Digitally controlled sensor system

• US 7,720,628 B2
• Filed: 12/29/2005
• Issued: 05/18/2010
• Est. Priority Date: 05/31/2002
• Status: Expired due to Term

• Current Assignee: Brooks Instrument LLC (Illinois Tool Works Inc.)
• Original Assignee: Brooks Instrument LLC (Illinois Tool Works Inc.)
• Inventors: Edwards, Marvin B., Arrant, Edwin K., Albert, David M.
• Primary Examiner(s): Nghiem; Michael P.
• Assistant Examiner(s): Le; Toan M
• Application Number:
  US11/321,238
• Publication Number:
  US 20060107746A1
• Time in Patent Office: 1,601 Days
• Field of Search: 702/138, 702/50, 702 98- 99, 702188-189, 702/57, 702 64- 65, 702/140, 702/33, 702 52- 53, 702 85- 87, 702104-105, 702/127, 702130-132, 73700-702, 73714-716, 73718-720, 73724-726, 73/15.7, 73/15.9, 73/16.2, 73/18.8, 737/08, 340/870.21, 361/283.1, 361/283.4, 700/67, 700 75- 76, 700299-301, 700 9- 10
• US Class Current: 702/138
• CPC Class Codes: G01D 18/008 with calibration coefficients stored in memory
• CPC Class Codes: G01D 3/022 having an ideal characteristic, map or correction data stored in a digital memory
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 27/002 Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

Systems and methods for digitally controlling sensors. In one embodiment, a digital controller for a capacitance diaphragm gauge is embedded in a digital signal processor (DSP). The controller receives digitized input from a sensor AFE via a variable gain module, a zero offset module and an analog-to-digital converter. The controller automatically calibrates the received input by adjusting the variable gain and zero offset modules. The controller also monitors and adjusts a heater assembly to maintain an appropriate temperature at the sensor. The controller utilizes a kernel module that allocates processing resources to the various tasks of a gauge controller module. The kernel module repetitively executes iterations of a loop, wherein in each iteration, all of a set of high priority tasks are performed and one of a set of lower priority tasks are performed. The controller module thereby provides sensor measurement output at precisely periodic intervals, while performing ancillary functions as well.

Claims

1. A digital pressure sending system, comprising:

a sensor for measuring a pressure-related variable;

an analog front end (AFE), electrically coupled to the sensor, to convert the measured pressure-related variable into an analog signal;

a processing stage, electrically coupled to the AFE, to receive the analog signal and process the analog signal;

an analog to digital converter, electrically coupled to the processing stage, to convert the processed analog signal into a digital signal; and

a digital controller to receive the digital signal and to provide a digital control signal to control the processing stage; and

a digitally controlled sensor heating assembly to control a temperature of the sensor based upon a second digital control signal.

2. The system of claim 1, wherein the processing stage further comprises:

a zero offset stage, wherein the zero offset stage is operable to compensate for a zero offset drift.

3. The system of claim 2, wherein the sensor is a strain gauge or a capacitance manometer.

4. The system of claim 2, wherein the sensor measures capacitance and the AFE converts the capacitance measurement to an analog voltage signal.

5. The system of claim 2, wherein a variable gain stage and the zero offset stages are separated from the analog to digital converter.

6. The system of claim 2, wherein the digital controller includes a digital processing stage to process the digital signal.

7. The system of claim 6, wherein the processing performed by the digital processing stage comprises linearization.

8. The system of claim 2, wherein the digital control signal is provided to the zero offset stage in response to a manually input zero adjust command.

9. The system of claim 2, further comprising an ambient temperature sensor for measuring an ambient temperature, wherein the digital controller compensates the digital signal for the ambient temperature.

10. The system of claim 2, wherein the digital controller is a DSP or a micro controller.

11. The system of claim 2, wherein the digital controller digitally processes the digital signal and provides the digitally processed digital signal to a controller area network of a DeviceNet communications link.

12. A method of measuring pressure, comprising:

measuring a pressure-related variable indicative of a measured pressure using a sensor;

converting the pressure-related variable to an analog pressure signal;

processing the analog pressure signal;

converting the processed analog signal into a digital signal; and

providing an output signal indicative of the measured pressure based upon the digitally processed digital signal;

wherein the processing of the analog pressure signal is based upon a first digital control signal, and wherein the method further comprises controlling a temperature of the sensor based upon a second digital control signal.

13. The method of claim 12, wherein the processing of the analog pressure signal comprises amplifying the analog pressure signal or compensating for a zero offset drift based upon the first digital control signal.

14. The method of claim 12, wherein the output signal is provided to a controller area network of a DeviceNet communications link.

15. The method of claim 12, wherein the sensor is a strain gauge or a capacitance manometer.

16. A method of measuring pressure, comprising:

receiving an analog pressure signal indicative of a measured pressure;

processing the analog pressure signal;

converting the processed analog signal into a digital signal;

providing an output signal indicative of the measured pressure based upon the digitally processed digital signal; and

providing a digital control signal in response to a manually input zero adjust command;

wherein the processing of the analog pressure signal comprises compensating for a zero offset drift based upon the digital control signal.

17. The method of claim 16, wherein the output signal is provided to a controller area network or a DeviceNet communications link.

18. A method of measuring pressure, comprising:

receiving an analog pressure signal indicative of a measured pressure;

processing the analog pressure signal;

converting the processed analog signal into a digital signal; and

providing an output signal indicative of the measured pressure based upon the digitally processed digital signal;

wherein the processing of the analog pressure signal is based upon a digital control signal;

wherein the digital control signal includes a first digital control signal and a second digital control signal, and wherein the processing of the analog pressure signal comprises amplifying the analog pressure signal based upon the first digital control signal and compensating for a zero offset drift based upon the second digital control signal.

19. The method of claim 18, further comprising linearizing the digital signal.

20. The method of claim 18, wherein the output signal is provided to a controller area network for a DeviceNet communications link.

21. A pressure sensor system, comprising:

a sensor for measuring a pressure-related variable;

an analog front end (AFE), electrically coupled to the sensor, to convert the measured pressure-related variable into an analog signal;

a processing stage, electrically coupled to the APE, to receive the analog signal and process the analog signal;

an analog to digital converter, electrically coupled to the processing stage, to convert the processed analog signal into a digital signal; and

a digital controller to receive the digital signal and to provide to the processing stage a digital control signal based upon the received digital signal;

wherein the processing stage processes the analog signal to automatically adjust a signal zero offset and variable gain based upon the digital control signal while the pressure sensor system is in operation.