Hygrometer/Thermometer question

[Foghorn]

Could you please post which ones you use and what you would recommend? I want to buy one soon, but would like an accurate one. Please reply? Thank You

 

[jimnjay]

All I can say is good luck. I have 4 of them. Accurite is one available at Walmart at a reasonable price. I bought a Springfield at Walmart and it is off by about 10%, that is not to say that one you would buy would be off by that much. I would get one that takes regular batteries. I have one that is accurate, that I bought on Ebay but it takes watch batteries and they are expensive and it is not designed to withstand the temp for that long. It works for about 4 days and then it will not register at all. If I take it out for several hours it will state to read again.

Here is a information on how to check the calibration of your hygrometer. It is helpful in that you then know how much to adjust for in taking your readings.

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
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 in this amount of water; instead, the salt should have the consistency of wet sand.

Carefully place the salt/water mix in a re-sealable plastic bag, along with the hygrometer. Note: make sure none of the salt/water mix comes in direct contact with the hygrometer, or the hygrometer may be damaged. Completely seal the bag.

Place the sealed bag aside at room temperature for 8-12 hours. Pick a location free of drafts, out of direct sunlight, and away from heating or cooling vents. The temperature should be fairly constant.

After being in the sealed bag for 8-12 hours, check the reading of the hygrometer. It is best to read it while still in the bag, since if your house air is dry the reading may go down quickly once you take the hygrometer out of the bag.
The relative humidity in the sealed bag with the salt/water mix should be 75 percent. My hygrometer read about 72 percent.
If yours is the adjustable type, adjust the screw or setting so that it would have read 75 percent. You will have to do this very quickly, or remember how much you need to adjust the setting (e.g. for mine, it read 72 percent when it should have been 75 percent, so I would need to set it ahead by 3 percentage points). You may want to put the hygrometer back in the bag for another 8 hours to double check your adjustment.
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. Here are some examples to help:
Case 1: after sitting in the bag for calibration, my hygrometer read 72 percent.

It should have read 75 percent, so the difference is 3 percent. I will now add 3 percent to the readings I take on the hygrometer (e.g. in a tank) to get the actual relative humidity.
Case 2: after calibrating in the bag, a hygrometer read 80 percent. It should have read 75 percent, a difference of 5 percent. I would have to subtract 5 percent from readings when using the hygrometer to get an accurate relative humidity.
Remember: always give a hygrometer about 2 hours to stabilize before

 

[Foghorn]

Jaynie, Thanks for that info. Great to have!

 

[Foghorn]

Do most of you NOT use a hygrometer? Do I not need one?

 

[cadman68]

I use the accurite from walmart, cost about 8 bucks works fairly well, i've never checked it but i have chicks about to hatch so i guess it works good enough.