Flow sensor, a manufacturing method and a determination method of the resin-made structures

Use the cover material appearance can sense the abnormal temperature and time history for flow sensor in a high temperature environment, when used in the time and the abnormal state product delivery also guarantees can cover material laser welding quality by visual inspection It is to provide a flow sensor which had. A housing, a cover, a circuit chamber incorporating a sealed wiring portion therebetween, a flow sensor fluid as the sensor target is provided with a sub-passage that passes through the junction formed in the housing, the cover and a joint portion formed on an inner surface joined by laser welding, the main material of the cover is a crystalline resin, and contains a non-crystalline alloy material, the cover and natural colors.