After the first test, I wanted to return the unit, so I thought, this can not be such a big difference compared to the display of the compressed air gun. Then I checked and found that the manual testers very large deviations between the device with another manual pressure gauge. However, the digital test instrument always returns the same value. Conclusion: The digital tester makes sense! A praise to the good service of the company Komerci oHG [Geschwister-Scholl-Str. 1, 96106 Ebern, [...]], where I bought the unit through Amazon.
