about digital hygrometers
I have several small-medium humidors and noticed that the digital meters were reading all over the place. I finally put them all in a plastic bag with one oasis humidity source and found they varied by up to 15%. Some old Radio Shack ones (no longer sold) seemed the most consistent, with Csonka (usually a GREAT company) consistently reading very low. If you use a Csonka hygrometer, based on my personal experience, be careful you don't get the humidity too high. If my meters are reading 70%, the actual level might be far too high for good storage.
I'll check out Walmart - never thought of looking there. The old RS meters are small and accurate and I sure wish they still sold them. At $10 they were a deal!