| In order to begin learning how to calibrate a | | | | that the digital type hygrometers will most likely |
| hygrometer, you will need a small container which | | | | lack a way of resetting or calibrating the readings |
| will hold one teaspoon of iodized salt. A completely | | | | that they take, so will need to adapt to this using |
| flushed out laundry detergent bottle cap might be | | | | other means. |
| just the thing, or you could find something smaller | | | | Once the bag or container has been sealed in an |
| still. To the level teaspoon of salt, and on a flat | | | | airtight manner with both the slat solution and the |
| surface, add just enough water to produce a wet | | | | hygrometer, you will let it sit unopened for no less |
| paste. You will want to be careful not to flood or | | | | than 6 hours, with 7 hours being ideal. At this |
| over moisten the salt. If your hygrometer is | | | | point, you will open the container and check the |
| digital, be sure to turn it on before proceeding. | | | | reading on the device. If your hygrometer is |
| Analog and digital models should be clean and at | | | | calibrated correctly, it should read within 2 |
| the ready. | | | | degrees either way of 75%. If it does not read |
| Your next step is to find an airtight storage | | | | within this allotted range, your analog hygrometer |
| container or sealable plastic storage bag that will | | | | will need to be adjusted with the use of a flat |
| easily fit both the cap of salt solution and the | | | | head screwdriver. For a digital misread, you will |
| hygrometer that you mean to calibrate. Because | | | | need to calculate how many degrees it is reading |
| this salt and water solution will always produce a | | | | off by and add or subtract them each time your |
| humidity reading of 75%, this a fail proof way of | | | | test your device. |
| testing and setting your hygrometer. Remember | | | | |