Method and apparatus for increasing the effective resolution of a sensor

• US 8,446,220 B2
• Filed: 05/09/2011
• Issued: 05/21/2013
• Est. Priority Date: 05/09/2011
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Rozgo, Paul, Jones, Ryan, Ricks, Lamar Floyd
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): NGUYEN, KHIEM D
• Application Number:
  US13/103,913
• Publication Number:
  US 20120286872A1
• Time in Patent Office: 743 Days
• Field of Search: 330/174, 324/251, 324/207.2, 324/511
• US Class Current: 330/174
• CPC Class Codes: G01D 18/004 Continuous recalibration
• CPC Class Codes: H03M 1/1295 Clamping, i.e. adjusting the DC level of the input signal to a predetermined value
• CPC Class Codes: H03M 1/183 the feedback signal controlling the gain of an amplifier or attenuator preceding the analogue/digital converter

Abstract

Methods and devices for increasing a sensor resolution are disclosed. In one example, a two measurement process is used. A first measurement is used to effectively measure across a full range (e.g. 0 to 5 VDC) of the sensor. This first measurement may identify the current operating point of the sensor (e.g. 3.5 VDC). A second measurement may then be made to effectively measure across a sub-range of the sensor that encompasses the current operating point of the sensor (e.g. across a sub-range of 3.0 to 4.0 VDC for a current operating point of 3.5 VDC). The gain of the amplifier may be raised during the second measurement to produce a higher resolution measurement. In some cases, the first measurement may be used to determine an appropriate offset that may be applied so as to scale the amplifier to the desired sub-range of sensor that includes the current operating point of the sensor. In some cases, the two measurements may be used together to compute an effectively higher resolution measurement signal. In some cases, this may allow for a smaller and/or cheaper sensor to be used, while still achieving good results.

Claims

1. Apparatus for processing an analog sensor output signal from a sensor, comprising:

an amplifier block, the amplifier block having two or more gain settings, the amplifier block receiving an analog sensor output signal from the sensor;

an offset block for selectively applying an offset to the analog sensor output signal when instructed to do so to output an offset analog sensor output signal; and

a controller coupled to the amplifying block and the offset block, the controller causing the amplifier block to amplify the analog sensor output signal using a first gain setting to produce a lower resolution analog sensor output signal over a first range, the controller using a measure related to the lower resolution analog sensor output signal to determine an offset value, the controller instructing the offset block to apply the determined offset value to the analog sensor output signal, resulting in the offset analog sensor output signal, the controller also causing the amplifier block to amplify the offset analog sensor output signal using a second gain setting that is higher than the first gain setting to produce a higher resolution analog sensor output signal over a second range, wherein the second range is a subset of the first range.

2. The apparatus of claim 1, further comprising:

an analog-to-digital converter;

a memory; and

wherein the analog-to-digital converter converts the lower resolution analog sensor output signal to a lower resolution digital sensor output signal, and the controller stores the lower resolution digital sensor output signal to the memory, the controller further using the lower resolution digital sensor output signal stored in the memory to determine the offset value.

3. The apparatus of claim 2, wherein the analog-to-digital converter converts the higher resolution analog sensor output signal into a higher resolution digital sensor output signal, and the controller stores the higher resolution digital sensor output signal to the memory.

4. The apparatus of claim 3, wherein the controller determines a composite digital sensor output signal using the lower resolution digital sensor output signal and the higher resolution digital sensor output signal, and outputs the composite digital sensor output signal.

5. The apparatus of claim 4, wherein the controller stores the composite digital sensor output signal to the memory.

6. The apparatus of claim 1, wherein the analog sensor output signal corresponds to an output of a Wheatstone bridge.

7. The apparatus of claim 1, wherein the analog sensor output signal corresponds to an output of a pressure sensor.

8. The apparatus of claim 1, wherein the analog sensor output signal corresponds to an output of a flow sensor.

9. The apparatus of claim 1, wherein the analog sensor output signal corresponds to an output of a magnetic proximity sensor.

10. The apparatus of claim 1, wherein the analog sensor output signal corresponds to an output of an accelerometer or gyro.

11. The apparatus of claim 1, further comprises a pre-amplifier that pre-amplifies the analog sensor output signal before the analog sensor output signal reaches the amplifier block.

12. The apparatus of claim 1, wherein the amplifier block includes a variable gain amplifier.

13. The apparatus of claim 1, wherein the amplifier block, the offset block and the controller are situated on a common integrated circuit.

14. A method for processing an analog sensor output signal comprising:

receiving an analog sensor output signal from a sensor;

amplifying the analog sensor output signal using a first gain to produce a lower resolution amplified analog sensor output signal;

using a measure related to the lower resolution amplified analog sensor output signal to determine an offset value;

applying the offset value to the analog sensor output signal, resulting in an offset analog sensor output signal; and

amplifying the offset analog sensor output signal using a second gain that is higher than the first gain to produce a higher resolution analog sensor output signal.

15. The method of claim 14, wherein the offset value is determined by:

converting the lower resolution amplified analog sensor output signal to a lower resolution digital sensor output signal;

storing the lower resolution digital sensor output signal to a memory;

using the lower resolution digital sensor output signal to determine the offset value.

16. The method of claim 15, further comprising:

converting the higher resolution analog sensor output signal to a higher resolution digital sensor output signal.

17. The method of claim 16, further comprising:

computing a composite digital sensor output signal using the lower resolution digital sensor output signal and the higher resolution digital sensor output signal.

18. A method for processing an analog sensor output signal, comprising:

receiving an analog sensor output signal;

amplifying the analog sensor output signal using a first gain to produce a lower resolution amplified analog sensor output signal;

converting the lower resolution amplified analog sensor output signal to a lower resolution digital sensor output signal;

storing the lower resolution digital sensor output signal to a memory;

using the lower resolution digital sensor output signal to determine an offset value;

applying the offset value to the analog sensor output signal, resulting in an offset analog sensor output signal;

amplifying the offset analog sensor output signal using a second gain that is higher than the first gain to produce a higher resolution amplified analog sensor output signal; and

converting the higher resolution amplified analog sensor output signal to a higher resolution digital sensor output signal.

19. The method of claim 18, further comprising storing the higher resolution digital sensor output signal to the memory.

20. The method of claim 18, further comprising:

computing a composite digital sensor output signal using the lower resolution digital sensor output signal and the higher resolution digital sensor output signal.