1. What is Relative Humidity?

Relative Humidity (RH) is a measure of the amount of water vapor in the air compared to the maximum amount the air can hold at that temperature. It's expressed as a percentage and is calculated using vapor pressures at wet and dry bulb temperatures.

2. How Does the Calculator Work?

The calculator uses the Relative Humidity equation:

Where:

• \( RH \) — Relative Humidity (%)
• \( e_w \) — Vapor pressure at wet bulb temperature (Pa)
• \( e_d \) — Vapor pressure at dry bulb temperature (Pa)

Explanation: The equation calculates the ratio of actual water vapor pressure to saturation vapor pressure, multiplied by 100 to get a percentage.

3. Importance of RH Calculation

Details: Relative humidity is crucial for weather forecasting, HVAC system design, industrial processes, and maintaining comfortable and healthy indoor environments.

4. Using the Calculator

Tips: Enter vapor pressures in Pascals (Pa) for both wet and dry bulb measurements. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between RH and absolute humidity?
A: RH is a percentage of moisture relative to capacity, while absolute humidity is the actual mass of water vapor per volume of air.

Q2: What are typical RH ranges for comfort?
A: 30-50% RH is generally comfortable for humans. Below 30% may feel dry, above 60% may feel muggy.

Q3: How do I measure e_w and e_d?
A: Use a psychrometer (wet-dry bulb thermometer) and convert temperatures to vapor pressures using standard tables or equations.

Q4: Why does RH change with temperature?
A: Warmer air can hold more moisture, so RH decreases as temperature rises (if moisture content stays constant).

Q5: What instruments measure RH directly?
A: Hygrometers and modern electronic sensors can measure RH directly without needing separate wet/dry measurements.