(1) Why the LED does not light up ?
R:The application provides the power supply through one of the two audio channels. The correct level of the supply voltage is indicated by the LED turned on. If this fails, here are some of the possible causes (and remedies):

- Your smartphone complies with the OMTP standard (use an adapter/converter CTIA/OMTP)

- Audio channels L/R are reversed (change the option in the settings menu of the app)

- The sound volume is too low (turn up the volume in the settings menu of the app and/or using the volume buttons of the device)

(2) When should I calibrate the sensor ?
R: The first time the application is connected to the sensor SS03, you must calibrate it by inserting the values of the two coefficients specified in the first page of the manual. A subsequent calibration may be required after a long time especially in case of intensive use of the probe or every time you have doubts about the accuracy of the measurement. In this case it is suggested to perform a calibration with self-learning by following the instructions in the Info menu of the application.

(3) How much pressure must be exerted on the probe ?
R: The probe must be applied on the area of measurement so that the moveable head comes into contact with the skin (the surface must be free from hair or other obstacles). It is advisable to apply pressure just sufficient to put in contact with the skin also the metal edge of the probe. Higher values of pressure can deform the skin tissue and alter the content of surface hydration. For more tips and advices, please consult the Info menu of the application.