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You can learn how to find the dewpoint temperature by using a psychrometric chart. |
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The Psychrometric Chart |
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At first glance, the psychrometric chart at right may look hopelessly complex, but the truth is that it only displays four measurements that interest us.
· Dry bulb temperature · Wet bulb temperature · Relative humidity · Dewpoint temperature
Click on the illustration to see a full size, printable version of the chart. |
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The vertical lines on the graph represent dry bulb temperature in °F. |
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The diagonal lines on the graph represent wet bulb temperature in °F. |
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Dry Bulb Temperature |
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Wet Bulb Temperature |
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The curved lines on the graph represent relative humidity as a percentage. |
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The horizontal lines on the graph represent dewpoint temperature in °F. |
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Relative Humidity |
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Dewpoint Temperature |
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Dry Bulb Wet Bulb Dewpoint Humidity |
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Using the chart is easy. In this example, there is a dry bulb reading of 79 °F and a wet bulb reading of 66 °F. From these two measurements alone we can see from the chart that the relative humidity is at 50% and that the dewpoint temperature is 59 °F. |