Automatic decision for self-diagnosis triggering in safety relevant sensors

A sensor module, comprising:

• a sensor configured to periodically measure a physical quantity and generate a sensor signal having plurality of sensor values, wherein each sensor value, of the plurality of sensor values, corresponds to a different measurement taken at a different sampling time;
• a signal processing chain comprising at least one signal processing component for conditioning the sensor signal to generate a plurality of conditioned sensor values corresponding to the plurality of sensor values, respectively;
• a memory configured to store each of the plurality of conditioned sensor values;
• and
• a processing circuit coupled to the sensor via the signal processing chain for receiving a current conditioned sensor value corresponding to a current measurement and coupled to the memory for receiving a previous conditioned sensor value corresponding to a previous measurement,
• wherein the processing circuit is configured monitor for a fault, including calculating a delta sensor value being an absolute value of a difference between the current conditioned sensor value and the previous conditioned sensor value, comparing the delta sensor value to a sensor threshold value, and triggering a diagnostic of the signal processing chain if the delta sensor value is greater than the sensor threshold value,
• wherein the processing circuit includes a controller that is configured to enter a diagnostic mode in response to the delta sensor value being greater than the sensor threshold value, and
• wherein in the diagnostic mode, the controller is configured to reconfigure the signal processing chain by disconnecting the sensor from an external stimulus such that the sensor generates a diagnostic signal independent from the physical quantity.

A method of performing a self-diagnostic in a sensor module, the method comprising:

• generating, by a sensor, a sensor signal having plurality of sensor values by periodically measuring a physical quantity, wherein each sensor value, of the plurality of sensor values, corresponds to a different measurement taken at a different sampling time;
• conditioning, by a signal processing chain, the sensor signal to generate a plurality of conditioned sensor values corresponding to the plurality of sensor values, respectively;
• storing each of the plurality of conditioned sensor values in a memory;
• receiving, by a processing circuit, a current conditioned sensor value from the signal processing chain and a previous conditioned sensor value from the memory, wherein the current conditioned sensor value corresponds to a current measurement and the previous conditioned sensor value corresponds to a previous measurement;
• monitoring, by the processing circuit, for a fault, including calculating a delta sensor value being an absolute value of a difference between the current conditioned sensor value and the previous conditioned sensor value, comparing the delta sensor value to a sensor threshold value, and triggering a diagnostic of the signal processing chain if the delta sensor value is greater than the sensor threshold value;
• entering, by a controller, a diagnostic mode in response to the delta sensor value being greater than the sensor threshold value;
• and
• while in the diagnostic mode, reconfiguring, by the controller, the signal processing chain by disconnecting the sensor from an external stimulus such that the sensor generates a diagnostic signal independent from the physical quantity.