I was at Walmart today and they had about 3 different analog models. I was about to buy one but then I noticed every single one had a different reading on it. Since they were all within a foot or two of each other I'm guessing that they are all not very accurate or they would have the same reading. So I didn't buy one. I was afraid the electronic ones would not last long in there (dust and all that) so what's a good one to buy?