A humidity measuring device connectable to an electronic measuring apparatus that is provided with: at least a first terminal and a processing module, which is configured to determine the humidity based on the measurement voltage on said terminal, the humidity measuring device comprises: a humidity sensor that is configured to provide an electrical pulse signal and to modulate the duty cycle of said electrical pulse signal based on the detected/measured humidity; and a first electronic stage, which is electrically connected to said humidity sensor for receiving said electrical pulse signal and is configured to vary the measurement voltage on said first terminal of said measuring apparatus based on the duty cycle of said electrical pulse signal, said first electronic stage comprises: a resistor (8R9), and an electronic switch device (8Q4) that is connected to said resistor (8R9), wherein said humidity sensor controls the electronic switch device (8Q4) by means of the electrical pulse signal to vary the equivalent resistance between said first terminal and a second terminal based on the detected/measured humidity; wherein said processing module is configured to detect a measurement voltage variation based on the variation of said equivalent resistance. at least a first terminal and a processing module, which is configured to determine the humidity based on the measurement voltage on said terminal, the humidity measuring device comprises: a humidity sensor that is configured to provide an electrical pulse signal and to modulate the duty cycle of said electrical pulse signal based on the detected/measured humidity; and a first electronic stage, which is electrically connected to said humidity sensor for receiving said electrical pulse signal and is configured to vary the measurement voltage on said first terminal of said measuring apparatus based on the duty cycle of said electrical pulse signal, a humidity sensor that is configured to provide an electrical pulse signal and to modulate the duty cycle of said electrical pulse signal based on the detected/measured humidity; and a first electronic stage, which is electrically connected to said humidity sensor for receiving said electrical pulse signal and is configured to vary the measurement voltage on said first terminal of said measuring apparatus based on the duty cycle of said electrical pulse signal, said first electronic stage comprises: a resistor (8R9), and an electronic switch device (8Q4) that is connected to said resistor (8R9), wherein said humidity sensor controls the electronic switch device (8Q4) by means of the electrical pulse signal to vary the equivalent resistance between said first terminal and a second terminal based on the detected/measured humidity; wherein said processing module is configured to detect a measurement voltage variation based on the variation of said equivalent resistance. a resistor (8R9), and an electronic switch device (8Q4) that is connected to said resistor (8R9), wherein said humidity sensor controls the electronic switch device (8Q4) by means of the electrical pulse signal to vary the equivalent resistance between said first terminal and a second terminal based on the detected/measured humidity; wherein said processing module is configured to detect a measurement voltage variation based on the variation of said equivalent resistance.