Method for digitally controlling a sensor system

• US 7,010,983 B2
• Filed: 05/19/2004
• Issued: 03/14/2006
• Est. Priority Date: 05/31/2002
• Status: Expired due to Term

• Current Assignee: Brooks Instrument LLC (Illinois Tool Works Inc.)
• Original Assignee: Mykrolis Corporation (Entegris Incorporated)
• Inventors: Edwards, Marvin B., Arrant, Edwin K., Albert, David M.
• Primary Examiner(s): OEN, WILLIAM L
• Application Number:
  US10/848,739
• Publication Number:
  US 20050011271A1
• Time in Patent Office: 664 Days
• Field of Search: 73700-756, 34087004-87021
• US Class Current: 73/714
• 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 method for digitally controlling a sensor system comprising:

receiving an analog sensor signal;

converting the analog sensor signal to a digital sensor signal; and

processing the signal to provide an output signal indicating a measured parameter corresponding to the sensor signal; and

digitally controlling one or more components operable to modify the analog sensor signal prior to digitization.

2. The method of claim 1, wherein the method is implemented in a digital signal processor (DSP) and wherein the DSP is embedded in the sensor.

3. The method of claim 1, wherein the method is implemented in a microcontroller and wherein the microcontroller is embedded in the sensor.

4. The method of claim 1, further comprising producing the sensor signal using a digital capacitance gauge.

5. The method of claim 1, further comprising performing iterations of a control loop in a kernel module, wherein the control loop comprises execution of all of a set of high priority tasks and execution of one or more low priority tasks.

6. The method of claim 5, further comprising performing each iteration of the control loop at a periodic time.

7. The method of claim 5, wherein the high priority tasks comprise at least one or more of the group consisting of:

reading the digital sensor signal from the analog-to-digital converter;

calculating a linearized pressure value from the digital sensor signal;

writing the linearized pressure value to a digital-to-analog converter; and

conveying the linearized pressure value to one or more port buffers.

8. The method of claim 1, further comprising performing an automatic calibration procedure.

9. The method of claim 8, wherein performing the automatic calibration procedure comprises computing a set of calibration constants upon which linearization calculations are based.

10. The method of claim 8, wherein computing the set of calibration constants is performed using a regression procedure.

11. The method of claim 8, further comprising archiving the set of calibration constants in a non-volatile memory.

12. The method of claim 8, further comprising performing the automatic calibration procedure using calibration data imported from a calibration stand.

13. The method of claim 1, further comprising performing an automatic zero adjust procedure.

14. The method of claim 13, further comprising controlling an analog zero adjust module according to control data generated by the automatic zero adjust procedure.

15. The method of claim 13, further comprising locking out the automatic zero adjust procedure unless a predetermined set of conditions is met.

16. The method of claim 1, further comprising performing one or more embedded diagnostic procedures.

17. The method of claim 16, further comprising providing an indication of a fault condition detected by the one or more embedded diagnostic procedures.

18. The method of claim 16, further comprising archiving detected fault conditions.

19. The method of claim 1, further comprising transmitting diagnostic data resulting from the one or more embedded diagnostic procedures to a diagnostic port.

20. The method of claim 1, further comprising linearizing the digital sensor signal.

21. The method of claim 20, wherein the digital sensor signal is linearized using linearization expressions based on values stored in a non-volatile memory.

22. The method of claim 21, wherein the non-volatile memory is an EEPROM.

23. The method of claim 1, further comprising temperature compensating the digital sensor signal.

24. A method for digitally controlling a sensor system comprising:

receiving an analog sensor signal;

converting the analog sensor signal to a digital sensor signal;

processing the signal to provide an output signal indicating a measured parameter corresponding to the sensor signal;

performing iterations of a control loop in a kernel module, wherein the control loop comprises execution of all of a set of high priority tasks and execution of one or more low priority tasks;

wherein the low priority tasks comprise at least one or more of the group consisting of;

processing communication messages received from a diagnostics port;

processing control area network messages;

performing ambient temperature compensation;

performing a closed loop heater algorithm;

servicing temperature LEDs;

monitoring overpressure and zero adjust inputs;

servicing status LEDs and switches;

servicing an EEPROM;

performing and automatic analog scaling procedure;

performing an automatic zero adjust procedure; and

performing and embedded diagnostic procedure.

25. A method for digitally controlling a sensor system comprising:

receiving an analog sensor signal;

converting the analog sensor signal to a digital sensor signal;

processing the signal to provide an output signal indicating a measured parameter corresponding to the sensor signal;

performing an automatic zero adjust procedure;

controlling an analog zero adjust module according to control data generated by the automatic zero adjust procedure, wherein the zero adjust procedure is locked out unless a predetermined set of conditions is met; and

wherein the predetermined set of conditions include one or more of the group consisting of;

inlet pressure being below a zero adjust limit of the sensor;

the sensor being at a set point temperature;

ambient temperature of the electronics being within a predetermined range;

an overpressure signal not being asserted; and

no fault conditions existing within the sensor or controller.