The first video is of the tach capability side by side with an off the shelf tach. It shows the tach in line with the off the shelf one as a calibration test.
The second video shows the calibration of the sensor board and User Interface in calibration with the vacuum hand pump and the vacuum gauge. The sensor board is not connected to the truck vacuum system.
The third video shows the sensor board and mechanical vacuum gauge connected to the truck vacuum system. The hand pump is no longer connected.