Method for testing airbag system release circuit

Claim 1

A method for testing a circuit for releasing an airbag comprising an accelerometer, an integrator for receiving a signal from the accelerometer, said integrator being conditioned by a signal having a first threshold value such that said integrator integrates a signal received from said accelerometer only if said accelerometer signal exceeds said first threshold value, a switch for receiving a signal from said integrator and for producing a switch output signal, said switch being conditioned by a signal having a second threshold value such that said switch produces said output signal only if said integrator signal exceeds said second threshold value, said method comprising the steps of delivering a single test pulse signal to said integrator in place of said accelerometer signal, said single test pulse signal being delivered to said integrator over a given time period, and the amplitude of said single test pulse being greater than said first threshold value for at least a portion of said time period, said single test pulse exceeding said first threshold value at a predetermined first point in said time period, said single test pulse exceeding said first threshold value for at least a portion of said time period sufficient for said integrator to produce an integrator output signal having a magnitude greater than said second threshold value, and monitoring the output of said switch whereby proper operation of said circuit is confirmed if said switch produces a switch output signal at a predetermined second point in time directly related to said first point in said time period, and further independently checking said first threshold value by selecting a single test pulse of a predetermined first form and monitoring said integrator output signal, and independently checking said second threshold value by selecting a single test pulse of said predetermined first form and monitoring said switch output signal and said integrator output signal.

Claim 2

A method for testing a circuit for releasing an airbag comprising an accelerometer, an integrator for receiving a signal from the accelerometer, said integrator being conditioned by a signal having a first threshold value such that said integrator integrates a signal received from said accelerometer only if said accelerometer signal exceeds said first threshold value, a switch for receiving a signal from said integrator and for producing a switch output signal, said switch being conditioned by a signal having a second threshold value such that said switch produces said output signal only if said integrator signal exceeds said second threshold value, said method comprising the steps of delivering a single test pulse signal to said integrator in place of said accelerometer signal, said single test pulse signal being delivered to said integrator over a given time period, and the amplitude of said single test pulse being greater than said first threshold value for at least a portion of said time period, said single test pulse exceeding said first threshold value at a predetermined first point in said time period, said single test pulse exceeding said first threshold value for at least a portion of said time period sufficient for said integrator to produce an integrator output signal having a magnitude greater than said second threshold value, and monitoring the output of said switch whereby proper operation of said circuit is confirmed if said switch produces a switch output signal at a predetermined second point in time directly related to said first point in said time period, and further independently checking said first threshold value by selecting a single test pulse of a predetermined first form and monitoring said integrator output signal, and independently checking said second threshold value by selecting a single test pulse of said predetermined first form and monitoring said switch output signal and said integrator output signal.

Claim 6

The method of testing a circuit according to claims 3 or 4 wherein said test pulse exceeds said first threshold value at said predetermined first point in time and wherein said integrator output signal exceeds said second threshold value at a point in time that is determined from said first predetermined point in time.