I picked a digital thermometer\u00a0from eBay.\u00a0This unit also displays the relative humidity — the amount of moisture in the air. The temperature reading was pretty accurate (I matched it against the other thermometers I have). As for relative humidity (the digital hyrgrometer), I didn’t have another device to compare it to.<\/p>\n
I looked online and found that you can test the accuracy of the hygrometer by using a solution of salt and water. The materials used are: salt, water, a small container, a sealable plastic bag and a timer (or clock).<\/p>\n
The procedure is really straight forward. You need a small amount of salt. Then add even a smaller amount of water. The water should only wet the salt; the target consistency is similar to\u00a0wet sand. If you add too much water, you can use a tissue to soak it up. It’s then a matter of waiting.<\/p>\n
From the research I did, the wait time seems to be around 6-8 hours. A properly calibrated hygrometer will read 75%. For my test, I marked the reading at 6 hours, 7 hours and finally 8 hours. I based the accuracy of the hygrometer from the average of those readings. Is my reading going to be accurate? Probably not too accurate, but it’ll be close… it’s a lot better than taking the digital reading at face value.<\/p>\n