pert:
The forum screwed up the URL. Here it is fixed:
https://www.youtube.com/watch?v=EfB_MaIB_Tk
However, I think you posted the wrong link because that's just an explanation of how you need to thump the gauge to get a good reading (I guess some part of the system can be a little sticky). So that might be something to consider for this project anyway.
in my old pneumatic controls days, the spec sheet said that pressure gauge was within 2% after rapping.
I bet if I searched the Marsh Gauge site I could find that technical bulletin on how to rap a gauge.
and yes, in the HVAC world it is spelled gauge, not gage.