Abstract
A microscale sensor for an accurate measurement of wall shear stress is developed using the microelectromechanical system fabrication technique. The sensor uses a thin metal film whose temperature is kept constant using a constant temperature circuit, and the wall shear stress is determined by measuring the heat flux from this film. The circuit consists of a Wheatstone bridge and an integrated circuit. For sensor calibration, an instrument is built using a circular cylinder and a flat plate. When the cylinder is rotated above the flat plate, a flow with a constant shear rate is produced on the flat plate. A calibration test is conducted under several conditions of the wall shear stress. Results of the calibration tests show that the output voltage of the constant temperature circuit increases with the wall shear stress. Moreover, the square of the output voltage is proportional to the cube root of the wall shear stress, as predicted theoretically.
