A simple viscometer is designed and fabricated to characterize rheological behaviors of non-Newtonian fluids, and a novel viscometer equation suitable for the viscometer is developed. Various additives such as ethanol, acetic acid, salt, baking soda, sucrose, and carboxymethyl cellulose (CMC) sodium salt are used to modify rheological properties, atomization, and coating strength of polyethylene oxide (PEO) aqueous solutions. The main objectives of this study are to examine effects of additive amounts such as ethanol, acetic acid, salt, baking soda, sucrose, and CMC sodium salt on non-Newtonian behaviors of PEO aqueous solutions, to design a simple viscometer for pseudoplastic fluids, and to develop a viscometer equation suitable for the viscometer in determining fluid consistency index and flow behavior index of PEO aqueous solutions. Non-Newtonian characteristics of PEO aqueous solutions are extensively investigated in terms of the additive amounts such as ethanol, acetic acid, salt, baking soda, sucrose, and CMC sodium salt with the viscometer and its viscosity equation. Sucrose aqueous solution is used as a reference/calibration liquid for the viscometer.