"Calibrated" a digital hygrometer (WalMart Special)

[Junkmanme]

Folks,

I purchased the 6 or 7 dollar Springfield thermometer/hygrometer (without probe) from Walmart a few days ago. At Noon yesterday, I put it in a Ziplock bag along with a coffee cup 1/2 full of damp salt. (after several hours it should read 75% IF it is "right-on".)

At 3 AM this morning, I took it out. It read 72%. So, it's about 3 percentage points LOW.

Is this "about right" for this type of instrument (particularly the Springfield brand)?

What have been your experiences when calibrating a hygrometer?

-Junkmanme-

 

[mstricer]

I'm interested in that to. Mine is also from walmart without probe, I didn't know you could calibrate those.

 

[Junkmanme]

mstricer,

This "calibration" does not involve an "adjustment screw" or something similar..It merely tells you "how far off" the instrument "reads". Then, If you want 75% humidity, you know that is what you have when your instrument reads 72.

Clear as mud?

-Junkmanme-

 

[kathyinmo]

Yup. That's what I did. I have 4 of the same ones you mentioned. Each one was off ..
1%, 3%, 5%, 7%. I just took a permanent marker and wrote on it, under the humidity %..
ie -1, -3, -5.

 

[magikchick]

I have two of them I put in my incubator. They read pretty close to each other. I don't sweat humidity too much as long as I'm in the ballpark with it.

 

[Fluffy-Butt-Farms]

mine were always ok with the humidity, but they would work for a few days in there on temp, and then eventually just read 101.8....to which i knew if i saw 101.8 the temp had spiked over 103. i've given up on these and am ordering a spot check from brinsea...i just lost 32 eggs thanks to the walmart springfield model.

 

[Junkmanme]

Quote:
That's sorta what I think. "In the Ballpark" should be good enough for humidity.

Temperature is more important. I'm planning to put a couple of thermometers in some "icy water" to see where they register. I've put 6 or seven thermometers in the incubator and not 2 read the same!

I could almost be as accurate just "laying my hand" on top of the incubator!

sheesh!
-Junkmanme-

 

[jenjscott]

Quote:
Looks to me like you lost these thanks to your incubator. A good incubator shouldn't spike like that. That being said, I have over adjusted my incubator and spiked it myself to 104, but my walmart worked. The only trouble I have with mine is when I up my humidity if it goes too high the digital readout blanks out at about 90%.

 

[Junkmanme]

Just a short while ago (today), I ordered an Analog Hygrometer on Ebay. Cost was $5.00 with the shipping included. This Analog Hygrometer has an adjustment screw on the back so that it can be set accurately after doing the "calibration test". Also, I believe that it has a glass lens which won't tend to scratch like plastic lenses do.

It is the type of hygrometer commonly used in Cigar Humidors. I'll see how it compares to the digital that I just put through the "calibration test".

-Junkmanme-

 

[dragonchick]

Quote:
How do you callibrate this type of hydrometer? I picked up one at a sale today for a quarter but it doesn't have any directions.