The first 3" analogue gauge for the C172 Sim and Karl is very happy with the design. In his words, "it's simple and it works and it looks the business when its operating".
 
It utilizes a microswitch to home the zero position. Calibration is done in Mobiflight and the unit can be backlit. 
 
Created in several simple sections. The decal plate can be 3d printed or printed using a standard inkjet printer. A separate decal sheet is included. 
 
The adjustment knob is for show only and does not currently operate the temperature scale. 
 
The Build Guide can be found here:
 
https://www.737diysim.com/build-guides-1