Inconsistent hygrometer readings

[Peter11216]

Hello All,

I'm curious to know if anyone either knows what is going on with my hygrometers or has a good theory.

Here's what is happening:

1. I put each hygrometer in a sealed plastic bag with wetted salt for 24hrs. Hygrometer A read 71%; hygrometer B read 72%. Both are off, but A is reading less than B.

2. I put both my hygrometers into the same humidor, one inch apart, and one day later A reads 62%, and B 61%.

Hygrometer A should always be 1 percentage point lower than B if the reading changes linearly with changes in relative humidity.

What's going on?

Best,

Pete

[tmac77]

Welcome to the world of $12.95 hydrometers. I would not worry too much about a 1% variance. If it were a higher (over 3%) then you may; 1. have an issue with the hydrometers 2. have an issue with your humidity levels.

Sorry not to have been able to wax more eloquently upon various theories regarding relatatvie humidity but thats all I've got.

[Peter11216]

It's funny that I did actually pay $12.95 for one of them.

Welcome to the world of $12.95 hydrometers. I would not worry too much about a 1% variance. If it were a higher (over 3%) then you may; 1. have an issue with the hydrometers 2. have an issue with your humidity levels.

Sorry not to have been able to wax more eloquently upon various theories regarding relatatvie humidity but thats all I've got.

[PigFish]

Pete if you actually looked at the specifications for most RH sensors you would find that they are not linear charts. Most of them will (at least the ones I have seen) have published accuracy for a given range. These inexpensive hygrometers are not only not certified for accuracy within a given range, they are not certified to give a linear response. Even the certified instruments will not have published linear accuracy from 0 to 100 RH. While it is intuitive to think that you can establish a linear relationship between two of these things I am sorry to report that you are expecting too much from them!

So what is a couple of RH amongst friends? -Piggy

[Peter11216]

Thanks much. I shouldn't have assumed the hygrometers always stayed x% away from the "true" reading. Having read advice about using the salt test, I was under this impression.

Pete if you actually looked at the specifications for most RH sensors you would find that they are not linear charts. Most of them will (at least the ones I have seen) have published accuracy for a given range. These inexpensive hygrometers are not only not certified for accuracy within a given range, they are not certified to give a linear response. Even the certified instruments will not have published linear accuracy from 0 to 100 RH. While it is intuitive to think that you can establish a linear relationship between two of these things I am sorry to report that you are expecting too much from them!

So what is a couple of RH amongst friends? -Piggy