Patent ID: 6885923
Filing Date: 2005-04-26
Classification: F05B,G05B

Abstract:
1. A signal fault detection system useable in electrical control sensors for shaft speed signal frequency change rate tests, detecting intermittent or “in-range” failures of the signal rate of change, comprising: means for measuring frequency of a shaft speed signal; means for calculating a rate of change (time derivative) of the measured signal; means for estimating a short-term variance of the measured signal rate of change using the equation: Var[x]=E[x−E(x)] means for estimating the short-term variance Var[x]=E[x means for comparing the estimated variance with a predefined variance limit for a predefined amount of time; and means for deeming the measured signal invalid, if the estimated variance exceeds the predefined variance limit for the predefined amount of time.