It is shown that there exists an optimal spacing of thermo-sensors in the determination of the experimental heat transfer coefficient of a fluid flowing over a plate. The problem is considered as an inverse heat transfer problem with long thin fin model. The heat transfer coefficient of the fluid is estimated from simulated steady-state temperature measurements along the plate. It is shown theoretically that the inner product of the sensitivity vector, J(T)J, should be maximum and the group m n d should be. equal to 1.692 to obtain the most accurate coefficients, where m is a system parameter containing heat transfer coefficient h, n is the number of thermo-sensors and d is the sensor spacing. These results are also verified by simulated experiments.