Patent ID: 6973818
Filing Date: 2005-12-13
Classification: G01M

Abstract:
1. A vehicle exhaust measurement system comprising: an exhaust gas tube for receiving exhaust gas from an exhaust gas source, said exhaust gas tube adapted to be selectively blocked at an open end portion; a make-up air tube connected to and in fluid communication with said exhaust gas tube, said make-up air tube for providing make-up air; a flow meter fluidly connected to said make-up air tube for measuring make-up air flowing there through; a differential pressure sensor arranged in fluid communication with said make-up air tube and said flow meter; a temperature sensor and an absolute pressure sensor arranged proximate to said flow meter for respectively sensing the temperature and absolute pressure of make-up air flowing through said flow meter; a critical flow venturi in fluid communication with said exhaust gas tube and said make-up air tube, said critical flow venturi regulating flow at a known flow rate; and a controller connected to said differential pressure sensor, said absolute pressure sensor and said temperature sensor, wherein said controller provides a calibration procedure including drawing make-up air through said flow meter and said critical flow venturi, determining said flow rate of the make-up air through said critical flow venturi, measuring said differential and absolute pressures and said temperature, calculating a correction factor for the differential pressure, and applying the correction factor to readings from said differential pressure sensor.