Method and apparatus for detecting operational failure of a digital accelerometer

U.S. Patent Number: 5737961

Abstract: An apparatus includes an accelerometer (24) for providing an analog acceleration signal indicative of crash acceleration. A sigma-delta A/D converter (26) is operatively connected to the accelerometer (24) for providing a pulse-width-modulated gate enable signal (GES) with a value indicative of the acceleration signal. The GES signal is ANDED with a clock signal to produce a pulse-density signal (CNT) indicative of the acceleration signal. A monitoring circuit determines (i) whether at least one pulse-density signal occurs when a gate enable signal is HIGH (FLAG 1), and (ii) whether the pulse-density signal occurs when the gate enable signal is LOW (FLAG 2). Other embodiments test to see if the gate enable signal is either full scale ON (FLAG 3) or full scale OFF (FLAG 4) by using a second crash sensor (64). Timing circuits (302, 316) are used to ensure that the pulse duration of at least one pulse-width modulated gate enable signal is greater than predetermined value within a predetermined time period.

Inventors: Hanisko; John Cyril P. (Southfield, MI); Munch; Carl A. (Troy, MI)

Assignee: TRW Inc. (Lyndhurst, OH)

Application Number: 08/622,705

Issued: 1998-04-14

Expired: 2006-04-14

Classes: 73/1.38 ; 73/1.39; 73/514.35

Field of search: 73/1D,510,514.01,514.16,514.32,514.35,1.38,1.39

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