| 摘要 |
A passive impedance sensor uses a voltage difference 2 between a target 1 and sensor pad 3 and the changing impedance of the target measured at the sensor pad 3 as the measuring principle. As the impedance changes, either due to movement changing the coupling impedance 6 (capacitance) to the target 1 or due to electrical impedance changes in the target 1, this will induce currents into the sensor pad 3 or changes of voltage on it. A larger voltage difference will make these current or voltage changes larger thus the circuit design typically but not exclusively will maintain a high voltage on the sensor pad either by using a high bias voltage or by capacitively coupling it to a measuring amplifier 4 input and connecting the sensor pad to a high output impedance high voltage source. The sensor may be used in a tachometer for measuring turbine blade movement, position or distance. |
