The application of current and voltage sensors in the electric power network is exhibiting considerable growth in the US. Several utilities have deployed large number of post insulator type current and voltage sensors on the distribution feeders for initiatives such as Volt-VAR Optimization (VVO) and Conservation Voltage Reduction (CVR). Due to the lack of a stand-alone standard for sensors in IEEE, every vendor has a slightly different way to test the accuracy of these sensors. Furthermore, we have noted a mismatch between single-phase test results in the laboratory and performance in actual 3-phase outdoor field installations. In this paper we explore the reasons for aforementioned performance gaps and propose specific additional tests that should be carried out to get a full understanding of the accuracy behavior of the sensors.