Use the -r flag and set something like -r 3 or -r 4. This way you get more accurate measurements. Also the -f flag should be set to something between 10 and 60, depending on your needs (like gaming, watching movies, browsing, moving the mouse, click the buttons on the mouse...)
Using phoenix, no command -r.
Also how to make a critical temperature in phoenix when it should stop mining (not GUI phoenix, console).
Is it ok to run fan 100%?