A wireless power transmitting device transmits wireless power signals to a wireless power receiving device. To detect foreign objects, the wireless power transmitting device has an array of temperature sensors. The array of temperature sensors may include temperature sensor components such as temperature sensitive thin-film resistors or other temperature sensitive components. A temperature sensor may have thin-film resistors formed on opposing sides of a substrate. The thin-film resistors may be formed from meandered metal traces to reduce eddy current formation during operation of the wireless power transmitting device. Signal paths coupling control circuitry on the wireless power transmitting device to the array of temperature sensors may be configured to extend along columns of the temperature sensors without running along each row of the temperature sensors, thereby reducing eddy currents from loops of signal routing lines. Some temperature sensors may have multiple components coupled to a common temperature sensing pad.