A method and apparatus is described for determining a parameter of interest of a formation fluid. Preferred coagulants are cationic or amphoteric polymers. The device characteristics may be controlled and a memory device with improved device characteristics may be provided. The third conductive member includes an inner portion positioned on an inner side of the partition wall, and an outer portion extending from the inner portion toward an outer side of the partition wall and capacitively-coupled with the second conductive member. Accordingly, the present invention reduces the high-current region and the power consumption of the device while providing the required hystersis on the input.