Hygrometer: real hair or synthetic hair?
“Which hygrometers are the most precise, real hair or synthetic?”
The measuring accuracy of the hygrometer depends less on whether human hair or industrially manufactured hair is used. Rather, how well the moisture-dependent change in length of the hair is transferred to the pointer axis. Human hair is therefore not necessarily more accurate or less precise than synthetic hair.
The decision between real hair and synthetic hair is primarily based on the use of the hygrometer:
Human hair hygrometers react quickly to changes in moisture and can also be used at low temperatures (application range -35… +65 ° C). They are the only mechanical hygrometers that can still be used sensibly at temperatures below 0 ° C. All other hygrometers react much too sluggishly here. However, the display stability of the human hair hygrometer is only maintained if the hair is regularly regenerated in high humidity. When used outdoors, the hygrometer is regenerated almost daily by the high night moisture. In this case, no maintenance is required. When used in a room climate, there is usually no high humidity, so the hygrometer must be exposed to high humidity at least every 3 weeks. The ‘wet pack’ method is known: the hygrometer is placed in a warm, damp cloth for at least 30 minutes. You can also simply take the hygrometer with you to the bathroom when taking a shower. Or put it outside protected from the weather overnight.
Since the maintenance effort is quite high, we recommend using a hygrometer with synthetic hair for use in the indoor climate. This can also be used at higher temperatures (application range 0… +70 ° C, with appropriate pretreatment also up to +120 ° C, for example in the sauna). The synthetic hygrometer is maintenance-free, regular moistening is not necessary. However, we recommend doing this at least once or twice a year.
The real hair hygrometer is the right hygrometer for use outdoors and in regularly high humidity. For indoor use, hygrometers with synthetic hair should preferably be used.