Abstract: A sensor that includes a first resistor, a second resistor, a first circuit, and a second circuit. The first and second resistors each has a resistance that varies in response to a change in a physical property. The first circuit is electrically coupled to the first resistor and sets the resistance of the first resistor. The second circuit is electrically coupled to the second resistor and adjusts the resistance of the second resistor to equal the resistance of the first resistor. A processing circuit may be coupled to the first and second circuits to measure a difference in an amount of energy provided by the first and second circuits to the first and second resistors, respectively.