A gauge like that just at the pump (if you have a pump) can be a help, but a gauge at the far end tells you a whole lot more. How do you hook your gauges up?
I have most of my gauges at the end of the laterals but I also have one at the beginning of each main. Then I close the valve I have for that main and just watch the gauge, if the gauge looses vacuum fast, I walk that main looking at the bubbles entering the main, fast bubbles indicate a leak. After I check all mains I walk the ends of the laterals, there a leak will sometimes be more subtle but you will find them.
I connect all of my vacuum gauges using a DSD saddle on the mains or a T on the laterals, then I use 36-48" of tubing on the saddle to the gauge, a loop helps as Dr Tim said, then I tie it to a tree to hold it up, I don't yet have any covers but I will try some in the future. I find the gauges to be quite cheap in price, but I think it would be a very expensive gauge before the gauge got much more accurate. I use the cheapest I find and I buy a few spares just in case. I have not seen sap get into my gauges.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.