I have got the same problem with my u7142 unit. This most probably means that the hygrostat inside is either broken or it has been heavily covered with the "white dust" in case the demineralization cartridge has not been changed for a long while. To resolve it you have two options: either clean the humidity sensor or replace it. The sensor is at the bottom of the front panel, so you need to disassemble the front panel only, no need to open the whole unit (note that there are 2 screws at the bottom holding the front panel also). You need to get the sensor out from the printed circuit to open the cover and clean the surface of the sensor with something (blowing air does not help; you need physically touch the surface with something). If it does not help then you can go for the second option to replace the sensor, the type used in the unit is SYH-1. It is not a pricy element so you may go straight to the replacement if you find a shop nearby to buy it. I have simply replaced the sensor and now the unit is showing the proper humidity value and adjusting the steam automatically again.
Humidifiers existence is notable because they have been helping many people to keep themselves away from dry air problems. They work perfectly to keep the humidity inside your house. With the fresh and friendly air, you and your family will be away from problems like cracked lips, nose bleeding, dry skin, and many other related conditions. Although there are many types of humidifiers sold in the market, basically the function is to emit water vapor into your indoor space to maintain the recommended level of humidity. When operated successfully, the humidifiers can alleviate all the problems mentioned. So you will not meet any of the dry air related problems when having a humidifier which is operated properly. However, you want to make sure that the air inside your home is free from pollutants. In order to prevent contaminants and pollutants from entering your house, you need to properly clean your device. While you clean the device, you also need to check the device's condition as well.