pH Meter, Digital 3-in-1 TDS, pH & Temperature Water Tester pH Pen, 0.01 High Accuracy Reader TDS Meter & PH Tester, pH Meter for Drinking Water, Aquarium,Pool, Hydroponics, Hot Tub, Garden, Wine, Lab

I have a more expensive one now but used to use cheap ones from amazon and they worked fine for as long as I remembered to not submerge them in water. The cheap one by no means lab grade but you just need to know if it's 4,5, or higher. More options but same issue of breaking after a season if I didnt treat it right. Litmus paper the cheapest but you have to store it correctly. To actually use them you take bottled water (unless you have low ppm tap water) and slowly saturate your soil sample (lets say about a pound of soil, half from 3 inches deep and half from 6 inches). What you need to acheive is the full sample to be wet without there being standing water in the cup, so you can add a little water at a time, maybe even walking away and coming back later between applications if your soil is slow to absorb the water. The moment the sample can hold no more water (ie water starts pooling at the bottom), pour out the excess at the bottom. Then let the soil sit for 5 minutes. Finally, get another container, grab a handfull of your soil and squeeze the water out of it like a wet sponge into the new container. This liquid is what you measure. That procedure might aound complicated but really all your doing is getting the soil as wet as it would be after a watering then squeezing that liquid out to be tested. Doing this gives you a low-end estimate of the acidity as when soil is less-than-saturated the acidity will be concentrated. However, this is a good ballpark estimate and doesnt require a laboratory. For blueberries, I like to shoot for pH 4.7.