- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 26 Oct 2020
A sling psychrometer holds a wet-bulb thermometer and a dry-bulb thermometer. A dry-bulb thermometer is an ordinary thermometer, whilst a wet-bulb thermometer is a thermometer that has its bulb wrapped in cloth and moistened with distilled water.
When a sling psychrometer is swung round in the air, moisture will evaporate from the wet-bulb thermometer, reducing its temperature depending on the humidity of the air it is exposed to. The higher the humidity, the lower the rate of evaporation and so the higher the temperature recorded. Wet-bulb temperatures are the same as dry-bulb temperatures at a relative humidity of 100%, but otherwise will be lower than dry-bulb temperatures due to the cooling effect of evaporation (described as wet-bulb depression).
The two thermometers should give steady-state readings after a few minutes.
A sling psychrometer can be used to determine the physical and thermal properties of moist air by using standard tables and charts. Typically it is used to determine relative humidity. Some sling psychrometers include mechanisms to allow relative humidity to be read directly without needing to refer to tables.
Psychometric charts are complex graphs that represent the dry-bulb temperature, wet-bulb temperature, relative humidity, specific volume, dew point temperature, humidity ratio and enthalpy of moist air at known atmospheric pressure. The state of moist air can be determined from any two of these properties (such as wet-bulb temperature and dry-bulb temperature which can be read on a sling psychrometer) from which all other properties can then be determined.
 Related articles on Designing Buildings Wiki
Featured articles and news
EV power sources: first you see them, then you don't!
Organisation addresses fire safety culture change and competence.
Using mathematics and psychology to make unbiased, complex decisions.
High levels of mica and pyrite found in aggregate used for Irish homes.
Organisation offers mobile app to its members.
BSRIA explores US share of 2020 VRF market.
New fire safety requirement comes into force.
Different types of bridges are meant to move.
A logical approach to handling the internal voice of self doubt.
First fashionable in the US, decorative metal has become globally desirable.
Helping communities preserve and enhance historic environments.
Creating comfortable climates despite extreme temperatures.