Differential and Single ended Measurement

Goal

In this lab we will understand how to compare the quality of the analog signal measurements from a sensor using a single-ended and differential pair measurement and explore signals on the I2C bus.

Background

We used TMP36 temperature sensor as a voltage source for the ADS1115. By placing it at the opposite end of a solderless breadboard as where the ADS1115 module will go, we were able to add some noise to the ground return path and see the difference between a differential and a common signal measurement. We measure the voltage on the temperature sensor using a single-ended measurement and simultaneously, a differential measurement. We found that the single-ended measurement will be more sensitive to noise (IR drop) on the ground line while the differential measurement will not be sensitive to this noise.

Circuit Setup

Differential and Single ended Measurement plot

When we create a current noise by pushing a constant current of 0.5A to the ground line with the help of power supply, I measured the voltage across the two ends of the ground line. The below figure shows that red line is a differential measurement and yellow line is single ended measurement which has positive and negative noise coupled.