Sensing apparatus including an A/D conversion circuit for detecting a physical quantity

• US 6,307,496 B1
• Filed: 10/04/1999
• Issued: 10/23/2001
• Est. Priority Date: 10/04/1999
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ikuta, Toshio, Endo, Noboru, Watanabe, Takamoto
• Primary Examiner(s): JeanPierre, Peguy
• Assistant Examiner(s): JeanGlaude, Jean Bruner
• Application Number:
  US09/411,319
• Time in Patent Office: 750 Days
• Field of Search: 341/155, 341/157, 341/166, 341/118, 341/119, 702/130
• US Class Current: 341/155
• CPC Class Codes: G01D 3/022 having an ideal characteristic, map or correction data stored in a digital memory
• CPC Class Codes: G01D 3/0365 the undesired influence being measured using a separate sensor, which produces an influence related signal
• CPC Class Codes: H03M 1/60 with intermediate conversion to frequency of pulses

Abstract

An analog multiplexer is provided to time divisionally process a reference signal Sa obtained from a reference voltage generating circuit, a temperature signal St obtained from a temperature detecting bridge circuit, and a sensor signal Sd obtained from a pressure detecting bridge circuit. These signals Sa, St and Sd are converted into digital data through a common differential amplification circuit and a common A/D conversion circuit. A correction circuit calculates an applied pressure value based on the digital data produced from the A/D conversion circuit, as a value corrected with reference to the temperature signal St and the reference signal Sa.

Claims

1. A sensing apparatus comprising:

a sensing circuit for generating a sensor signal having a voltage level responsive to a detected physical quantity;

a temperature detecting circuit for generating a temperature signal having a voltage level responsive to a temperature of said sensing circuit;

a reference voltage generating circuit for generating a reference signal having a constant voltage level irrespective of said detected physical quantity and the temperature of said sensing circuit;

an analog multiplexer which receives each of said sensor signal, said temperature signal, and said reference signal and which selectively, successively outputs said sensor signal, said temperature signal, and said reference signal;

amplification means which successively receives said sensor signal, said temperature signal, and said reference signal from said analog multiplexer and which amplifies said sensor signal, said temperature signal, and said reference signal to produce an amplified voltage signal;

an A/D conversion circuit which receives the amplified voltage signal as a power source voltage and which converts said amplified voltage signal into digital data as an A/D conversion value during a predetermined time; and

signal processing means for performing calculations based on said digital data in such a manner that the sensor signal corresponding to the detected physical quantity is corrected with respect to the temperature signal and with respect to said reference signal.

2. The sensing apparatus in accordance with claim 1, wherein said physical quantity to be detected by said sensing circuit is pressure.

3. The sensing apparatus in accordance with claim 1, further comprising:

a power source circuit which is operative to supply a constant voltage to said sensing circuit, said temperature detecting circuit, said reference voltage generating circuit, said analog multiplexer, and said amplification means, and

control means for stopping an operation of said power source circuit when said A/D converting circuit has completed the operation for converting said sensor signal, said temperature signal, and said reference signal into digital data.

4. The sensing apparatus in accordance with claim 1, further comprising a constant voltage power source for maintaining the amplified signal of said amplification means at a predetermined voltage level.

5. A sensing apparatus comprising:

a sensing circuit for generating a sensor signal having a voltage level responsive to a detected physical quantity;

a temperature detecting circuit for generating a temperature signal having a voltage level responsive to a temperature of said sensing circuit;

a reference voltage generating circuit for generating a reference signal having a constant voltage level irrespective of said detected physical quantity and the temperature of said sensing circuit;

an analog multiplexer which receives each of said sensor signal, said temperature signal, and said reference signal and which selectively, successively outputs said sensor signal, said temperature signal, and said sensing signal;

amplification means which successively receives said sensor signal, said temperature signal, and said reference signal from said analog multiplexer and which amplifies said sensor signal, said temperature signal, and said reference signal to produce an amplified voltage;

an A/D conversion circuit which receives the amplified voltage signal as a power source voltage and which converts said amplified voltage signal into digital data as an A/D conversion value during a predetermined time; and

signal processing means for performing calculations based on said digital data in such a manner that the sensor signal corresponding to the detected physical quantity is corrected with respect to the temperature signal and with respect to said reference signal;

wherein said A/D converting circuit includes a ring-gate delay circuit comprising a plurality of inverting circuits connected in a ring pattern and having an inverting operation time varying in accordance with said power source voltage, and

each of said sensor signal, said temperature signal, and said reference signal, when serving as said power source voltage of said ring-gate delay circuit, is converted into digital data based on a pulse signal circulation frequency when a pulse signal is entered into said ring-gate delay circuit.

6. A sensing apparatus comprising:

a sensing circuit for generating a sensor signal having a voltage level responsive to a detected physical quantity;

a temperature detecting circuit for generating a temperature signal having a voltage level responsive to a temperature of said sensing circuit;

a reference voltage generating circuit for generating a reference signal having a constant voltage level irrespective of said detected physical quantity and the temperature of said sensing circuit;

an analog multiplexer which receives each of said sensor signal, said temperature signal, and said reference signal and which selectively, successively outputs said sensor signal, said temperature signal, and said sensing signal;

amplification means which successively receives said sensor signal, said temperature signal, and said reference signal from said analog multiplexer and which amplifies said sensor signal, said temperature signal, and said reference signal to produce an amplified voltage;

an A/D conversion circuit which receives the amplified voltage signal as a power source voltage and which converts said amplified voltage signal into digital data as an A/D conversion value during a predetermined time; and

signal processing means for performing calculations based on said digital data in such a manner that the sensor signal corresponding to the detected physical quantity is corrected with respect to the temperature signal and with respect to said reference signal;

wherein said physical quantity to be detected by said sensing circuit is pressure;

wherein said signal processing means is for calculating a pressure P applied to said sensing circuit according to the following equation

7. A sensing apparatus comprising:

a sensing circuit for generating a sensor signal having a voltage level responsive to a detected physical quantity;

a temperature detecting circuit for generating a temperature signal having a voltage level responsive to a temperature of said sensing circuit;

a reference voltage generating circuit for generating a reference signal having a constant voltage level irrespective of said detected physical quantity and the temperature of said sensing circuit;

an A/D conversion circuit including a ring-gate delay circuit comprising a plurality of inverting circuits connected in a ring pattern and having an inverting operation time varying in accordance with said power source voltage, for converting each of said sensor signal, said temperature signal, and said reference signal, when serving as a power source voltage of said ring-gate delay circuit, into binary data based on a pulse signal circulation frequency when a pulse signal is entered into said ring-gate delay circuit;

signal processing means for performing calculations based on said digital data in such a manner that the physical quantity corresponding to said sensor signal is corrected with reference to the temperature signal and said reference signal; and

compensating means for compensating said power source voltage applied to said ring-gate delay circuit in said A/D conversion circuit, said compensating means including memory means for storing correction voltage data corresponding to offset amounts of said sensor signal, said temperature signal, and said reference signal under same conditions, wherein the power source voltage applied to said ring-gate delay circuit is corrected in accordance with said correction data when said sensor signal, said temperature signal, and said reference signal are selectively applied to said A/D conversion circuit as said power source voltage.

8. The sensing apparatus in accordance with claim 7, further comprising amplification means for amplifying said sensor signal, said temperature signal, and said reference signal and applies an amplified signal to said ring-gate delay circuit in said A/D conversion circuit.

9. The sensing apparatus in accordance with claim 8, wherein an amplification rate of said amplification means is determined in such a manner that said amplified signal of said amplification means contains a nonlinear error component equal to or less than 0.1%.

10. The sensing apparatus in accordance with claim 8, wherein an amplification rate of said amplification means is determined in such a manner that a difference between a maximum voltage level and a minimum voltage level of said amplified signal of said amplification means is equal to or less than 150 mV.

11. The sensing apparatus in accordance with claim 8, further comprising an analog multiplexer for selectively outputting said sensor signal, said temperature signal, and said reference signal, wherein

said amplification means is for amplifying an output signal selected by said analog multiplexer and applying the amplified signal as the power source voltage to said ring-gate delay circuit in said A/D conversion circuit.

12. The sensing apparatus in accordance with claim 7, wherein said A/D conversion circuit has a sampling period equal to or larger than 50 μ

sec.

13. The sensing apparatus in accordance with claim 7, wherein said memory means stores said correction voltage data in a quantized condition, and

said compensating means further comprises a selector for selectively outputting the correction voltage data from said memory means and a D/A conversion circuit for converting the selected correction voltage data into an analog voltage signal.

14. The sensing apparatus in accordance with claim 7, wherein said physical quantity to be detected by said sensing circuit is pressure.

15. The sensing apparatus in accordance with claim 14, wherein said sensing circuit includes a plurality of diffused resistance elements formed on a diaphragm of a semiconductor chip and arranged in a bridge connection pattern, and said temperature detecting circuit includes at least one temperature-sensitive diffused resistance element formed on said semiconductor chip.

16. The sensing apparatus in accordance with claim 14, wherein said signal processing means is for calculating a pressure P applied to said sensing circuit according to the following equation

17. A sensing apparatus comprising:

a pressure sensing circuit for generating a sensor signal having a voltage level responsive to a detected pressure;

a temperature detecting circuit for generating a temperature signal having a voltage level responsive to a temperature of said pressure sensing circuit;

a reference voltage generating circuit for generating a reference signal having a constant voltage level irrespective of said detected pressure and the temperature of said pressure sensing circuit;

an analog multiplexer for selectively outputting said sensor signal, said temperature signal, and said reference signal;

an A/D conversion circuit for converting said sensor signal, said temperature signal, and said reference signal into digital data; and

signal processing means for calculating a pressure P applied to said pressure sensing circuit according to the following equation

18. The sensing apparatus in accordance with claim 17, wherein

said analog multiplexer successively outputs said reference signal, said temperature signal, and said sensor signal in this order, and

said signal processing means is for successively performing first, second, and third calculation steps in this order, wherein said first calculation step is for performing the calculation based on said reference information A, said second calculation step is for performing the calculation based on said temperature information T and the calculation result of said first calculation step, and said third calculation step is for performing the calculation based on said pressure information D and the calculation result of said second calculation step.

19. The sensing apparatus in accordance with claim 17, wherein

said A/D converting circuit includes a ring-gate delay circuit comprising a plurality of inverting circuits connected in a ring pattern and having an inverting operation time varying in accordance with a power source voltage, and

each of said sensor signal, said temperature signal, and said reference signal, when serving as said power source voltage of said ring-gate delay circuit, is converted into digital data based on a pulse signal circulation frequency when a pulse signal is entered into said ring-gate delay circuit.