Delay has been one of the critical factors affecting control performance of a wireless networked control system. It leads to the instability of the system. Network induced delay awareness is important for investigating the delay effects on the system. There are several direct and indirect ways to measure delays in a network. This paper concentrates on a direct delay measurement approach between WirelessHART controller and its plant. Upstream and downstream delays are measured by calculating the difference at timestamps between two consecutive received messages at the controller and at the plant respectively. The measured roundtrip delay is used to study delay effects on the control system's performance. © 2016 IEEE.