In this paper we investigate the observation problems for a class of nonlinear Lipschitz systems, subject to network constraints. In order to address this problem, an impulsive observer is designed, making use of the event–triggered technique in order to diminish the network usage. The proposed observer ensures practical state estimation. The output sampling is done on a periodic basis, but the data transmission is regulated by an event–triggering mechanism. The performance of the observer is tested in simulations of a flexible joint.