Measuring Humidity Tool

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Measuring Humidity Tool

Postby Tom Gilleland » Dec 15, 2010 5:39 pm

I need to measure humidity in a variety of caves. I've noticed that some cave researchers use Sling Psychrometers, but I've read that they have some accuracy problems with temperatures 80 to 100 degrees F. I've also read that some people prefer the Digital Psychrometers/Hygrometers. The prices on these range hugely from $5 to hundreds of dollars, but it is hard to guess which ones are accurate. I want a sturdy, light-weight unit to carry in the field and take one-time measurements in each cave.

Can anyone make suggestions? Thanks!
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Re: Measuring Humidity Tool

Postby NZcaver » Dec 15, 2010 8:29 pm

Tom,

Are you familiar with Hobo loggers? They have various models including basic temp/humidity. I've used Hobos for cave projects (not temp/humidity), and they work quite well. I modified my own ones for better functionality.
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Re: Measuring Humidity Tool

Postby ArCaver » Dec 15, 2010 8:30 pm

Tom Gilleland wrote:I need to measure humidity in a variety of caves. I've noticed that some cave researchers use Sling Psychrometers, but I've read that they have some accuracy problems with temperatures 80 to 100 degrees F. I've also read that some people prefer the Digital Psychrometers/Hygrometers. The prices on these range hugely from $5 to hundreds of dollars, but it is hard to guess which ones are accurate. I want a sturdy, light-weight unit to carry in the field and take one-time measurements in each cave.

Can anyone make suggestions? Thanks!

I've used sling psychrometers for years, for HVAC work and on wildland fire. I've never heard anything negative about their accuracy in the 80-100 degree F range.
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Re: Measuring Humidity Tool

Postby Tom Gilleland » Dec 16, 2010 1:02 am

NZcaver wrote:Tom,

Are you familiar with Hobo loggers? They have various models including basic temp/humidity. I've used Hobos for cave projects (not temp/humidity), and they work quite well. I modified my own ones for better functionality.

I've used Hobos for long term data collection, but I need to measure scores of caves only once. Many of these caves are difficult to get to, so I will only visit them once.
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Re: Measuring Humidity Tool

Postby Tom Gilleland » Dec 16, 2010 1:06 am

ArCaver wrote:I've used sling psychrometers for years, for HVAC work and on wildland fire. I've never heard anything negative about their accuracy in the 80-100 degree F range.

Do you know what brand or model you used? The prices vary alot.
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Re: Measuring Humidity Tool

Postby NZcaver » Dec 16, 2010 1:54 am

Tom Gilleland wrote:I've used Hobos for long term data collection, but I need to measure scores of caves only once. Many of these caves are difficult to get to, so I will only visit them once.

Sorry, I totally skipped over that last part of your original post. Not sure if a Hobo is precise enough for your needs, but here's the specs of the U12-011 at a cost of $115 plus software (unless you already have it).

Measurement range:
Temperature: -20° to 70°C (-4° to 158°F)
RH: 5% to 95% RH

Accuracy:
Temperature: ± 0.35°C from 0° to 50°C (± 0.63°F from 32° to 122°F)
RH: ±2.5% from 10% to 90% RH (typical), to a maximum of ±3.5%

If this is good enough, you could bring the Hobo into the cave, press the event button, and log the temp/humidity multiple times at rapid intervals. Then download it later and average the results. Just an idea. And no, I'm not a salesman for Hobo. :big grin:
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Re: Measuring Humidity Tool

Postby ArCaver » Dec 16, 2010 5:57 am

Tom Gilleland wrote:
ArCaver wrote:I've used sling psychrometers for years, for HVAC work and on wildland fire. I've never heard anything negative about their accuracy in the 80-100 degree F range.

Do you know what brand or model you used? The prices vary alot.

Bacharach. If you use any of the slings it's recommended you use distilled water on the sock and replace the sock regularly. Dirt and mineral buildup changes the wetbulb reading. If you have the money it might pay to buy one of the Kestral units for the wind speed function. I've got a very old anemometer made for balancing airflow in ducts that I've used underground, but it's a bit fragile.
http://www.forestry-suppliers.com/produ ... sp?mi=5446
http://www.forestry-suppliers.com/produ ... er+Station
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Re: Measuring Humidity Tool

Postby Tom Gilleland » Dec 16, 2010 7:12 pm

This Kestrel 3000 tool looks very good. The reviews are strong, and the price is not too high. Thanks for your suggestion.
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