water line pressure regulator & pressure gauge.

[Tex]

I wonder if this would work in a single-boiler espresso machine?

I was thinking of John's bamboo Carezza when I saw this listing; maybe putting it between the pump and boiler, so one could monitor and adjust the group pressure on the fly.

Hmmm?

[Tex]

I didn't mention this before, but one thing that struck me is that it'd be possible to adjust the pressure during the pull: Maybe start out at 7 bar and slowly bring it up, or vice-versus?

[John F]

It would work (sort of) but you need a massive coil to eliminate needle flutter.....trust me.  

I started out like that but eventually had to do a legit OPV and a liquid filled gauge.


Part 2
My guess is that the measure is too gross to profile during shots as you would be making CRAZY swings, but that is just a guess,
 

[grinderz]

I didn't mention this before, but one thing that struck me is that it'd be possible to adjust the pressure during the pull: Maybe start out at 7 bar and slowly bring it up, or vice-versus?

Or even simply step the pressure during the pull ~7 bar for the 1st 3-4 seconds as a sort of pseudo-pre-infusion stage before full pressure comes on for the rest of the shot.