I have a vacuum gauge that I would like to read and report the values from. The gauge expects a 9-30VDC input power, and has pinouts for
Analog- with a 0-10V range.
I'm currently using an ESP32C3 Dev board, and an ADS1115 to read the analog voltage with the following circuit (ESP32C3 omitted for clarity):
GND of the ADS1115 are connected to the ESP32C3 directly, and I'm reading the ADC in differential mode.
The Plot Thickens
The weird part is this: When I power the ESP32C3 from my laptop (a Lenovo machine running windows) everything works perfectly fine. I get the expected voltage values, and the conversion works perfectly. When I power the ESP32C3 from my collaborator's laptop, the ADC reads between 0.5 -> 1V less than expected. I measured the voltage between the
GND pins with my laptop (PC) connected and got ~ +4.7V. With the Mac connected, I measured ~+4.9V.
My big questions are these:
- Why is this happening? Is it a difference in internal voltage reference between the two computers?
- What can I do to mitigate this issue?
- Could this be related to current-limiting/power-saving features on the USB ports?