The invention relates to a
mutual capacitance variation measuring method with a high precision and a high stability. The
system is composed of a switch
discharge current source, a
voltage follower and an
impulse generator. The
impulse generator generates an impulse waveform with a
fixed length of time so that a detected
mutual capacitance on a high
clock edge is charged. If a
voltage of a detected end is more than a reference
voltage, the switch
discharge current source discharges so as to reduce the voltage of the detected end until the voltage is lower than the reference voltage.<{EN4}>As for different
discharge time periods of a switch
current source caused by different detected mutual capacitances, the variation of the detected capacitances can be detected through measuring the variation of the time periods or the ratio variation of the time periods.<{EN5}>An error accumulation and mutual
elimination method is applied by the circuit so that effects of an
impact of a
voltage fluctuation, an error of a measuring
clock and an error of a detecting circuit itself on a measuring result are minimized to a lowest point. Therefore, the measuring method is great in measuring precision and stability. Because of the error accumulation and mutual
elimination, the detecting circuit does not need a circuit with the high precision, and thus a
simple circuit with the low
power consumption can be adopted to realize. As for different discharge time periods of a switch current source caused by different detected mutual capacitances, the variation of the detected capacitances can be detected through measuring the variation of the time periods or the ratio variation of the time periods. An error accumulation and mutual
elimination method is applied by the circuit so that effects of an
impact of a
voltage fluctuation, an error of a measuring
clock and an error of a detecting circuit itself on a measuring result are minimized to a lowest point. Therefore, the measuring method is great in measuring precision and stability. Because of the error accumulation and mutual elimination, the detecting circuit does not need a circuit with the high precision, and thus a
simple circuit with the low
power consumption can be adopted to realize.