123TMS hygrometer and thermometer, 87x84mm, brand Fischer, Germany. Brass housing. Hook for hanging on the wall. It is a precise product of the German professional company Fischer that has been building barometers, hygrometers and thermometers for many years. Material: aluminum, brass Hygrometer measuring accuracy: ± 5% rh (20 ... 100%), + 1 graduation scale Thermometer measuring accuracy: ± 1 K, + 1 graduation scale A person feels comfortable at a temperature between 18 and 22 degrees Celsius and at an air humidity of 35-65%. We should ensure proper air humidity. It is a matter of our health and well-being. It should be remembered that the air humidity measured with a hygrometer located in the house will only correspond to the humidity inside. Outside, large jumps in humidity occur during the day. Moisture sensor - synthetic fiber, which, unlike the use of hair, guarantees excellent measurement accuracy without the need for servicing the device. Acceptable measurement accuracy +/- 5% - ASSMANN ASPIRATION PSYCHOMETER is the appropriate comparator. It is important that the device is operated in a suitable place, not too close to a heat source and not, e.g. in a draft. For the purpose of the correctness test, the method of wrapping the device in dry material is also used. After about half an hour, the device will show the actual humidity with an accuracy of 95-98%. It is worth mentioning that Fischer hygrometers are recognized, among others, by archives and libraries, i.e. institutions where the conditions for storing documents or book collections are very restrictive.