Method for continuous sensor self-test
A method and device for self-test of a sensor. The method includes stimulating the sensor with signals that generate sensor outputs at a frequency that differs from the frequency of expected sensed parameter signals. The sensor output is filtered to remove the effects of the stimulation inputs, generating a sensed parameter signal. The unfiltered sensor output is compared to the expected output of the sensor with the stimulus input. A malfunctioning sensor may be detected by the comparison and appropriate action may then be taken.
1. A method for determining a sensed parameter using a sensor, the sensor generating a signal, the sensor including complementary self-test stimulation inputs, the method comprising:
a. stimulating the sensor using the complementary self-test stimulation inputs;
b. filtering the sensor signal;
c. determining the sensed parameter based on the filtered sensor signal;
d. comparing the sensor signal to an expected signal and generating a sensor self-test signal based at least in part on the comparison; and
e. periodically repeating steps a through d.
2. A method according to claim 1 , wherein the sensor stimulation is characterized by a stimulation frequency and the stimulation frequency and the signal frequency of the sensed parameter differ substantially.
3. A method according to claim 1 wherein the sensor stimulation is characterized by a stimulation on-period and a stimulation off-period and the sensed parameter value is determined substantially during the sensor stimulation off-period.
4. A method according to claim 3 , further including comparing the sensor signal to an expected sensor signal during the sensor stimulation on-period and generating a sensor self-test signal based at least in part on the comparison.
5. A method according to claim 1 wherein the sensed parameter is at least one of an acceleration and a rotation.
6. A sensor assembly for determining a sensed parameter while testing a sensor, the sensor assembly comprising:
a. the sensor, the sensor including an output for generating an output signal, the sensor including complementary self-test stimulation inputs;
b. a stimulator connected to the sensor for injecting a stimulation signal;
c. a filter connected to the sensor output, such that the filter substantially removes the portion of the output signal due to the stimulation signal; and
d. a comparator connected to the sensor output, the comparator generating a sensor self-test signal.
7. A sensor assembly according to claim 6 , wherein the stimulation signal is characterized by a stimulation frequency and the stimulation frequency and the signal frequency of the sensed parameter differ substantially.
8. A sensor assembly according to claim 6 wherein the sensed parameter is at least one of an acceleration and a rotation.
9. A sensor assembly according to claim 6 wherein the assembly includes a self-test output signal.
10. A computer program product for use on a computer system for determining a sensed parameter value while performing sensor self-test, the system including a sensor, the sensor including complementary self-test stimulation inputs, the computer program product comprising a computer usable medium having computer readable program code thereon, the computer readable program code including program code for:
a. stimulating the sensor using the complementary self-test stimulation inputs;
b. filtering a sensor output signal;
c. determining the sensed parameter value based on the filtered sensor signal; and
d. comparing the sensor signal to an expected signal and generating a sensor self-test signal based at least in part on the comparison.
11. A computer program product according to claim 10 further including program code for:
e. periodically repeating steps a through d.
12. A computer program product according to claim 10 wherein the sensor includes complementary self-test inputs.
13. A computer program product according to claim 10 wherein the sensed parameter is at least one of an acceleration and a rotation.