Whirling Hygrometer

A Whirling Hygrometer, also known as a Sling Psychrometer, is a portable instrument used to measure relative humidity (RH) by comparing the readings of two alcohol-filled thermometers—one dry bulb and one wet bulb.

The instrument is rotated (whirled) through the air using its handle. Airflow over the wet bulb causes evaporation, lowering its temperature. The difference between the dry bulb and wet bulb temperatures is used to calculate relative humidity using a psychrometric chart or table.

Alcohol is used because it is non-toxic, environmentally safer than mercury, and performs well at low temperatures, making it suitable for a wide range of environmental conditions.

No. Relative humidity is determined by comparing the wet and dry bulb readings using a psychrometric chart, table, or calculator.

For accurate readings, the hygrometer should typically be whirled for 20–30 seconds, or until the wet bulb temperature stabilizes.

Replace the wick whenever it becomes dirty, damaged, or loses its ability to absorb water effectively.

Our Whirling Hygrometers are manufactured using premium-quality materials and precision alcohol-filled thermometers to provide dependable temperature and humidity measurements. They are durable, easy to operate, maintenance-friendly, and ideal for professional, laboratory, educational, and industrial environmental monitoring applications.