What is the maximum amount of turns to calibrate? 15 turns maximum.

What is the accuracy? Supco has no specified accuracy for the VG60. Although Supco does calibrate all VG60's to within 10 % of an NIST (National Institute Of Standards & Technology) certified VG60 @ 100 microns.

When the VG60 is turned on, it reads 5,000 microns and then drops down and to 50 microns and stays there?
The Micron pressure readings have been calibrated at the factory. It is permanent and never needs resetting. However, due to seasonal temperature variations you may have to make a slight ambient adjustment. The gauge is perfectly calibrated when after you push the slide switch to ON , both the Atmosphere and Slide switch lamps are energized. Should the 5,000 micron lamp go on instead of the Atmosphere lamp, insert a small screw driver (included) into the opening at the side of the case, locate the screw and make the adjustment until only the Atmosphere and slide switch lamps go on. Do not overturn the screw, it may turn off the Atmosphere lamp. This information is available in the VG60 instructions under Calibrations.

Can the gauge be hooked up in line? Yes it can but the accuracy will drop and it will have to be cleaned more often.

The display shows "Invalid Calib"? The gauge was never calibrated or somehow became corrupt. Send the gauge back for calibration.

When I hook up the VG64 to a new vacuum pump and isolate the pump, I get an initial reading of 440 microns and then a quick rise to 1200 microns? Always use vacuum hoses not charging hoses as they permeate and leak. Also new hoses have gas in them, so they must be gassed out. If this procedure is not followed, the gases in the hoses will cause a rise in vacuum readings once the vacuum pump is shut off.

When I compare the VG64 to my manifold gauges, the VG64 shows changes but the manifold does not show any changes? The VG64 is more sensitive than the manifold, which will not show defined changes in system.