Missing voltage or fan data

Vitals reads sensor data from the /sys directory. If sensor data exists, it will show it. A handful of motherboards do not provide metrics for voltage and/or fan. In this case, Vitals will not display data. Personally I have a Dell XPS 13 and cannot track voltage data.

Some laptop fans run at 0 RPM until your CPU heats up, in which case you can also turn off the option "Hide Zero Values", then log out and back in to Gnome Shell.

Most distributions have a command called sensors which will output the same information as Vitals. If you think you are missing a sensor, you can run sensors-detect to see if additional hardware is detected. If it is, log out of Gnome and back in for Vitals to see the changes.