This invention is related to a microfabricated microelectromechanical systems (a.k.a. MEMS) silicon thermal mass flow sensor integrated with a micromachined thermopile temperature sensor as a flow inception detection sensor. The micromachined thermopile sensor is used to detect the inception of mass flow and therefore to trigger the operation of mass flow sensor from its hibernating mode. By this method, the battery-operated flow speed measuring apparatus can save great deal of electricity and significantly extend the life span of battery. A new design of micromachined thermopile sensor with serpentine shape is used to reduce the complexity of microfabrication process and to increase the flexibility and options for material selection. In order to enhance the sensitivity of the thermopile temperature sensor, a method to maximize the quantity of the junctions is provided as well.