A simple, low cost way to measure the pressure of your dust collector system, I probably have $2 investment in it and it is used almost every time I turn on the dust collector. It will indicate a forgotten gate left open or a plugged line somewhere.
Simply a tube with some water in it (I used some food coloring for a visual aid).
The photos show 1) system turned off 2) one gate open 3) all gates closed.
Technically it is called a manometer and has something to do with the sea level........... whatever. I've been using it for about 20 years and have forgotten the original source, certainly not me.