Normalized process dynamics

• US 9,551,599 B2
• Filed: 09/23/2013
• Issued: 01/24/2017
• Est. Priority Date: 09/23/2013
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Miller, John Philip, Hedtke, Robert Carl
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): COTEY, PHILIP L
• Application Number:
  US14/033,884
• Publication Number:
  US 20150088279A1
• Time in Patent Office: 1,219 Days
• Field of Search: 700/55, 702/190, 374/141
• 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: G01K 7/00 Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat giving results other than momentary value of temperature G01K3/00 ; Power supply therefor, e.g. using thermoelectric elements
• CPC Class Codes: G05B 15/02 electric
• 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
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A sensing system includes a filter construction module that constructs a high pass filter for filtering sensor values indicative of a process variable, the filter construction module setting values for parameters of the filter based on a temperature value indicative of a temperature of the sensor that produced the sensor values.

Claims

1. A process field device comprising:

a process variable sensor providing a sensor signal indicative of a process variable;

a temperature sensor providing a temperature sensor signal indicative of a temperature of the process variable sensor;

converter circuitry for converting the sensor signal into sensor values and the temperature sensor signal into temperature values;

a processor implementing a digital filter that filters the sensor values to produce filtered sensor values and executing statistical process monitoring instructions that compute a statistical value from the filtered sensor values, wherein the digital filter is temperature-dependent such that the filter changes as the temperature values change.

2. The process field device of claim 1 wherein the processor constructs the digital filter by applying a temperature value to an equation determined by fitting a curve to parameter values determined for filters constructed for a plurality of temperature values.

3. The process field device of claim 2 wherein the filters constructed for a plurality of temperature values are each constructed to produce a target frequency response.

4. The process field device of claim 3 wherein the target frequency response comprises a frequency response of a standard deviation of filtered sensor values.

5. The process field device of claim 3 wherein the target frequency response comprises a frequency response associated with a model sensor operating in a different range from the sensor and at a selected temperature.

6. The process field device of claim 3 wherein the target frequency response comprises a frequency response of a model sensor with a constant frequency response at all temperatures.

7. A control system comprising:

a filter that filters a series of sensor values to produce filtered values; and

a statistical process monitoring unit that determines a statistical value from the filtered values and that issues an alert when the statistical value crosses a threshold, wherein the filter filters the sensor values to achieve a desired frequency response in the statistical value that matches a frequency response in the statistical value produced from sensor values generated by a sensor operating in a selected range.

8. The control system of claim 7 wherein the filter comprises a temperature-dependent filter that is constructed by applying the temperature value to respective equations that each define a separate parameter of the filter.

9. The control system of claim 8 wherein each equation is constructed by fitting a curve to values of a filter parameter determined at different temperatures.

10. The control system of claim 7 wherein the desired frequency response of the statistical value further matches a frequency response in the statistical value produced from sensor values generated by the sensor operating at a selected temperature.

11. The control system of claim 7 wherein the desired frequency response of the statistical value comprises a frequency response produced at least in part by a sensor operating in a different range from a sensor that produced the series of sensor values.

12. The control system of claim 7 wherein the desired frequency response of the statistical value comprises a frequency response produced at least in part by a sensor that was manufactured differently from a sensor that produced the series of sensor values.