Coordinate detecting device and method

A coordinate detecting method applied to a coordinate detecting device including:

• a resistive film disposed on a quadrangular substrate made of an insulating material;
• a power source configured to apply a voltage to the resistive film;
• four electrodes including a first electrode, a second electrode, a third electrode and a fourth electrode, each of which is connected to the power source and individually disposed in one of four corners of the resistive film;
• four switches including a first switch which is disposed between the power source and the first electrode, a second switch which is disposed between the power source and the second electrode, a third switch which is disposed between the power source and the third electrode, and a fourth switch which is disposed between the power source and the fourth electrode;
• four ammeters including a first ammeter which is connected in series to the first switch and configured to measure a first current flowing through the first electrode, a second ammeter which is connected in series to the second switch and configured to measure a second current flowing through the second electrode, a third ammeter which is connected in series to the third switch and configured to measure a third current flowing through the third electrode, and a fourth ammeter which is connected in series to the fourth switch and configured to measure a fourth current flowing through the fourth electrode;
• and
• a grounded conductive film configured to detect coordinates of a contact point on the resistive film when the conductive film is brought in contact with the resistive film;
• the coordinate detecting method comprising:
• a first measurement step of closing only the first switch, applying the voltage to the resistive film, and causing the first ammeter to measure the first current;
• a second measurement step of opening the first switch, then closing only the second switch, applying the voltage to the resistive film, and causing the second ammeter to measure the second current;
• a third measurement step of opening the second switch, then closing only the third switch, applying the voltage to the resistive film, and causing the third ammeter to measure the third current;
• a fourth measurement step of opening the third switch, then closing only the fourth switch, applying the voltage to the resistive film, and causing the fourth ammeter to measure the fourth current;
• a first calculation step of calculating resistances, each of which is individually obtained based on one of the first current, the second current, the third current and the fourth current;
• and
• a second calculation step of calculating, based on the calculated resistances, the coordinates of a single contact point or two contact points on the resistive film.