A sensor device includes a first and second Micro-Electro-Mechanical (MEM) structures. The first MEM structure includes a first heating element on a first layer of the first MEM structure. The first heating element includes an input adapted to receive an input signal. The first MEM structure also includes a first temperature sensing element on a second layer of the first MEM structure. The second MEM structure includes a second heating element on a first layer of the second MEM structure and a second temperature sensing element on a second layer of the second MEM structure. An output circuit has a first input coupled to the first temperature sensing element and a second input coupled to the second temperature sensing element.