compression losses of the cylinders Z 650 b2

I made the instrument with only one pressure gauge, so I also eliminated the calibration error.

if I wanted to measure the compression I needed a pressure gauge with 20 bar full scale and unfortunately I didn't have it available.

I cannot imagine that it would work with only one. Even if it is possible, the fact that you cannot get the cylinder up to line pressure means there is quite a leak or the air compressor is not up to the task.