection bridge and differential amplifier) to convert the sensor's resistance change into an analog voltage signal.
- A National Instruments data acquisition card (DAQ) with 16-bit precision (0-100°C range, 61.2µV resolution) is used for Analog-to-Digital Conversion (ADC).
- Digital Signal Processing (DSP) is applied to enhance signal manageability and information extraction.
- The Pt100 sensor's temperature-resistance relationship (quadratic) introduces non-linearity, which is corrected using a cascade linearization algorithm. The 'exact' inverse function was chosen over an approximation due to better accuracy at higher temperatures.
- An Anti-Aliasing Filter is crucial before ADC to prevent information loss due to sampling frequencies below the Nyquist-Shannon threshold.
- A second-order Butterworth low-pass digital filter was implemented via bilinear transformation to remove specific frequency-controlled noise.
- The filter coefficients were determined for a cut-off frequency of 15Hz and a sampling rate of 200Hz, chosen to balance accuracy with the slow-changing nature of temperature.
- A virtual instrument (VI) in LabView provides a user-friendly interface for simulating temperature signals, injecting noise, applying DSP, and saving processed data in '.csv' format.
- The efficacy of the filter is demonstrated through spectral analysis (Fourier Transform, DFT, FFT), showing significant attenuation of noise components (e.g., near 50Hz).
- Key advantages of DSP include independence from physical component aging, while a disadvantage is information loss due to signal discretization.
- The overall system successfully linearizes the sensor output and effectively reduces noise, achieving high measurement fidelity.