why resistive touch screen need calibaration while capacitive touch doesn't?

The resistance screen is different in size due to the contact between the two layers of the screen at different locations. The specific contacts are obtained through calculation. Due to the batch use time of the resistance screen, etc., the resistance of the different resistance screens will be slightly different, so you are required. First locate a few points to determine the offset of the screen (that is, calibration), and each time you click on it will be based on the offset calculated from the calibration to get the exact click position.



The capacitive screen is calculated according to the capacitance of several capacitive sensors at the finger touch, and the position of the finger relative to the capacitive sensor is calculated to obtain the contact position. At this time, as long as the position of the capacitive sensor relative to the display screen is determined (because the capacitive sensor is built in In the glass of the screen, it is impossible to offset), the position of the contact can be directly obtained, so the capacitive screen does not need to be calibrated