Your Philips Humidifier is equipped with a built-in humidity sensor. Please follow the steps below to check the humidity sensor:
Remove the cover of the air quality/humidity sensors of your Philips Humidifier and then gently blow moist air into the humidity sensor at the back of your humidifier (please see the image below).
After a few seconds, the "current humidity" indication of your humidifier should change in the centre of the control panel on the top of the device.
If the initial "current humidity" indication of your humidifier is already 60%, the indication cannot show an even higher humidity level when you blow moist air towards the sensor.