I typically seem to go against the grain, I'd go with a hygrometer designed for humidors. The analogue ones are around 10$ and can be calibrated. Out of the box I have now tested 7 and all 7 are perfectly accurate (standard salt test) The digital ones (acu-rite,3 zoo meds, and a zilla) were terrible the zoo med reads 27%,34%,29% low. The acurite was a touch better at 18% low, the zilla was 13% high. Then there were 7 analogue bi metal ones that were all the same and all accurate. I'd go with one of them just check at a high end cigar shop.