This wiki is a community-maintained resource about everything there is to know about IPFire.
The page Hardware-Diagrams lists information about the CPU-temperature, performance of the fans and since version 2.3, the ACPI
The first diagram visualizes the hard drive temperature.
For every further hard drive installed, a separate diagram is created with the exception of external USB hard drives, as reading the temperature sensors is currently not possible.
On some IPFire systems you might see the following thermal zone diagram. Normally, several temperatures/fans should be shown here.
The next diagram displays the CPU and case/board temperature. Depending on the configuration of your IPFire system, you will see more temperatures than in this example.
Similar to CPU and board temperature, the fan view can contain more diagrams, depending on your system.
The voltages supplied by the power supply is displayed in the next diagram. As you can see, the power supply shown here is not the best one but it is ok for this purpose.