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I was looking for advice on which hygrometer would give me the best read-out. I'm trying to maintain even humidity levels, especially now that the weather has changed, and my forced-air heater is now pumping out some serious BTU's.

Also, is there a difference between a HYGROMETER and a HYDROMETER???

Any help would be greatly appreciated!

A hydrometer is used for making wine. I think it measures specific gravity of a liquid. A hygrometer is used to measure relative humidity. It's a common mistake to mix up the two. It looks like Amazon made the same mistake. Most cheap hygrometers won't give you an accurate absolute reading, but they will show you the difference between your highs and lows. That's what's most important.
Tim

Get the kind of hygrometer that the HVAC people use. If you didn't pay ~$90-$130 or more it doesn't work. Unless, that is, if you don't need a device that reads below ~25% RH, then you can get one in the $35-$70 range. If you don't get one that's accurate, just don't bother, because they are so wildly and erratically erroneous that you never know what your reading actually means. It could even be right, but that's a pretty rare occurrence.

https://www.google.com/search?q=sling+hygrometer&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

A sling hygrometer will give you the fastest and most accurate RH readings.

Yes, they are called a "sling psychrometer". I have one of those, too, but the putz factor definitely decreases its convenience. I think by the time that you wet the "sock", swing it for 30 seconds, read both thermometers and then look up the readings in a table that you've spent as much or more time than my HVAC hygrometer.

One thing to be aware of with even expensive hygrometers is that as they age, they "drift". (Mine is in the 15-20 year range and probably should be replaced) The sling psychrometer doesn't do that.

The only thing that needs maintenance with the sling psychrometer are the bulb socks needing to be changed out every couple years. I've used this one for years and its really accurate... http://www.theweatherstore.com/poslps.html

Now you can get a decent digital one in the $50 range and just self calibrate it at the high end ~75% RH using a common salt saturated distilled water at room temperature. To calibrate at the lower end ~33% RH you simply use Magnesium Chloride instead. Once you know how much the digital deviates at these limits you can adjust for their error. They do repeat reliably if you keep their silicon measuring plates clean. Store them in a ziplock bag when not used and they last a good while. In dusty smoke filled areas, the digital ones can get unreliable after a while. The $10-$20 chinese import ones, stay away from, they are less than useless.

Here is a link for the calibrating methods used to test them....http://www.kingofthehouse.com/hygrometer/

Thanks. I knew I had something wrong but couldn't put my finger on it.

In order to really know what's going on in our area, we need readings as low as possible. I regularly get readings in the 10% range.

Excellent discussion on calibrating.

For the time invested in calibrating, I can do something that will let me pay for one already accurate.

Why would a home and piano owner want to read below 25%, or even 10%, and highly accurately?

That's a total danger zone anyway, and drastic action needs to be taken, whether the hygrometer can display it down to a gazillionth percent or not.

Also, I disagree with the notion that a hygrometer doesn't work if it costs less than a hundred bucks. Mine cost $20, and I checked it when it was new (saturated salts). It's a few percent high, especially in the sub-40% range, but it's been working fine, without much drift, for some years now. I have a blue-pink humidity indicator strip with 10% steps, that I checked against the salts. Although not highly precise, it's remarkably accurate.

And the cheap digital hygrometer has been consistently a few % above the strip for 3 years now.

I submit that as a piano owner, the most important thing to know (and control) is the swings in humidity, and to keep the minimum value above about 40%. I aim for 40 - 60% whenever I can. And I think that this is good enough. Whether it's actually 43 - 63 or 38 - 58, I find quite immaterial.

General DTH-700

About $35, accurate to + or - 5% which is excellent. And in NYC I will often see indoor RH levels go from 18% in winter to 70% in summer, so it is extremely important that the range of the hygrometer is wide.

I have had at least 6 clients buy this hygrometer and it always matches the RH of mine within 30 minutes. Usually the client hygrometers that are being replaced are off by at least 10% from the DTH-700.

I think ANY humidity meter is better than nothing and it would be foolish not to monitor your room.

I have the Walmart Acurite at $8.94 US
http://www.walmart.com/ip/AcuRite-Digital-Humidity-and-Temperature-Monitor/16888914
but of course I checked it against a sling psychrometer at work. When new it was pretty close. I imagine it drifts a bit but a regular calibration should tell you how far. Our controls tech says these tend to read low as the sensor collects dust and you should occasionally clean them.

If I owned a more expensive piano, I'd have an Omron Datalogger:
http://www.ia.omron.com/product/family/3028/index_fea.html

No, I have had several customers with under-$100 hygrometers which sat there and totally lied to the customer. I'm talking about showing 40% when in fact it was 20%.

There WILL be the occasional cheap hygrometer that actually works. However, unless a person is knowledgeable about calibration and willing to go through several cheapies if the first ones aren't accurate, then buying one that has some hope of giving a reliable readout is the way to go.

This was posted in the technicians forum and that was originally the context I had in mind. A technician should have a reliable device -- whether by getting a trustworthy unit or taking the time to verify the accuracy of a cheaper one.
As has been mentioned, a sling psychrometer is a device that can be had for a more moderate price and provides reliability and accuracy for a slight ease-of-use penalty.

You've convinced me, I retract my comment.

The cheap ones are getting better and better though.

I think you are right about that. A few years ago one could look over the inventory at "X"-Mart type places and not find a single hygrometer that agreed with another one -- much less with reality. Now, there are apparently many that actually are usable.

The Sauter Masterclass 122 piano has a hygromter built right into the case. What a great idea!

http://www.sauter-pianos.de/english/pianos/m-line/m-line-122.html

Unless your going to sit and record the readings on a regular time frame, you really don't know what the levels are... you need a Data Logger You can get it with a NIST certificate. It will record a reading at set intervals and at every 5 minutes, it will record for approx 60 days. Logging levels range from a reading every 12 seconds to one reading every 12 hours. Includes software, USB connection, creates a graph for you....

If I owned an expensive instrument, I'd use a data logger.

If I had any kind of humidity control equipment installed on any quality instrument, I'd use a data logger.

If I were a tech and installed humidity control equipment on any piano, I'd probably put data loggers in the expensive ones to protect myself from liability. As an engineer I've managed maintenance for the equivalent of a college campus, and I've seen humidity control equipment go bad and do some horrendous damage. At least with a data logger if the piano self destructed you'd be able to prove your equipment installation didn't cause it.

Many of the cheap hygrometers have a min-max feature that one can read out and cancel.

What's a NIST certificate?

National Institute of Standards and Technology... NIST this is the same institute that provides us the frequency standard