Method for digitally controlling a sensor system
View Patent ↗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.
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.