Hook a garden hose thread pressure gauge to one of those drain valves, and read the pressure.
Your system is not the usual system. You have a check valve in a place that I would not expect. You appear to have a UV light sanitizer, but those should always be preceded by a 5 micron filter so that bacteria don't have particles that shield bacteria from the light. So that thing with the flex power cable may not be a UV system. I don't recognize the black piping. Is that system really in New Hampshire? But parts of it certainly do look like USA.
I suspect you have some kind of proportional drive system, and the thing with the uncovered wires is a pressure sensor/transducer.
Is the flow from the black pipe up, thru the check valve, to the pressure tank? At first I was suspecting the other way.