Temperature gradient sensing in portable electronic devices

An electronic device housing encloses a temperature sensing system including a temperature sensor and a differential temperature probe. The differential temperature probe includes a flexible substrate defining two ends. A first end is thermally coupled to the temperature sensor and a second end is thermally coupled to a surface, volume, or component of the electronic device. The temperature probe is an in-plane thermopile including a series-coupled set of thermocouples extending from the first end to the second end. A temperature measured at the temperature sensor can be a first measured temperature and a voltage difference across leads of the differential temperature probe can be correlated to a differential temperature relative to the first measured temperature. A sum of the differential temperature and the first measured temperature is a second measured temperature, quantifying a temperature of the second end of the differential temperature probe.