If that ain’t broke, don’t fix it. Psychrometers are by no means a brand-new invention and have barely adjusted in recent decades. Yet, this renowned piece the scientific devices that steps humidity is still exceptionally useful and also widely provided today.

You are watching: How to read a sling psychrometer

About Sling Psychrometers

Hygrometers measure up the family member humidity of an environment. Psychrometers space battery-free hygrometers that market a straightforward way of obtaining humidity measurements.

Psychrometers are excellent tools due to the fact that they:

Are inexpensiveDon’t need a power sourceAre portableRequire tiny maintenance, andAre exceptionally easy gaianation.nete use.

You should consider Psychrometers for environmental monitoring and also capturing field measurements if portability and low maintenance space your an important considerations. An ideal applications incorporate educational purposes, activities use, and also for measure the humidity of storage areas.

Psychrometer Design

Although every make and model will differ slightly, the an essential sling psychrometer architecture consists of 2 thermometers had within a plastic housing. A wick covers the bulb of among the thermometers. You need to soak this wick in water prior to use. This thermometer is referred to as the ‘Wet-Bulb Thermometer.’ The other thermometer stays exposed to air and also is well-known as the ‘Dry-Bulb Thermometer.’ top top the end of the thermometer housing, is a pivoting manage you use to turn the psychrometer.


Figure 1 Labelled Sling Psychrometer 

Working Principle

When water on a surface ar evaporates, it extracts heat, i beg your pardon in turn, cools a surface down significantly. In speak this, air just holds a minimal amount of water, after which it i do not care saturated, and at this point, water will certainly not evaporate as quickly.

The psychrometer architecture exploits these ethics to identify relative humidity. If the surrounding air is reasonably dry, more moisture will evaporate native the wet bulb, and also the fall in temperature will be higher. If the wait is more humid, evaporation will certainly be less, and also the autumn in temperature will certainly be lower. In a nutshell, a psychrometer identify humidity by correlating temperature movement.


Before use, soak the wet bulb wick of her psychrometer in water. When the wick is wet, organize the handle and whirl the psychrometer in the air. Whirling generates airflow about both the wet and dry bulbs. This activity allows water in the saturation wick gaianation.nete evaporate, in order to reducing the temperature of the wet-bulb thermometer. The dry pear temperature will continue to be unchanged. The temperature drop taped for the wet bulb will certainly be directly proportional gaianation.nete the quantity of water that evaporates into the air. This value called the “Wet-Bulb Depression.”.

Finding the family member humidity level is easy. Document the dry pear temperature and the known depression of the wet bulb. Put simply, Wet-Bulb Depression = Dry-Bulb Temperature – Wet-Bulb Temperature. Then usage a psychrometric chart to recognize the family member humidity that the surrounding air.

Example Video

Watch one Instrument an option Scientist take a relative humidity measurement making use of a Sling Psychrometer in the video clip below.


Figure 2 video demonstration: exactly how to take a loved one Humidity Measurement making use of the IC736700 Sling Psychrometer.


Some tools are so effective there is no allude in trying to improve them, and this is without doubt true for Sling Psychrometers. These tools are a straightforward, battery-free, and an inexpensive way to identify relative humidity.

Browse the full selection of Sling Psychrometers here.

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Want an ext information on Sling psychrometers? call one of the Instrument choice Scientists. We’re here to help! call 1300 737 871 or email .