ENPh257: Thermodynamics 3T: Data Acquisition

TMP36 temperature sensor Output 0 – 5 V Nominal conversion factor of 10 mV/◦C Nominal accuracy ±1 K at room temperature Can be calibrated to much better than that! Simple test: put six together and compare outputs Absolute temperature not as important as differences. © Chris Waltham, UBC Physics & Astronomy, 2017

Arduino ADC The Arduino board has a 10-bit analog-digital converter (ADC) to read the TMP36 o/p. 210 = 1024 possible outputs 0 – 5V Steps = 5 mV Equivalent to 0.5 K This is an ADC limitation rather than a sensor limitation. Can improve if desired by amplification for a restricted temperature range, to avoid big steps in the data: © Chris Waltham, UBC Physics & Astronomy, 2017

Matlab code © Chris Waltham, UBC Physics & Astronomy, 2017

Finessing the code Record raw output voltages: allows later recalibration Save data as experiment proceeds. Don’t leave the data write statement to the end of a long run, only to have a crash with the loss of all data. Have an automatic date/time stamp in your data filename – saves accidental erasure of previous, good data. For example: c0 = clock; t0 = 3600*c0(4)+60*c0(5)+c0(6); % time in minutes ts = datetime('now'); DateString = datestr(ts,30); filename = [‘Al-rod_5W_20s_period' DateString '.xlsx']; Saving data to an excel file allows easy checking and annotation. Read back into MATLAB to make publication-quality graphs. © Chris Waltham, UBC Physics & Astronomy, 2017