I'm a chronic overwaterer. Most of my houseplants are living but not thriving. I'm just wondering if those meters that measure the moisture in the soil, and the pH of the soil, and light are actually beneficial, "legit" tools. If so, what should I look for, as far as...Which brand/model number do you love? Is an all-in-one device as good as a single device for moisture, a single meter for pH, etc. I would really appreciate some help with this!
The inexpensive meters you're probably talking about don't measure moisture, they measure electrical conductivity, and as such are better at determining the soil's fertility level (salt concentration) than its moisture level. To illustrate, dip a clean probe into distilled water & note the DRY reading. Add a sprinkle of fertilizer or table salt & watch it go to WET. The ions in the salt or fertilizer turn the formerly deionized water into a conductor of electricity and the gauge registers it.
Also, there is very little a hobby grower can do to control pH on a day to day basis w/o a significant array of chemicals that contain nutrients and are either acidic or basic. You can create trends through fertilizer choices, or add acids to your irrigation water that ensure your soil won't creep upward in pH due to high pH tap water, but you'll drive yourself crazzy trying to maintain a stable pH. Also, I wouldn't invest in any pH meter you can't calibrate against a solution of known pH.
My suggestion is, get a wood dowel or bamboo skewer & stick it deep in the pot when you think it's approaching time to water. If it comes out damp/cool/dark-colored from the soil, wait to water. For small pots, feel the soil at the drain hole or heft the pot. If the soil feels dry at the drain or is obviously light when you pick it up (you'll get the knack of this quickly), it's time to water.