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Web HumiCalc®

Web HumiCalc Directions

Directions for Using Web HumiCalc

1. When you download HumiCalc, it opens in a new window. Once you close the program, you will need to download the Web version again to run future calculations.
2. The main calculation window automatically appears. It consists of four frames

• Configuration Frame
• Known Values Frame
• Calculated Values Frame
• Units Frame

At times, a Message Frame or a Caution Frame may replace the Configuration Frame.

Humidity conversions in HumiCalc usually consist of four steps:

1. Select Mode. In almost all cases, NORMAL will suffice; it requires the least user input and is less application specific.
   ( More about Modes)
2. Select Configuration.

• Temperature Scale
• Equilibrium over Ice or Water
• Carrier Gas
• Calculation Mode
• A Known Value ( More about Known Values)
• Whether or not to use the Enhancement Factor

3. Select Units. HumiCalc works in various pressure, temperature, and density units. All current system units are displayed in the Units Frame. ( More about Units)
4. Calculate. Web HumiCalc checks for both valid input and valid results and provides feedback in the case of possible errors. ( More about Calculated Values)

Sample: Convert Frost Point to Dew Point

Determine the Dew Point temperature of the air when the Frost Point temperature is -10.00 °F at a pressure of 14.7 psia.

1. Select NORMAL mode

2. Select Configuration

   From the CONFIG/UNITS menu, select DEFAULTS.

   From the KNOW drop-down list in the Configuration frame, select FROST POINT. Note that the %RH in the KNOWN VALUE frame is replaced by FROST POINT.

3. Select Units

   Click and hold the mouse over the CURRENT TEMPERATURE units. A drop-down list of other available units appears. From this list, select F for Fahrenheit. Note that all temperatures on screen, including the known Frost Point parameter, immediately switch to Fahrenheit. Change pressure units to psia in the same manner as you changed temperature units.

4. Calculation

   You're now ready to calculate the resulting Dew Point at a Frost Point of -10 °F and pressure of 14.7 psia. This pressure is referred to as the test pressure. HumiCalc not only calculates the Dew Point, but calculates all other humidity parameters as well. Therefore, it needs to know at what temperature (typically ambient) to perform these other calculations. This temperature is referred to as the test temperature. For this example, assume a test temperature of 70 °F.

   • in the KNOWN VALUES frame, change the Frost Point value to -10.00.
   • using the mouse, the tab key, or the arrow keys, select the TEST TEMPERATURE value and change it to 70.
   • similarly, select the TEST PRESSURE values and change it to 14.7.
   • finally, press the ENTER key or click the CALCULATE button.

In the CALCULATED VALUES frame, the Dew Point is calculated as -14.593°F.

A small check mark appears to the left of the CALCULATE button. The check mark indicates a high probability that this calculation is okay. If the results of this calculation were questionable, a question mark would appear instead. See More About Calculated Values.

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