Degrading sensor detection implemented within a transmitter

• US 9,207,670 B2
• Filed: 09/19/2011
• Issued: 12/08/2015
• Est. Priority Date: 03/21/2011
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Rud, Jason H.
• Primary Examiner(s): Henson, Mischita
• Application Number:
  US13/236,002
• Publication Number:
  US 20120245895A1
• Time in Patent Office: 1,541 Days
• Field of Search: 702/15, 702/116, 702/127, 702/183
• US Class Current: 1/1
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G05B 23/0221 Preprocessing measurements, e.g. data collection rate adjustment; Standardization of measurements; Time series or signal analysis, e.g. frequency analysis or wavelets; Trustworthiness of measurements; Indexes therefor; Measurements using easily measured parameters to estimate parameters difficult to measure; Virtual sensor creation; De-noising; Sensor fusion; Unconventional preprocessing inherently present in specific fault detection methods like PCA-based methods

Abstract

A process variable transmitter includes a memory that stores a filtered sensor value that is calculated based on a prior received sensor value and a filtered rate of change value that is calculated based on a prior rate of change value. The process variable transmitter also includes a controller that receives a sensor value and compares it to the filtered sensor value to obtain a rate of change value. The controller also compares the rate of change value to the filtered rate of change value to obtain a deviation value, and generates an output indication, such as a sensor failure warning output, based on the deviation value. This is done within the process variable transmitter.

Claims

1. A process variable transmitter, comprising:

a sensor sensing a process variable and providing a sensor value indicative of the sensed process variable;

a memory storing a filtered sensor value that is calculated based on an average of a number of previously received sensor values, and a filtered rate of change value that is an average of a number of previously calculated rate of change values, the filtered rate of change values indicating rate of change of previously received sensor values; and

a controller receiving the sensor value from the sensor that senses the process variable, and comparing the sensor value to the filtered sensor value to obtain an estimate of the rate of change value, the controller further comparing the estimate of the rate of change value to the filtered rate of change value to obtain a deviation value, and identifying a sensor characteristic indicative of whether the sensor is operating correctly based on the deviation value.

2. The process variable transmitter of claim 1 and further comprising:

an output component providing an output indication of a sensor failure or degradation warning output to a host system over a communication link.

3. The process variable transmitter of claim 2 wherein the output component provides the sensor failure warning output over a process control loop.

4. The process variable transmitter of claim 2 wherein circuitry of the process variable transmitter is powered with power received from the process control loop.

5. The process variable transmitter of claim 1 wherein the controller calculates the filtered sensor value by generating a rolling average of previously received sensor values.

6. The process variable transmitter of claim 5 wherein the controller generates an updated filtered sensor value based on the sensor value and the filtered sensor value, and stores the updated filtered sensor value as the filtered sensor value in the memory.

7. The process variable transmitter of claim 6 wherein the controller calculates the filtered rate of change value by generating a rolling average of previously calculated rate of change values.

8. The process variable transmitter of claim 7 wherein the controller generates an updated filtered rate of change value based on the rate of change value and the filtered rate of change value and stores the updated filtered rate of change value as the filtered rate of change value in the memory.

9. The process variable transmitter of claim 1 wherein the controller receives a plurality of different sensor values from a plurality of different sensors and obtains a rate of change value corresponding to each of the plurality of sensor values.

10. The process variable transmitter of claim 9 wherein the controller compares characteristics of each of the plurality of sensor values with one another to determine whether the characteristics exhibit an expected relationship to one another.

11. The process variable transmitter of claim 1 wherein the controller compares the sensor value to the filtered sensor value according to an equation:

x=y−

y_i where

x is an estimate of the rate of change value;

y is the received sensor value

y_i is the average of a number I of prior received sensor values; and

wherein the controller obtains the deviation value according to an equation;

dev=|x−

x_i|

where x_i is an average of the number i of previous rate of change values.

12. A method of identifying characteristics of sensor signals, using a processor in a process variable transmitter, the method comprising:

receiving, at the processor in the process variable transmitter, a sensor value from a sensor that senses a process variable;

comparing, with the processor in the process variable transmitter, the sensor value to a stored sensor value stored in memory in the process variable transmitter, the stored sensor value comprising a rolling average of a plurality of previously received sensor values to determine an estimated rate of change;

determining a deviation value by comparing the determined estimated rate of change and an average of previous rate of change values, the previous rate of change values indicating rate of change of received sensor values;

identifying, with the processor in the process variable transmitter, a sensor characteristic based on the deviation value, indicative of whether the sensor is operating correctly; and

when the sensor is not operating correctly, generating, with the processor in the process variable transmitter, an output indication.

13. The method of claim 12 wherein the comparison generates a rate of change value, and further comprising:

comparing, with the processor in the process variable transmitter, the estimated rate of change value to a stored rate of change value stored in memory in the process variable transmitter, the stored rate of change value being indicative of the average of previous rate of change values; and

wherein identifying comprises identifying, with the processor in the process variable transmitter, the sensor characteristic based on the comparison of the rate of change value to the stored rate of change value.

14. The method of claim 13 wherein the stored rate of change value comprises a first, increasing rate of change value and a second, decreasing rate of change value and wherein comparing the rate of change value to the stored rate of change value comprises:

comparing the rate of change value to both the first and second rate of change values.

15. The method of claim 13 wherein comparing the rate of change value to the stored rate of change value provides a deviation value and wherein identifying the sensor characteristic comprises comparing the deviation value to a stored threshold value.

16. The method of claim 12 wherein receiving comprises:

receiving a sensor value corresponding to each of a plurality of different sensors; and

comparing the sensor values corresponding to the plurality of different sensors, and wherein identifying comprises identifying the sensor characteristic as being indicative of whether the sensor values exhibit an expected relationship relative to one another.

17. The method of claim 16 wherein generating the output indication comprises generating a sensor warning output when the sensor values from the plurality of different sensors fail to exhibit the expected relationship.

18. The method of claim 17 and further comprising:

transmitting the output indication as a sensor warning output to a host system over a process control loop.

19. The method of claim 12 and further comprising:

transmitting the output indication as a sensor warning output to a host system over a wireless communication link.

20. A process variable transmitter, comprising:

a memory storing a predefined sensor relationship indicative of an expected relationship between a rate of change in values from a first sensor and a rate of change in values from at least one second sensor; and

a processor disposed within the process control transmitter, and receiving input sensor values from the first and second sensors, the processor accessing the predefined sensor relationship in the memory to determine whether the input sensor values from the first and at least one second sensor exhibit the expected relationship, and, if not, the controller generating a sensor warning output identifying a sensor characteristic indicative of whether at least one of the first and second sensors are operating correctly.

21. The process variable transmitter of claim 20 wherein the first and at least one second sensors are all disposed to sense one or more process variables on the same process, and wherein the controller receives at least one of the input sensor values from a second process variable transmitter.