General Tools Psychrometer
Psychrometers measure relative humidity by using the difference between two different thermometer readings. One reading is taken with a wet bulb and the other with a dry bulb. They are used in a variety of applications and come in different styles to meet a range of needs. The two main types of psychrometers are analog sling psychrometers and digital psychrometers.
Hygrometers and psychrometers are different from humidity meters, which measure humidity based on temperature, dew point, and relative humidity. Humidity refers to the amount of moisture present. Relative humidity is ratio of the moisture present compared to the amount of moisture needed for saturation. Hygrometers and psychrometers both calculate relative humidity, while humidity meters measure moisture content by measuring various parameters such as temperature, dew points, and more.
Psychrometer Applications
- Measurement of comfort conditions in air conditioned environments, hospital operating rooms, storage areas, and laboratories
- Tests in industrial atmospheres where high or low humidity may be critical in manufacturing processes
- School athletics -- to determine safe conditions for practice
- Target superheat calculations
- Log relative humidity over time and troubleshoot systems
- A diagnostic tool with TSH and TEET built in
Types of Psychrometers
- Analog Sling Psychrometers. This is a classic twirling design. Modern models include convenient features such as slide rule construction that quickly converts temperature to relative humidity
- Digital Psychrometers. These are highly accurate and feature data hold functions
How Does a Sling Psychrometer Work?
Sling psychrometers use two thermometers. One is a dry bulb. The other is a wet bulb, which features a cotton sock saturated with water. The user must spin the thermometers through the air at a consistent speed. Then, using the scale, find the relative humidity based on the two temperatures. Modern day digital psychrometers make this work unnecessary.
Key Features of Psychrometers to Consider
- Ability to calculate T1-T2 differential (air temperature minus external probe temperature)
and T2 – Dew Point
- Wet bulb measurements without slinging
- Slide rule construction quickly converts temperature to relative humidity
- Built-in water reservoir holds sufficient water for several hours of testing
- Thin bulb design gives fast thermal response
- Ability to measure multiple parameters such as humidity, air temperature, dew point, and web bulb temperature
- Quick response time and data hold
- Get outdoor dry bulb and indoor wet bulb for target superheat calculations
- Durability for in the field use
Fieldpiece Psychrometer