Test Result
For our system testing, we followed a systematic process to test the functionality after we received the chip and PCB from foundries. First, after we received the PCB, we soldered the infrared LED and photoresistor to make sure we can get a clear input signal, then we adjusted the variable resistor (potentiometers) to make sure we can get desired DC supply voltage and all the voltage regulators can provide accurate and stable voltage for our chip, it is tested on the PCB without the chip soldered on. Then we soldered all the off-chip resistors, capacitors, Arduino, and LCD screen. After making sure all the DC points are working accurately and input signal can be captured, we placed our chip on PCB and tested each OTA and Comparator step by step to verify all component are working as we desired.
We applied real signal which acquired by our LTR-4206E sensor. Figure 14 to 16 respectively shows the input signal, output signal of Heart rate OTA1, output signal of Heart rate OTA2, output signal of Heart rate comparator. In each figure, the yellow line always represents the input signal from sensor.
Fig. 14. Output Signal of Heart Rate OTA1
Fig. 15. Output Signal of Heart Rate OTA2
Fig. 16. Output Signal of Heart Rate Comparator
Figure 17 to 21 respectively shows the output signal of Respiratory rate OTA3, output signal of Respiratory rate OTA4, output signal of Respiratory rate OTA5, output signal of Respiratory rate OTA6, output signal of Respiratory rate comparator.
Fig. 17. Output Signal of Respiratory Rate OTA3
Fig. 18. Output Signal of Respiratory Rate OTA4
Fig. 19. Output Signal of Respiratory Rate OTA5
Fig. 20. Output Signal of Respiratory Rate OTA6
Fig. 21. Output Signal of Respiratory Rate Comparator
Figure 22 also shows the output shows on the LCD screen, the results after processing on Arduino can display on the value of heart rate and respiratory rate, as shown in the figure, the heart rate is 81 beats per minute(bpm) and respiratory rate 9 times per minute(brpm).
Fig. 22. LCD Screen Results Display
In conclusion, after testing, our PPG system were all working accurate for both heart rate and respiratory rate compared to commercial products, the comparison results are shown in Figure 23. Note that the commercial products cannot shown the respiratory rate, the heart rate result of commercial is on top line.
Fig. 23. Comparison of Heart Rate with Commercial Product