Abstract: A current sensor includes a core arranged around a conductor, a sensing element arranged on the core and configured to generate an output variable dependent on a magnetic field in the core, and a measuring unit configured to detect the output variable and to derive a measured value of the current. The current sensor further includes a test coil arranged around the core and a test current generator connected to the test coil. The test current generator is configured to generate a test current signal of a specified amplitude and to output the test current signal to the test coil. The current sensor further includes a testing unit connected to both the measuring unit and the test current generator and configured to output information regarding the current sensor. The information is output as a test signal dependent upon comparing a first and a second measured value.