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Hello all,

I was trying to find ways to humidify my room and doing some research on hygrometers. I found that in general, a lot of them don't seem to be accurate.

Have any of you had experiences with them/know which ones are good and bad?


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(You might be interested to know that a somewhat uncredible professor claims Monday was the most depressing day of the year. So it's all uphill from here.)

Hi Chris

I'm in a similar predicament. I initially bought a Timex digital hygrometer on Amazon ($15). I heard that one needs to calibrate these devices. My piano dealer told me they wrap their sensor in damp paper towels which should result in a 100% humidity reading. Frankly this struck me as a bit off. In any case, that didn't really work for me, nor did another test I read about involving a cup of very salty water placed in a sealable plastic bag along with the hygrometer. Long story short, I also bought a Venta hygrometer. The two hygrometers are typically 5% or so apart, which I've been told is the margin of error, but sometimes it can be wider. The problem is that they can also be pretty inconsistent with the digital hygrometer built into my humidifier. On good days, maybe everything is with several percentage points of one another. But on bad days there can be quite a bit of variability which can be pretty disconcerting, since I'm a new piano owner. Hope someone else on the Forum can offer some suggestions for both of us!

I don't think you will get a perfect hygrometer at consumer level pricing. I think you will have to spend hundreds of dollars to get something that is truly accurate.

That said, I have been using humidifiers and hygrometers for over a decade, and have been through quite a few of both, and the typical $20-30 units are fine, as long as you understand what they are.

I buy mine at Radio Snack. I don't usually "calibrate" them (too lazy). I just pop batteries in and go.

I have five in the house right now. Two are in the living room, where the piano is, and there is also one built in to the humidifier in that room (a larger size Honeywell cool mist machine). The hygrometers are about five feet from each other, near the piano. They tend to read within 3-5 points apart. The one on the humidifier, which is across the room (25 feet away) typically reads up to 5 points higher than either. This makes perfect sense to me -- the rh is no doubt higher near the machine.

It's an imperfect science, but it is probably adequate. If your $20 digital hyrgometer says 35% rh, it's probably somewhere between 30-40, and mostly ok, imo. FWIW, without the humidifier in the living room, it will hover around 20 right now. So the thing is working hard to keep the room from being parched dry.

On an amusing note, I walked into the local Radio Snack the other day and told the clerk, "I need a hygrometer." From the look on her face, I knew instantly she had *no* idea what a hygrometer does. I watched her struggle for a minute (sadist that I am), then told her it measures humidity. Whereupon she said "that's a thermometer." Alas. Education. Ain't it great.

I've found that the digital hygrometers are best used as a high/low gauge, rather than as a precise measuring tool.

The next-door neighbor to our shop is a HVAC, business, and even their very expensive 'professional grade' gadgets can be off. One of the problems (I am told) is that dust always finds its way inside--making the readings inconsistent.

For the shop I use a sling-psychrometer. From there I can adjust the settings for the steam-unit on our furnace if needed. Usually once it's set for the winter, it doesn't need much adjusting, unless we get one of the 60 degrees and raining weeks in January.

I have not seen discussion here about using a wet bulb, but this method is, I believe very accurate. If anyone is interested I could post a picture of such a unit.

I'm interested--please post it, ejsauter.

If you don't need a constant reading, use a sling psychrometer. That's what we use in the scientific world. They're cheap and very accurate.

Don
Kansas City

One of the other things to take into account it that most digital Hygrometers need a two point calibration. A high and low reading to take into account the curve of the sensor.

The type of sensor in the hygrometer will also play a big roll in how well it measures. I have found that a horse hair sensor on a analog (chart recorder) hygrometer works great.

As pointed out by Rich, the condition of the sensor will affect readings. Dust in the sensor will hold moisture and skew readings.

Most hygrometers are used a "dip sticks". Just to give you an idea of where the humidity is "relatively",there is reason it is called relative humidity.

I bought my hygrometers in the local hardware/DIY store. A cheap "analog" model, costing just a few pounds. They had a dozen or two hanging on a rack. I looked through these, and there was quite a scatter among the readings. I reckoned that the true humidity was likely to be in the middle of this scatter, and selected a few to purchase accordingly.

Not very scientific, but I would be surprised if the values were considerably wrong.

When I purchased my humidifier, I found that the hygrostat setting was wildly different (maybe 20%) from the hygrometer readings! I returned the humidifier to the shop, and they found that the hygrostat was indeed wrongly set.

If anyone can recommend a hygrometer with defined accuracy and at a reasonable price, that would really be very interesting.

http://www.ambientweather.com/slps.html

Don
Kansas City

I'll get a picture taken tonight.

I've been taking a look at these:

http://www.giftngadget.com/taylor1330p.html
http://www.ambientweather.com/mo777hy.html
http://www.amazon.com/Western-Humidor-Caliber-Thermometer-Hygrometer/dp/B0007W1EA6

The second one is appealing because it's more transportable. I think I'm leaning toward the third one because it has continuous readings and seems to be relatively accurate.

Still waiting on those wet bulb pics...!

I bought the $19.95 Radio Shack digital hydrometer and it seems to work OK. The humidifier's reading and the Radio Shack seem to be within 5 points of each other most of the time.

You might be entertained by my tech's comment...he said that our wood floor is a hydrometer as well! When we had some very dry conditions, the gaps between the planks were noticeably wider!! Not as bad now, with correct humidification.