FIELD: measuring equipment.SUBSTANCE: group of inventions relates to measurement equipment, in particular to relative humidity measuring devices and methods, more particularly to a relative humidity sensor, to relative humidity measuring method and to relative humidity measuring system. Relative humidity sensor comprises at least a sensor element configured to measure a relative humidity value, convert said relative humidity value into a digital signal corresponding to the relative humidity value and send the digital signal to the microcontroller input, microcontroller configured to receive said digital signal from said sensor and convert said digital signal into a resistance value, wherein the said resistance value corresponds to a non-negative temperature value in the range of 0 to 100 degrees, assign each said resistance value a relative humidity value, wherein the said relative humidity value corresponds to a relative humidity value in the range of 0 to 100 percent; and send said resistance value, to whic
