<Meander>(@OldSmokie76) Pretty sure you can get combo devices. For my home plants, I don't test anything so I only have and use pH strips. For our business, we also have and use the pH meter to spot check runoff (although I have been advised to get a ppm meter...baby steps...I wouldn't know right now what to do with a ppm meter...I have the idea, but not the "feeling" of it...stupid way to say it, but there you have it...and I suppose maybe I should get the "feel"...Frank Herbert had something to say about that, naturally).
As for what's typical with testing, I'll say right now that there are other more "experienced" people around here who can comment on testing more intelligently than I can (and I did not say old, I did not), but I can give you my data points. We tested NPK for our soil before & after our last harvest cycle and learned yep, our plants used nutrients and the bigger plants typically used more (I can't remember exactly what the ratios were before/after...record-keeping apparently isn't a strong suit). This simple test wasn't all that informative mainly because we weren't planning to recycle the soil from the last harvest (and we didn’t). But it was also unhelpful because we didn't take enough samples and didn't have a plan for our testing. That's right, no plan for how we might use the data, we stuck it to ourselves. So I guess I learned that we came to testing (clears throat), unprepared. We could have tested how much of which nutrient was used by what cultivar, and that might have given us something to think about anyway. Not there's a noticeable lack of "fucking things" to think about.
Now we're starting to build and grow out of living soil because we think we can grow weed that tastes, smells, and is better using live soil / a viable soil food web. (And that's what it's all about for me, you, and most others I suspect...producing the best, most effective cannabis/product we can.) Anyway, we're getting the full-meal-deal before we put our juniors into harvest containers and holes this time around (nutritional, soil health, and microbiological assays). I'm hoping these series of tests, our post-harvest tests, and the repeated testing we'll be doing for the next few cycles at least will help us determine:
(1) whether/how much our soil is deficient and/or depleted in nutrients, minerals, or microbes (factors influenced by our effectiveness as growers, the quality/quantity of our inputs, and environmental factors...here is where geeking out can be a helpful trait because there is potentially a lot of "fucking things" to monitor and track)
(2) whether our attempt at no-till is doing what we expect in the soil (adding back/preserving nutes, minerals, microbes)
(3) whether our attempt at building a living soil is working
(4) whether we get to a point where we have a viable soil food web
And as luck would have it we do know what our definition of success is...but that's our definition...and that's as it should be...some of it is cost and numbers, but that's, well, quantitative, and there are other more qualitative (and exciting...and secret...like how well does...oh yes, it's a fucking secret) things we're looking at as well. This is going to be fun (I'm already having fun, and I haven't taken a sample yet...soil is still cooking). Later this year I’ll be able to give you a more informed opinion about testing. All I can say now is, I’m all in. </Meander>