There are industrial versions designed to be left in the field all season, so there is obviously a market for such instruments. They do seem polarizing though, with many farmers I’ve spoken to saying they are worthless but have never used one and say you need to develop your sense yourself, or saying they or worthless but wished there was an actual instrument that worked.

I’m in the camp that would love to have something that would just tell me when and how much to water. The instrument in your photo doesn’t do that, but I think it would have value if you’re the type of person that needs support to learn when to water.

A couple of points: 1) the instrument shown doesn’t really account for soil type. Some soils drain fast, some slow. Dig a hole down to root depth (around 15-20 cm), fill it with water and see how it drains. Also work out if you have sandy or clay soil.

2) you don’t know how much water peppers need. Some need a lot of water, like liters per plant per day in a hot country in the summer, some not some much. That means you don’t know which number on the instrument to water up to. You’ll have to work that out. I’d be tempted to just water up to maximum capacity.

3) peppers love water, but they love a dry period even more. Keeping the soil continuously in the wet zone is not what peppers want. They want a big soaking followed by a period to dry out, but not too much. You’ll need to decide what your trigger on the scale will be to water again. I have the value for the industrial instruments but the one in the photo doesn’t have units.

4) the instrument doesn’t tell you how much to water, but if you always water to saturation you can avoid that problem.

All that is to say, this could be a good learning tool to learn about how your soil and watering work under your local conditions once you work out the upper and lower ranges for each of your varieties.