Wireless instrumentation has been used in networked control systems (NCS), generating a control architecture with wireless information traffic. However, there are some features that can influence the design of the control system, such as the packet loss rate or the package delivery rate. This work proposes to evaluate the influence of the packet delivery rate on the variation of the steady state error of a level control. A wireless networked control system architecture with ISA 100.11a technology was implemented to perform the tests and data collection. The results show that there is a direct correlation of packet loss with the controller error.