A mechanical hygrometer indicates relative humidity directly; it is about 5 percent accurate if both temperature and humidity are held constant at room temperature. The sensing element in the hygrometer is usually a bundle of horse hair that has been put through some process to remove the oil. The midpoint of several strands of hair is connected, through a lever arrangement in the hygrometer,to an index needle. As the humidity increases, the length of the hairs increases causing the needle to move across the dial on the hygrometer. BAROMETER & WEATHER INSTRUMENTS MAX 800M ABOVE SEA LEVEL Measures the temperature on the thermometer, to the nearest degree in Celsius. The units on thermometers are clear and easy-to-read. FRENCH BAROSTAR END OF RANGE March 23rd, 2026Terri
