With the rise of Industry 4.0, wireless communication is a tendency in industrial environments, saving resources and enabling the addition of new applications when compared to their wired counterparts. In this context, the WirelessHART and ISA100.11a specifications are emerging as solutions for the last mile connection. Despite their high degree of applicability, due to the nature of its technical challenges (reliability, energy consumption, fault tolerance, ensuring constant delays), industrial wireless networks used, in the majority of applications, for monitoring processes. Given the aforementioned and the conservatory tendency of the industry, the demand for evaluation and assured reliability tools on Wireless Networked Control Systems (WNCS) is imminent. Aiming to enlighten and demystify the use of wireless technology on the control loops in the industry, this work presents an overview of WNCS and a practical experiment of evaluation that enables the analysis of the behavior of typical WirelessHART and ISA100.11a networks in process control by controlling the level loop of a process station through a PID algorithm implemented in a host application. The conducted control study used the Dust-Networks SmartMesh WirelessHART Starter Kit and Nivis ISA100.11A Integration kit to establish the networks, allied to Emerson's 3051S and Yokogawa's EJX110 pressure transmitters, and assures reliability and efficiency for WNCS applications.