Classic, mechanically-based hygrometers, although less widely used now, include wet/dry bulb hygrometers (also known as psychrometers), and hair tension hygrometers, which rely upon a single (hygroscopic) hair or fibre, under tension, whose length varies with moisture levels.

However, most modern models available on the market today are electronic digital instruments, which measure humidity by means of capacitive or resistive sensors. These digital devices offer clear displays with reliable and consistent performance, and are typically compact, hand-held or benchtop units with minimal footprint. They may also be available in combination with temperature, timer and alarm functionality, or with externally-corded probes and wireless radio-signal connectivity for remote monitoring and data logging. Many operate over a wide temperature range of -5° to +50°C, with a typical measurement range of 0 to 95% Relative Humidity (RH).

Both classical and electronic hygrometers are available, many with additional functionality, to measure humidity in a range of environments and applications.