| 摘要 |
<p>PURPOSE:To obtain precisely the coordinates of the input position of an electric pen for input by connecting diode groups to two opposite sides and other two sides of one resistance sheet, and connecting current detection parts to the opposite sides. CONSTITUTION:Diode groups 55-58 are connected to four sides 51-54 of the resistance sheet with uniform surface resistance, and inverted input terminals 71- 74 of operational amplifiers 59-62 are connected to the opposite sides. When the tip 81 of the electric pen 79 is put close to a point P on the resistance sheet 50, those are coupled with each other electrostatically and an AC current flows. This current flows through the diode groups 55-58, so it changes the route according to the direction. The values of currents flowing through lead lines 67-70 are obtained to find the coordinates of the point P from a simple expression. Output voltages of the operational amplifiers 59-62 are proportional to currents flowing through the lead lines 67-70. A processing circuit 86 switches output voltages of the operational amplifiers 59-62 through an analog multiplexer and convert them from analog to digital, and the digital voltages are inputted to the multiplexer to calculate the coordinates of the point P.</p> |
