Cheap and fairly accurate digital humidity meters

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FlyingPenguin
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Cheap and fairly accurate digital humidity meters

Post by FlyingPenguin »

I needed a couple of of good humidity meters for my cigar humidors. The mechanical ones are crap. Based on reviews I ordered four of these for $16 (they come in a four pack), figuring I could find some other uses for them.

https://www.amazon.com/gp/product/B07GNMKYCZ

It's encouraging that all four read exactly the same humidity (once they settle down - they do take a while to settle down to a humidity change) and are withing a half a degree of temperature of each other. They also matched up pretty close to a more expensive (and a lot larger) humidity meter I own.

They're small and unobtrusive. They run on 3 small watch batteries. My only grumble is that all four were already powered up on arrival and there's no telling how long they've been sitting on a shelf using up the batteries or how long they'll last.

I ended up using the extra two in my watch cases in which I keep a small bag of desiccant to keep the humidity low.

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Executioner
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Re: Cheap and fairly accurate digital humidity meters

Post by Executioner »

I've calibrated several of these when I was doing tech work. The typical accuracy for humidity is +/- 5%, but when you start going below 10%, it' gets difficult to measure humidity with these type of sensors, and the accuracy gets quite large. We have a really good one that we bought from Vaisala that costs >$1000. We also purchased a $25,000 standard chamber from Thunder Scientific that has an accuracy for humidity of +/-0.5%. We use that chamber to calibrate these type of sensors.
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FlyingPenguin
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Re: Cheap and fairly accurate digital humidity meters

Post by FlyingPenguin »

Yeah I don't need them to be crazy accurate, just better than one of the mechanical dial ones that comes with the humidors - those things are worthless. I just want to know if the humidor is somewhere between 65 and 75%. Cigars get brittle below 65.

I don't really need them in my watch box but it's nice to know that it's staying a little dryer in there than the rest of the house, and since I had extras WTH. For the money they do the job.
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Re: Cheap and fairly accurate digital humidity meters

Post by Executioner »

If I was still located in our Southern CA site, you could have sent me just one of them, and I would have checked it at 5 points between 20 and 90%RH. I would have then created a linear regression table taking into account the error in the sensor with the compensation of the linear regression. With the table, you would then know when it read a value, the table would show you the correct RH.
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