We report a development of a micro viscosity sensor, named η-MEMS, which is manufactured by processing technology of micro electro mechanical systems. The small package of the sensor-holder made from stainless steel has a size of a USE memory. The viscosity can be easily measured by dipping the sensor holder into the sample liquid directly. The basic shape of the viscosity sensor is double spiral. In the present study, we evaluated the performance of the USB memory sized holder and new signal processing method. In the new system, the viscosity of the liquid is obtained by detecting the amplitude of the vibration of the sensing spiral. The performance of the holder and the system were evaluated. In experiment with DC bridge amplifier, electromagnetic noise disturbed the appropriate signal processing. On the other hand, AC bridge amplifier decreased the noise and detected the reasonable signal. Finally, The theoretical relationship between the amplitude and viscosity is verified.