| 摘要 |
A device (400) for sensing a binary signal (450) is provided. The device comprises means (410) for measuring a signal level of the signal, means (420) for determining whether the measured signal level is "low" or "high", means (430) for providing a variable input impedance, and means (440) for controlling the input impedance in response to the measured signal level. The variable input impedance may be provided by way of a transistor (T) and a resistor (R), and by controlling the duty ratio of the transistor using pulse width modulation. Preferably, the input impedance is controlled to be low for low signal levels and to be high for high signal levels, which results in a more reliable sensing of binary signals. The device may be used for detecting the state of contact transducers suffering from parasitic resistances caused by moist and/or polluted environments. Further, a method of sensing a binary signal is provided. |
