One thing that might not have been made clear is the supply air pressure. The Longacre site tells you how to use the tester and they say to set the supply(at the compressor) air pressure to 110psi to 125psi with a max of 175. You just have to have enough so that the tester regulator is set at and can maintain 100psi.
Of course, that doesn't apply to the tester in the photo I posted.
