Hygrometer scale

[mad1]

I have a hygrometer dial display, scale is 0 to 100. What is a normal reading for a home with 40 % humidity. How does this compare to the measurement of that a humidity meter displays?
THe meter is reading 75 sitting on my desk.

What I have found is that it measures the relative humidity vs the temperature. Is this a more accurate measurement than the huidity meter?

[Theophylact]

What's your question? A hygrometer displays the relative humidity; it is a humidity meter.

Relative humidity is the percentage of water in the air at a given temperature, relative to the saturation value for that temperature. (It's the partial pressure of water vapor versus the saturation vapor pressure of water.)

The vapor pressure of water increases with temperature. At its boiling point (100º Celsius at one atmosphere), the vapor pressure of water is one atmosphere/14.7 pounds per square inch/760 torr/1013 millibars/101,325 Newtons per square meter. At 20º, it's 17.5 torr; only 2.3% of what it is at the boiling point.

Air saturated with water contains 17.3 grams of water per cubic meter at 20º C. If the relative humidity is 40%, it contains 6.9 grams of water per cubic meter.

At 25º, water-saturated air contains 23 grams per cubic meter, and air with a relative humidity of 40% contains 9.2 grams.

All clear?

[mad1]

Can this be used to meaure the humidity level in my home? If so what is the normal range that I would expect to see?
The meter measures 72 with the temperature of 74 deg.

[Theophylact]

Normal range? That depends on climate and season. If you live in New Orleans and it's summer, "normal" is about 100%.

For most people, the comfortable range of indoor humidity is 30-60%.

[mad1]

My readings at home vary from 35 to 50 during the summer, during the winter I use the hole house humidifier to try to maintain this, close to Chicago.
Is there a one for one ratio on the Hydgrometer scale to the scale on the Humidity meter . I want to use the Hydrometer to verify the readings that I am getting on the Humidity meter at home.

[Mntsnow]

If you are talking about computer rooms most Data Centers try and operate between 40 and 60 % humidity

[Siliconjunkie]

Mntsnow, that brings up an interesting thought for me. Since I live in the humidity capitol of the world and all..

At work we have somewhere around 100k sq/ft of raised floor/server room. As you said the litte displays on the air handlers usually indicate about 40% RH @ 68-70F. The other 60% is going somewhere, and around here that would be alot of water.

I would think that once the air is "dried" and it was recirculating it, the amound of condensate would be low(er). But where does it all go? Down the drain? I will have to corner one of the facilities guys and ask them sometime.

[Theophylact]

I'm assuming that your hygrometer is reading % relative humidity, and that there is a one-to-one correspondence with the "humidity meter".

[mad1]

I will set it next to the humidity meter tonight and read it in the morning.

[no1_vern]

Originally posted by Siliconjunkie
Mntsnow, that brings up an interesting thought for me. Since I live in the humidity capitol of the world and all..

At work we have somewhere around 100k sq/ft of raised floor/server room. As you said the litte displays on the air handlers usually indicate about 40% RH @ 68-70F. The other 60% is going somewhere, and around here that would be alot of water.

I would think that once the air is "dried" and it was recirculating it, the amound of condensate would be low(er). But where does it all go? Down the drain? I will have to corner one of the facilities guys and ask them sometime.

Depending on the type of air handler you may be correct. If it s a chiller/dehumidifier, then yes you may have a drain for the excess water removed from the air to drain to.
BUT most computer rooms NEED humidity, most of them are kept at about 50%. If your relative humidity is always above(or almost always above) 50% or so you will have a chiller/dehumidifier.

In drier climates the air handlers will include a humidifier to increase the amount of relative humidity.