A whole new setup
I did mention that I am currently running an apprenticeship with Adrie Pijnen, shipwright. He is a frontrunner in the application of vacuum infusion, so there is a lot one can learn from him. He is also a nice man, happy to show what he has found out. He builds his own (but also many for others) vacuum installations.
I showed him my concoction. He laughed his head off. Such a little pump! A gastank! A vacuum advance unit for a pressureswitch!
I'll make you a tank, he proposed. Complete with all the connections to build a serious, however tiny, installation.
He welded a tank, 45*25*20 cm (17.7"*9.8"*7.8"). My little Robinair tightly fit on the top. Two valves, the pressure gauge, a connector for the pressure switch and one more connector in reserve. (Adrie, many thanks for this beautiful installation!)
He also gave me two ready to use pressureswitches. For him they were not applicable: Too little switching power, but more important, almost no hysteresis. The points at which the pump was switched on and off almost coincided. (In that case the pump switches on and off so rapidly that it will soon break.)
I took the two switches and put them together with a relay. The result looks funny, but in fact works very precise. The left switch controls the pressure at which the pump is turned off, the right indicates the point on which it is turned on again.
I am able to get the points as close as 0.04 bar together! (But also as far apart as I might wish)
I suppose I am ready now to experiment with my first injection.