Extended durability sensing system
View Patent ↗The present invention provides a sensing system for monitoring an environment that includes at least two sensors and a control unit in communication with the sensors. At least one of the sensors is active providing an output signal to the control unit indicative of a sensed property, while the other sensor(s) is inactive and protected from the environment. During operation of the sensing system, if it is determined that the performance of the active sensor is abnormal, the inactive sensor is activated. Subsequently, the output signal of the abnormal sensor is ignored and the control unit utilizes an output signal of the previously inactive, but now active, sensor.
1. A sensing system for monitoring an environment comprising:
at least two sensors, at least one of the sensors being active and at least one of the sensors being inactive, the active sensor being exposed to said monitored environment and the inactive sensor being unexposed to the monitored environment; and
a control unit in communication with the sensors for activating at least one of the inactive sensors by exposing it to the environment when the active sensor is deemed abnormal.
2. The sensing system of claim 1 , wherein at least a portion of the inactive sensor is covered by a protective sheath.
3. The sensing system of claim 2 , wherein the protective sheath is a ceramic matrix having a fusible fiber reinforcement.
4. The sensing system of claim 2 , wherein the inactive sensor is activated by removing the protective sheath.
5. The sensing system of claim 1 , wherein the inactive sensor is activated by actuating the inactive sensor from an inactive position unexposed to the monitored environment to an active position exposed to the monitored environment.
6. The sensing system of claim 5 , wherein the inactive sensor is actuated to the active position by a resilient biasing member.
7. The sensing system of claim 1 , further including a switching device for switching between the use of the active sensor to one or more of the inactive sensors when the control unit has determined that the active sensor is abnormal.
8. The sensing system of claim 7 , wherein the switching device has multiplexing capability.
9. The sensing system of claim 1 , wherein the active sensor is deemed abnormal after a predetermined period of time.
10. The sensing system of claim 1 , wherein the active sensor supplies an output signal to the control unit.
11. The sensing system of claim 10 , wherein the active sensor is deemed abnormal when the output signal falls outside a predetermined range of acceptable output signals.
12. A sensing system for monitoring an exhaust-gas stream of an internal combustion engine, comprising:
at least two sensors disposed in the exhaust-gas stream, at least one of the sensors being active and exposed to the exhaust-gas stream and at least one of sensors being inactive and unexposed to the exhaust-gas stream; and
a control unit in communication with the sensors for activating at least one of the inactive sensors by exposing it to the environment when the active sensor is deemed abnormal.
13. The sensing system of claim 12 , wherein the sensors comprise at least one of an exhaust-gas species concentration sensor, an exhaust-gas temperature sensor and an exhaust-gas pressure sensor.
14. The sensing system of claim 12 , wherein at least a portion of the inactive sensor is covered by a protective sheath.
15. The sensing system of claim 14 , wherein the protective sheath is a ceramic matrix having a fusible fiber reinforcement.
16. The sensing system of claim 14 , wherein the inactive sensor is activated by removing the protective sheath.
17. The sensing system of claim 12 , wherein the inactive sensor is activated by actuating the inactive sensor from an inactive position unexposed to the monitored environment to an active position exposed to the monitored environment.
18. The sensing system of claim 17 , wherein the inactive sensor is actuated to the active position by a resilient biasing member.
19. The sensing system of claim 12 , further including a switching device for switching between the use of the active sensor to one or more of the inactive sensors when it is determined that the active sensor is abnormal.
20. The sensing system of claim 12 , wherein the active sensor is deemed abnormal after a predetermined period of time.
21. The sensing system of claim 12 , wherein the active sensor supplies an output signal to the control unit.
22. The sensing system of claim 21 , wherein the active sensor is deemed abnormal when the output signal falls outside a predetermined range of acceptable output signals.
23. A method of maintaining the performance of a sensing system for monitoring an environment, comprising the steps of:
providing at least two sensors in the sensing system, at least one of the sensors being active and at least one of the sensors being inactive, the active sensor being exposed to and actively monitoring the environment and the inactive sensor being unexposed to and not actively monitoring the environment;
determining when at least one of the active sensors is abnormal; and
exposing at least one of the inactive sensors to the monitored environment upon a determination that at least one of the active sensors is abnormal.
24. The sensing system of claim 23 , wherein at least a portion of the inactive sensors is covered by a protective sheath.
25. The sensing system of claim 24 , wherein the protective sheath is a ceramic matrix having a fusible fiber reinforcement.
26. The sensing system of claim 25 , wherein the step of exposing at least one of the inactive sensors to the monitored environment comprises removing the protective sheath.
27. The sensing system of claim 23 , wherein the step of exposing at least one of the inactive sensors to the monitored environment comprises actuating the inactive sensor from an inactive position unexposed to the monitored environment to an active position exposed to the monitored environment.
28. The method of claim 23 , further including the step of switching between the use of at least one of the active sensors to at least one of the inactive sensors when it is determined that at least one of the active sensors is abnormal.