Newbie Calibrating Hygrometer question??

Discussion in 'Incubating & Hatching Eggs' started by aceschix, Jan 22, 2010.

  1. aceschix

    aceschix Songster

    Oct 18, 2009
    New Hampshire
    I have two thermo/hygrometers in a big sandwich bag with a coffee cup 1/2 cup of salt 1/2 cup of water. The large one seems to be correct. It is from Radio Shack.
    The humdity goes from 74% to 76%.

    The smaller one that lots of people here seem to like - a small Springfield from Wal-Mart. Is only at 67%. What do I do now with the Springfiled? Can it be manualy calibrated or is it a dud? These have been in the bag for 36+ hours now. Advice anyone? I have eggs going in early next week.
  2. rebelcowboysnb

    rebelcowboysnb Confederate Money Farm

    Use it an just remember its always about 8% low.
  3. lemurchaser

    lemurchaser Songster

    Apr 11, 2008
    Corvallis, OR
    Other people just mentally know that they are off by a certain percent and make adjustments. So if it says 67% when its 75% then you add 8% to whatever it says. I personally would just trust the one that is right, and not worry about the one that isn't.
  4. Intheswamp

    Intheswamp Songster

    Mar 25, 2009
    South Alabama
    Yelp, just remember that it reads 8% too low.....for example, if it reads 50% then it's probably around 58%.

    You may have just written down a 1/2 of water in error and I'm not too sure if it really matters, but the recipe is 1/2 cup salt and 1/4 water. Basically just a wet soggy pile of salt is what your after.

    Best wishes,
  5. alicefelldown

    alicefelldown Looking for a broody

    Aug 18, 2008
    To calibrate a hygrometer you will need:

    * 1/2 cup table salt
    * approximately 1/4 cup water
    * coffee cup
    * hygrometer
    * large re-sealable freezer bag

    1. Place 1/2 cup of salt in the coffee cup, and add the water. Stir for a bit to totally saturate the salt (the salt won't dissolve, it will be more like really wet sand).

    2. Place the salt/water mix in a re-sealable plastic bag, along with the hygrometer, and seal the bag. Note: make sure none of the salt/water mix comes in direct contact with the hygrometer.

    3. Let this bag aside at room temperature for 8-12 hours, in a location where the temperature is fairly constant.

    4. After 8-12 hours, check the reading of the hygrometer. It is best to read it while still in the bag.

    The relative humidity in the sealed bag with the salt/water mix should be 75 percent (mine read about 72 percent).

    5. For adjustable hygrometers, adjust to read 75 percent. You will have to do this very quickly, or remember how much you need to adjust the setting (e.g. mine read 72 percent rather than 75 percent, so I would need to adjust the dial up 3 percentage points).

    If yours is not adjustable (like mine), simply make a note of how "off" your hygrometer reads. If it reads below 75 percent, you will need to add the difference to your actual readings. If your hygrometer read above 75 percent on the calibration, you will need to subtract the difference from your actual reading.​
    Last edited: Jan 22, 2010

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