DPT

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DPT Relative Humidity Charts

• Handy Dandy Earth Science Reference Tables Page
  747

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HUMIDITY
The ratio of the airs actual water content
to its potential water vapor content at a given
temperature.
Relative Humidity
Weight of Water Vapor in Air
Relative Humidity
Weight of Potential Water Vapor in Air at
Saturation

• Basically, relative humidity tells you how
  saturated the air is with water.

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HUMIDITY

• A psychrometer is used to measure relative
  humidity.
• The dry bulb measures the air temperature
• The wet bulb gives a measure of how unsaturated
  the air isthe evaporation of water from the wet
  bulb lowers the temperature reading (and the
  evaporation depends on the saturation of the air)

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Dewpoint Temperature The temperature the air
would have to be cooled to saturate the air
(causes water to condense
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The Dry Bulb

• Dont let it fool you. It is just a thermometer.
• It measures the air temperature.
• Duh!

20C
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The Wet Bulb

• Has a little wet booty tied to the bottom.
• Gets cool when water evaporates.

12C
Wet Booty
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A Dry Day

• A lot of moisture will evaporate.
• The wet bulb will be a lot cooler than the dry
  bulb.

20C
Difference between wet bulb dry bulb is 12 C.
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A Humid Day

• A little bit of moisture will evaporate.
• The wet bulb will not be much cooler than the dry
  bulb.

20C
14C
Difference between wet bulb dry bulb is 6 C.
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Page 747 750 of your Handy Dandy Earth Science
Reference Tables

• Warning 1 Be sure to READ the correct chart
  DPT or RH
• Warning 2 Dew Point Temperature IS NOT
  Difference between wet bulb and dry bulb.
• Warning 3 The wet bulb temp IS NOT the DPT.

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Dry-bulb temperature is your air temperature.
20 C
11
14 C
12
4 C
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Subtract (the difference) between the dry bulb
and wet bulb
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20C
14C
20-146
15
18C
16C
18-162
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Put it all together
20C
8C
20-812
Relative Humidity 11
17
14C
10C
14-104
Relative Humidity 60
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The Dew Point Chart works the same way
14C
10C
14-104
Dew Point 6C
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Try These.
Dry Bulb Wet Bulb R Humidity DPT
26C 20 C
6 C 5 C
12 C 8 C
18 C 17 C
14 C 14 C
0 C -3 C
58
17 C
86
4 C
57
4 C
91
16 C
100
14 C
45
-9 C
20
More Difficult.
Dry Bulb Wet Bulb R Humidity DPT
21C 19C
11C 6 C
17 C 17C
2C -3 C
9C 6.5 C
70F 60 F
82
18 C
45.5
-.5 C
100
17 C
20
-17 C
69
3.5 C
15 C
52
11 C(50 F)
21 C
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The End