A sensor circuit for detecting a current supplied to a non-linear light-emitting diode (LED) and for producing a current reading dependent on temperature. The sensor circuit comprises first and second serially interconnected resistors also connected in series with the LED, and a temperature-dependent impedance connected in parallel with one of the first and second resistors. At least a portion of the current through the LED flows through the sensor circuit to enable the first and second serially interconnected resistors and said temperature-dependent impedance to produce a variable voltage signal representative of the current through the LED and dependent on temperature.