###### Abstract  
It is extremely important to gather the viscosity behavior of fluids accurately for industries and academia. There is no better method than viscosity measurement to detect changes in the specific characteristics of the materials. However, viscosity measurement is indeed a very sensitive process. In nature, fluids are involved in widely various containers, and they are affected by serious temperature deviations. It is a necessity for viscometers to have the capability to obtain accurate data from all types of containers of fluids even in serious temperature variations in order to understand the natural phenomena inside the fluids. Conventional viscometers mainly neglect the effect of sudden temperature deviations inside the fluids, or they need to use very expensive water bath systems that stabilize the temperature around the test fluids, which is not feasible at all. In this research, the effects of non-uniform temperature fields are analysed detailly to confirm that even in extremely limited amounts, serious viscosity and temperature deviations may occur. Experiments were performed in two parts. The first part was conducted using several thermocouples with different test fluids to find out the effects of thermal conduction and convection. For the second part, particle image velocimetry (PIV) was utilized to comprehend the flow movement within the test fluids. It was shown that even for small volumes and even in very controlled environments, an almost 35% viscosity measurement error (_VME_) occurs. Finally, as a solution to this problem, a new non-dimensional parameter called the Akpek number was proposed. The Akpek number enables the estimation of _VME_s in any possible case. _VME_ is a very crucial obstacle that has urgency to be illuminated by researchers and scientists to improve fluid characteristics. The main goal of this research is to illuminate the importance of this problem and offer a potential solution. The final results are supported by experimental data and numerical simulations using OpenFOAM. v 2023 202  
safety [6]. In a similar manner, blood viscosity is utilized to comprehend cardiovascular diseases in medicine [7; 8]. Therefore, understanding and defining fluid quality via viscosity assessment is imperative for ensuring optimal performance and reliability across diverse industrial sectors. There is no better method than viscosity measurement to detect changes in the specific characteristics of materials [9]. Viscosity measurement is a crucial aspect of fluid characterization, but it comes with its fair share of challenges. One of the primary difficulties lies in accurately measuring viscosity across a wide range of fluids, from low-viscosity liquids to highly viscous substances. Traditional methods like capillary viscometry and rotational viscometry may struggle to provide precise results for non-Newtonian fluids, which exhibit complex viscosity behaviors under different shear rates [10]. Moreover, the presence of suspended particles or bubbles in the fluid can further complicate viscosity measurements, leading to inaccurate readings [11]. In addition to these challenges, heat transfer effects can significantly impact viscosity measurements. Temperature changes can alter a fluid's viscosity, and maintaining a consistent temperature throughout the measurement process is essential to ensure accurate results [12]. Non-isothermal conditions can induce temperature gradients within the fluid, leading to variations in viscosity readings. Researchers must carefully consider the impact of heat transfer on viscosity measurements and implement appropriate temperature control techniques to minimize potential errors. Addressing these difficulties and understanding the effects of heat transfer is crucial for obtaining reliable and meaningful viscosity data across various fluid systems. In normal conditions, heating from the surrounding environment causes heat transfer [13; 14; 15]. The three fundamental modes of heat transfer are conduction, convection, and radiation [16].