Pitch gauges
The Robart unit is one of the more accurate pitch gages. Most others rely on you eyeballing the top of the gage to the flybar.
What you are seeing is the inherent slop in the pitch and cyclic control system. If you grap the blades and twist them while the pitch gage is on then you will see at least a degree or two of movement. The easy way to get consistant readings is to move the pitch stick the same way every time before adjusting the numbers. So start out at 0 deg, install the gage, wiggle the blade back and forth to find the natural center. Then do the positive part of the curve. Go all the way negative then move up to the desired positive stick position and adjust. Then move the stick back down and then back up to the next positive position. Once the positve is done return to zero and do the negative curve the same way (go all positive first then to desired neg position).
With the build in slop in the control system, you will get different pitch readings when you move the stick from neg to pos vice pos to neg. So always move the stick to the desired position from the same direction to get consistant readings.
Fritz