Description

Hygrometer Wet & Dry Brannan

The Brannan Wet & Dry Hygrometer is a classic instrument designed to measure the relative humidity (RH) in the surrounding air. This simple and reliable tool utilizes the well-established psychrometric principle, making it a popular choice for various applications in homes, workshops, and laboratories.

Components:

• Two Thermometers: The hygrometer features two thermometers mounted on a sturdy frame or housed within a protective case.
  • Wet Bulb: One thermometer, known as the wet bulb, has a wick wrapped around its bulb. This wick is designed to be dipped in clean water before taking a reading.
  • Dry Bulb: The other thermometer, the dry bulb, remains uncovered and measures the ambient air temperature.

How it Works:

• Evaporation and Cooling: When the wick on the wet bulb is saturated with clean water, evaporation occurs. This evaporation process draws heat from the wet bulb, causing its temperature to decrease. The drier the surrounding air (lower humidity), the faster the evaporation, resulting in a larger temperature difference between the wet and dry bulbs.
• Psychrometric Table: A psychrometer table (usually provided by Brannan or found online) acts as a key component. This table correlates the temperature difference between the wet and dry bulbs with the corresponding relative humidity percentage. The table accounts for the effect of atmospheric pressure, which can vary slightly depending on your location.

Using a Brannan Wet & Dry Hygrometer:

1. Moisten the Wick: Dip the wick on the wet bulb in clean water, ensuring it’s fully saturated.
2. Place the Hygrometer: Position the hygrometer in a well-ventilated area away from direct sunlight or heat sources. Allow 15-20 minutes for the readings to stabilize, especially if the wick was dry.
3. Read the Temperatures: Record the temperature readings from both the wet and dry bulb thermometers.
4. Find the Relative Humidity: Using the provided psychrometer table, locate the row corresponding to the dry bulb temperature and then find the column that intersects with the wet bulb temperature difference. The value at this intersection point represents the relative humidity percentage.

Benefits of a Brannan Wet & Dry Hygrometer:

• Simple and Reliable: A straightforward and time-tested method for measuring relative humidity.
• Durable Construction: Brannan hygrometers are known for their quality build, ensuring long-lasting use.
• Easy to Use: Requires minimal setup and utilizes a clear measurement process with the provided psychrometer table.
• Cost-Effective: An affordable option for humidity monitoring.