'From nist to under the hood': flow measurement traceability at ford

摘要

The calibration of the intake air mass flow sensor in an automobile is traceable to NIST through the following four steps. 1. A primary flow standard is traceable to NIST by mass and time standards. 2. Production test chambers that are calibrated against the primary flow standard. 3. A quality control test chamber that is also calibrated against the primary flow standard. 4. Asensor that is used to measure the mass flow of engine intake air. This paper describes the four step process with the objective of estiamting the uncertainty associated with the sensor installed under the hood. Discussions are made regarding the impact of hardware, environmental conditions, process complexity and cost issues for each of the fours steps.