I dont know about anyone else, but I have found any of the ones I get from the pet store end up being junk and either break easily or stop working not long after purchase...
I now just get cheap digital ones from a hardware store such as Home Depot or Canadian Tire.. I have 3, and they all show the same numbers (+/- 0.1-0.3). So far they have lasted a lot longer than my expensive flimsy pet store ones..