Wine Analyzers (Vinmetrica, sentia, etc.)

[winemaker81]

@winemaker81 does not use SO2 testing and simply makes a 50ppm addition each time he opens a barrel.

That's not quite correct. I top barrels roughly monthly, planning for a 1/4 tsp per 19 liters every 3 months. Using a tip posted previously, I add a bit more than 1/3 of the quarterly amount each month. my barrels are roughly 55 liters, so I'm adding a slightly rounded 1/4 tsp at each topup.

 

[Rice_Guy]

rather use slightly more SO2 than necessary, as opposed to being low.
Now, YAN/pH/TA/MLF testing certainly seems to be worth it. For me, those results determine the timing, and type, of interventions I'll do with my wine.

You do have another variable with free SO2 , if you mainly run tannic red wine or traditional tannic apples they act as natural antioxidants. Traditional tannic wines can work.
I started running YAN with Vinmetrica reagent kit and a pH meter. At this point I would say happy yeast make good wine. Not knowing nitrogen is tossing darts. (formal titration is run outside or by a bathroom fan, but I was probably exposed to more in HS dissecting)
I have malic test strips which can say you are at the end point. pH is essential, it act as a preservation system, avoid TA till time to bottle.