Accurately measuring the total temperature of a high-speed fluid flow is a challenging task that is required in many research areas and industry applications. The difficulty in total temperature measurement generally stems from attempting to minimize measurement error or accurately predict error so it can be accounted for. Conduction error and aerodynamic error are two very common sources of error in total temperature probe measurements. Numerous studies have been performed in prior literature to account for simple cases of both errors. However, the impacts of a mounting strut and freestream flow angle on conduction error and aerodynamic error have not been previously modeled. Both of these effects are very common in gas-turbine applications of total temperature probes. Therefore, a fundamental study was performed to analyze the impact of mount interference and freestream flow angle on a probe's conduction error and aerodynamic error. An experimental study of aerodynamic error was performed using strut-mounted thermocouples in a high-speed jet at Mach numbers ranging from 0.25-0.72. This study showed that a strut stagnation point can provide aerodynamic error reductions and insensitivity to approach Mach number. An off-angle experimental study of conduction error was also performed using strut-mounted thermocouples at pitch angles ranging from -30° to 30°. High-fidelity Computational Fluid Dynamics (CFD) simulations with Conjugate Heat Transfer (CHT) were performed in conjunction with the experiments to provide key heat transfer information and flow visualizations. It was identified that unshielded total temperature probes have reduced conduction error at off-angles, but are sensitive to changes in the freestream flow angle. A low-order method was developed to account for mount interference and flow angle effects. The developed low order method utilizes a local Mach number for aerodynamic error predictions and a local Reynolds number for conduction error predictions. This developed low-order method was validated against experiment and 3D, CFD results, and was shown to accurately capture flow angle trends, mount interference effects, and the impacts of varying probe geometry. / Master of Science / Accurately measuring the total temperature of a high-speed fluid flow is a challenging task that is required in many research areas and industry applications. Many methods exist for measuring total temperature, but the use of thermocouple based probes immersed into a flow remains a common and desirable measurement technique. The difficulty in using thermocouple based probes to acquire total temperature stems from attempting to minimize or accurately predict the probe’s measurement error. Conduction, convection, and radiation heat transfer between the fluid flow and probe create challenges for minimizing measurement error so that the accurate total temperature can be obtained. Numerous studies have been performed in prior literature to account for simple cases of each error source. However, there are many complex, practical applications in which the influence of each error source has not been studied. The impacts of a freestream flow angle and the total temperature probe’s mounting structure have not been previously modeled. Both of these effects are very common in gas-turbine applications of total temperature probes. This Thesis will present a fundamental study analyzing the impact that freestream flow angle and a probe’s mount have on a total temperature probe’s measurement error. The influence of conduction and convection heat transfer was studied experimentally for numerous probe geometries, and the impacts of a mounting strut and freestream flow angle were analyzed. A low-order method was developed to predict conduction error and aerodynamic error for total temperature probes in offangle conditions with the presence of mount interference. The developed low-order method was shown to accurately capture the effects of a mounting strut, varying probe geometry, and varying flow angle. Additionally, the low-order method was validated against experimental and 3D, CFD/CHT results.