Sensing apparatus having a sensing bridge circuit and a temperature detecting bridge circuit for detecting a physical quantity and a related temperature compensating method

• US 6,329,825 B1
• Filed: 11/16/1999
• Issued: 12/11/2001
• Est. Priority Date: 11/26/1998
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Tanaka, Hiroaki, Toyoda, Inao
• Primary Examiner(s): Nguyen, Vinh P.
• Assistant Examiner(s): PATEL, PARESH H
• Application Number:
  US09/440,886
• Time in Patent Office: 756 Days
• Field of Search: 324/600, 324/725, 324/705, 324/706, 324/710, 324/720, 324/721, 702/98, 374/143
• US Class Current: 324/725
• CPC Class Codes: G01D 3/0365 the undesired influence being measured using a separate sensor, which produces an influence related signal
• CPC Class Codes: G01L 9/065 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A pressure detecting bridge circuit produces a sensor signal Sd. A temperature detecting bridge circuit produces a temperature signal St. A reference voltage generating circuit produces a reference signal Sa. An analog multiplexer processes these signals Sd, St and Sa in a time-divisional manner. A differential amplification circuit and an A/D conversion circuit are commonly used to obtain the digital data corresponding to the sensor signal Sd, the temperature signal St and the reference signal Sa. The temperature detecting bridge circuit includes reference resistance elements. By adjusting the design resistance values of the reference resistance elements, the variation width of the sensor signal Sd in a pressure measuring range of the pressure detecting bridge circuit is substantially equalized in advance with the variation width of the temperature signal St in a temperature measuring range of the temperature detecting bridge circuit.

Claims

1. A sensing apparatus comprising:

a sensing bridge circuit including a plurality of resistance elements for generating a sensor signal having a voltage level responsive to a detected physical quantity;

a temperature detecting bridge circuit including at least one temperature-sensing resistance element having a predetermined temperature coefficient and at least one reference resistance element having a temperature coefficient equal to or nearly equal to 0 for generating a temperature signal having a voltage level responsive to a temperature of said sensing bridge circuit, said temperature detecting bridge circuit further including at least one trimming resistor to adjust a variation width of said temperature signal produced from the temperature detecting bridge circuit;

a signal selecting circuit for selectively outputting said sensor signal and said temperature signal; and

an amplification circuit for amplifying the signals successively outputted from said signal selecting circuit;

wherein a variation width of said sensor signal in a measuring range of the detected physical quantity of said sensing bridge circuit is substantially equalized in advance with the variation width of said temperature signal in a temperature measuring range of said temperature detecting bridge circuit by means of said at least one trimming resistor.

2. The sensing apparatus in accordance with claim 1, wherein

said sensing bridge circuit and said temperature detecting bridge circuit are formed on a same semiconductor substrate.

3. The sensing apparatus in accordance with claim 1, wherein the variation width of said sensor signal in the measuring range of the detected physical quantity of said sensing bridge circuit is substantially equalized with the variation width of said temperature signal in the temperature measuring range of said temperature detecting bridge circuit by adjusting a design resistance value of said at least one reference resistance element.

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

an A/D conversion circuit for converting the amplified signals of said amplification circuit into digital data corresponding to said sensor signal and said temperature signal; and

signal processing means for performing digital calculating processing based on the digital data produced from said A/D conversion circuit to calculate the detected physical quantity corresponding to said sensor signal and correct the detected physical quantity in accordance with said temperature signal.

5. The sensing apparatus in accordance with claim 4, wherein

said A/D conversion 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 amplified signals, 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. The sensing apparatus in accordance with claim 1, further comprising:

a reference voltage generating circuit for generating a reference signal having a constant voltage level irrespective of the detected physical quantity and the temperature of said sensing bridge circuit, said reference signal being selected by said signal selecting circuit and supplied to said amplification circuit;

an A/D conversion circuit for converting the amplified signals of said amplification circuit into digital data corresponding to said sensor signal, said temperature signal and said reference signal; and

signal processing means for performing digital calculating processing based on the digital data produced from said A/D conversion circuit to calculate the detected physical quantity corresponding to said sensor signal and correct the detected physical quantity in accordance with said temperature signal and said reference signal.

7. The sensing apparatus in accordance with claim 6, wherein

said A/D conversion 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 amplified signals, 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.

8. The sensing apparatus in accordance with claim 1, wherein a zero-crossing point of said sensor signal in the measuring range of detected physical quantity of said sensing bridge circuit is substantially equalized in advance with a zero-crossing point of said temperature signal in the temperature measuring range of said temperature detecting bridge circuit.

9. The sensing apparatus in accordance with claim 8, wherein said temperature detecting bridge circuit has at least one trimming resistor to adjust the zero-crossing point of said temperature signal produced from said temperature detecting bridge circuit.

10. The sensing apparatus in accordance with claim 1, wherein a power source for supplying electric power to said sensing apparatus is a battery.

11. The sensing apparatus in accordance with claim 1, wherein said at least one temperature-sensing resistance clement of said temperature detecting bridge circuit is a pair of temperature-sensitive resistors,

said at least one reference resistance element of said temperature detecting bridge circuit is a pair of temperature-insensitive resistors,

said pair of temperature-sensitive resistors and said pair of temperature-insensitive resistors are connected in a bridge pattern, and

said pair of temperature-insensitive resistors having an adjustable resistance value, wherein the adjustable resistance value is adjusted to adjust the variation width of the temperature signal.

12. The sensing apparatus in accordance with claim 11 wherein at least one trimming resistor is connected in series with said pair of temperature-sensitive resistors and said pair of temperature-insensitive resistors, and

said trimming resistor being configured to adjust a zero-crossing point of the temperature signal.

14. The method in accordance with claim 12, wherein the variation width of said sensor signal in the physical quantity measuring range of said sensing bridge circuit is substantially equalized with the variation width of said temperature signal in the temperature measuring range of said temperature detecting bridge circuit by adjusting a design resistance value of said at least one reference resistance element.

13. A method of adjusting temperature characteristics of a sensing apparatus,

said sensing apparatus comprising:

a sensing bridge circuit including a plurality of resistance elements for generating a sensor signal having a voltage level responsive to a detected physical quantity;

a temperature detecting bridge circuit including at least one temperature-sensing resistance element having a predetermined temperature coefficient and at least one reference resistance element having a temperature coefficient equal to or nearly equal to 0 for generating a temperature signal having a voltage level responsive to a temperature of said sensing bridge circuit, said temperature detecting bridge circuit further including at least one trimming resistor to adjust a variation width of said temperature signal produced from the temperature detecting bridge circuit; and

a signal selecting circuit for selectively outputting said sensor signal and said temperature signal;

said method comprising;

substantially equalizing a variation width of said sensor signal in a measuring range of the detected physical quantity of said sensing bridge circuit with a variation width of said temperature signal in a temperature measuring range of said temperature detecting bridge circuit by means of trimming at least one trimming resistor provided in said temperature detecting bridge circuit.

15. The method in accordance with claim 13, further comprising:

substantially equalizing a zero-crossing point of said sensor signal in the measuring range of the detected physical quantity of said sensing bridge circuit with a zero-crossing point of said temperature signal in the temperature measuring range of said temperature detecting bridge circuit.

16. The method in accordance with claim 15, wherein the zero-point of said temperature signal produced from said temperature detecting bridge circuit is controlled by trimming at least one trimming resistor provided in said temperature detecting bridge circuit.