Measurements
Before verifying the full functionality of our system, we first need to test whether the components connect well with each other on the PCB. Then we should verify if the LDO provides the correct 1V DC supply for our chip. And also the output voltage of these two voltage dividers should be 0.5V and 0.6V.
For the chip testing, we adjust the potentiometers to generate the bias current (20uA) and then connect the current to our chip. After all these tests were done, we begin to verify the functionality of our system by using a voltage generator to generate 5V to feed into the LDO. Then we use Arduino to power the chip and process the output signal at the same time, and finally display the results on the LCD.
Fig.1. to Fig.5. show the measured signals of our system. Fig.1. is a real PPG signal acquired from the optical sensor. Fig.2. is the first OTA’s output. Fig.3. is the second OTA’s output. Fig.4. is the voltage signal measured at the comparator output. The comparator output will be fed into Arduino for further analysis. Fig.5. shows these four outputs in one plot for comparison.
