Acidic soil is really great, I am always trying to get it, I don't think any ph meters work very well, mine always says my soil is way alkaline like from 7 to 7.5, so I think they can give you a ball park idea, but not a very close idea. You need a real expensive annoying soil test, to pin point the numbers correctly. If I use compost, then test it may get a tiny bit less alkaline. Its just a run of mill cheap kind of meter.

Meters to measure soil pH that cost less then $50.00 will not be reliable enough to give an accurate reading, and they do not tell you what needs to be done to correct any problem they may indicate.
North Carolina State University does soil testing for a fairly nominal fee.

Here is a link that might be useful: NCSU CES

Once you get it done once, if it's in an acceptable range (say 6-7.5), you don't have to amend to change it and compost will keep it there. If it's very high or low and you have to make changes, then you might have to worry about sampling once or twice a year to see how you're doing. But have it tested at a lab first to see where you're at.

7 to 7.5 is not 'way alkaline'. 7.0 is neutral, and unless you're trying to grow a very limited list of plants that demand acid soil, it's perfectly fine for the average garden.