| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the reliability and certainty of the device by using an absolute value detection type level measuring circuit as a circuit which measures a finger touch position and then reducing detection deviation in touch position into a problem-free range even when multiple devices are used nearby at the same time. SOLUTION: A vibration voltage applying circuit 6 supplies a passing current to its circuit ground even when not selected by an analog multplexer(MUX) 8 to always hold input characteristics under certain conditions. An AC signal current having passed through the MUX 8 is processed by current/voltage conversion, band-pass filtering, AC-signal level demodulation, etc., and applied to an A/D converter 10. From its respective digitized data, a processor (CPU) 11 calculates the position of a touch on the surface of a panel 1 with a finger of a human body 2. At this time, an absolute value detection type AC signal level demodulating circuit is not affected by the phase shift of the AC signal. Therefore, deviation in the ratio of respective signal levels is eliminated to eliminate deviation in calculated position.</p> |
