Systems, apparatus and methods are disclosed for coupling an averaging picot tube (APT) primary element to a process pipe. A mounting assembly mounts the APT primary element to the process pipe such that a length of the APT primary element extending into the process pipe is adjustable to accommodate different sized process pipe diameters. The mounting assembly includes a weld coupling coupled to the process pipe over an opening in the process pipe and having the APT primary element extending therethrough into the process pipe. An extension pipe nipple is connected to the weld coupling and has the APT primary element extending therethrough such that a transition between a neck section and a sensor section of the APT primary element is positioned inside the extension pipe nipple. A union component, a ferrule, and a cap keep the APT primary element in the mounted position and form a process seal.