Attach a mech guage that you know is accurrate---it show show pressure while turning with a drill==
One of the common things we see in customer cars that we install engines in is an inoperative guage
I'm thinking of making a pressure chamber that we can test
oil pressure guages with so we can verify correct operation before we even put an engine in the car, also a system for the temp guages, but that would take several sensors
Jerry