We have been researching about a control system for stabilizing liquid surface vibration by moving the liquid (water) tank.. Until now, not so long (about 10cm) cylindrical sensor has been used to check the possibility of the effectiveness of the sensor utilizing only capacitance component change of this type sensor. However, in a practical liquid tank system longer cylindrical liquid-height sensor is needed and then it was a problem that the output voltage of the sensor was gradually saturated. The reason is considered to be caused by approximating water level change by only capacitance component change. So, the characteristic of each component of the sensor wan analyzed. As a result, the model and the equivalent circuit of the sensor were established. Then, new method circuit detecting the current of the sensor was proposed because admittance characteristic of the sensor wan linear in water level, and so the sensor measuring range was expanded. Also, it was confirmed to be able to apply the circuit to the vibration control system. In consequence, the proposed new method can be used as a large amplitude vibration sensor.