Apparatus for measuring the degradation of a sensor time constant

Circuitry for monitoring the changes in the response time of a sensor while said sensor monitors fluctuations in a selected parameter comprising:

• a sensor having a selected response time and for producing a sensor signal indicative of fluctuations of a selected parameter;
• means for receiving said sensor signal indicative of fluctuations of said selected parameter and for indicating when the value of said sensor signal crosses a selected signal level;
• means for determining the number of times said sensor signal crosses said selected level in a selected time period to obtain a crossing rate;
• and
• means for comparing said crossing rate with a nominal crossing rate to determine a change in said selected response time of said monitored sensor.

Circuitry for online monitoring of the degradation of the response time of a sensor while said sensor monitors fluctuations of a selected parameter of the system comprising:

• a sensor having a selected response time and for producing a sensor signal indicative of fluctuations of a selected parameter;
• a Zero-Crossing Detector for receiving said sensor signal indicative of fluctuations of said selected parameter and for providing a first signal each time said sensor signal passes through the average value of said sensor signal;
• a counter to receive said first signals, to accumulate the number of said first signals received, and to provide a second signal when said accumulated number reaches a preselected value;
• a timer for providing a third signal after a preselected period of time has elapsed;
• and
• a control switch connected to said counter and said timer, and control switch for providing a fourth signal, which fourth signal is indicative of excessive degradation of said selected response time of said sensor, when said third signal is provided to said control switch before said second signal.