A device for attaching to an electric power line conductor includes an electrically conductive housing with an opening for accepting the power line conductor and configured to be grounded to the power line conductor. At least one magnetic core is configured to surround the power line conductor and power a power supply electronics module. An ambient temperature measuring assembly is mounted inside and near the bottom of the electrically conductive housing. The ambient temperature measuring assembly is thermally insulated from the housing for thermally separating the ambient temperature measuring assembly from the housing.