1. ENPh257: Thermodynamics
3T: Data Acquisition

2. 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

3. 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

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

5. 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