The term ‘ cosh mL” should be as large as possible. The behavior of the cosh function is shown in 8.35. Since the hyperbole disige shown be to maximize the value of the product mL, or, In general, the thermal conductivity of a tempwrature probe and the convertion coefficient are not desing parameters. Thus, two important conclusions are that the probe should be as small in diameter as possible ,and should be inserted as possible into the measuring environment aeay from the bounding surface to make L lage. A small diameter increases the ratio of the perimeter p to the cross-sectional area. For a circular cross section, this ratio 4/D, where D is the diameter. A good rule of thumb based on Equation 8.27 is to have an ……….. for negligible conduction error.