Hygrometer with natural hair

The illustration shows the hair hygrometer in the first brochure from Feingerätebau Kurt Fischer in Drebach. A relic from the old days? More than 50 years later, the FISCHER classic is the test winner in STIFTUNG WARENTEST issue 3/2003!
The FISCHER instrument was the only hygrometer tested to achieve a rating of VERY GOOD (1.3) for HUMIDITY MEASUREMENT. Measurement accuracy, hysteresis, and response speed were assessed. The hair hygrometer also received the best rating of GOOD (1.7) for HANDLING .

Hygrometers are used to measure relative humidity and are based on the hygroscopic properties of natural hair or synthetic fibers, which change their length with changes in humidity.

While natural hair can be used at temperatures below 0 °C, hygrometers with synthetic fibers react extremely slowly in this temperature range and are therefore not recommended for outdoor use.

Hair hygrometers require regular regeneration (every few weeks); this is generally not necessary for hygrometers made of synthetic fibers.

The main features of the natural hair hygrometer are:

• Can be used below 0 °C,
• With sufficient natural fluctuations in relative humidity, the natural hair regenerates itself,
• low hysteresis (1,3),
• high reaction speed.
• good handling (1.7)
• high reliability
• easy operation