All my hygrometers disagree

Gobi · Sep 15, 2020

Take a look at my hygrometers. The AcuRite meter on the left was purchased today, the others are of various ages, but all had new batteries put in today. As you can see they don't agree on the rh. The probe is for the AC Infinity controller in the second shot. It's even farther off than the Acurite meters.

I know I can calibrate the AC Infinity controller. I don't think I can calibrate the others. How do I know which ones are trash?

BobThe420Builder · Sep 15, 2020

A couple% mean diddly

Attikus112 · Sep 15, 2020

I bough a 12 pack of cheap hygrometers off ebay so I could keep one in each of my jars, and as expected they were all over the place. I just used a RH reference to find out how far off they were then marked the hygrometer with that value. The salt test can be used for a RH of 75% and/or a Boveda for 62%.

quirk · Sep 15, 2020

+/- 2-3% is fairly typical, although it's spot on using Boveda's.

cobshopgrow · Sep 15, 2020

Attikus112 said:
I bough a 12 pack of cheap hygrometers off ebay so I could keep one in each of my jars, and as expected they were all over the place. I just used a RH reference to find out how far off they were then marked the hygrometer with that value. The salt test can be used for a RH of 75% and/or a Boveda for 62%.

when you compare the results you got with the 62% boveda and the salt test, do you get a similar error?
i found the error isnt linear, at 62% they behaved much better then at 75%. (using same cheapo meters 5 pack).

Attikus112 · Sep 16, 2020

cobshopgrow said:
when you compare the results you got with the 62% boveda and the salt test, do you get a similar error?
i found the error isnt linear, at 62% they behaved much better then at 75%. (using same cheapo meters 5 pack).

The error in the reading wasn't as simple as an offset but it wasn't drastically different between the 62% and the 75% for most of my hygrometers. I did have some outliers but i expected that. I suppose my application is a little different though as I'm only using them for jar RH vs grow room RH. I really only needed to know the error for the 65% RH point vs the optimal range for a grow room.

ComfortCreator · Sep 16, 2020

You will be surprised how often taking out the batteries and.putting them back in resets and improves performance. Best i can guess it is like rebooting a pc that goes on the fritz

All my hygrometers disagree

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