US 6,598,484 B2 · Physical quantity detection device

Abstract

Respective first ends of first and second strain gates are connected to a first voltage potential. First and second constant currents from first and second current sources flow through the first and second strain gages, respectively. The respective first ends of the first and second current sources are connected to second ends of the first and second strain gages, respectively. A voltage difference signal between the second ends of the first and second strain gages indicates the detected physical quantity. The first and second constant currents are adjusted to reduce the offset voltage in the voltage difference signal when no strain, that is, no physical quantity is measured. The first and second current sources may have substantially the same temperature coefficients in said first and second constant currents, respectively.

Claims19

Dependent claims

A physical quantity detection device comprising:

a first sensing resistor having a first resistance varying in accordance with a first physical quantity relating to a detection physical quantity;
a second sensing resistor having a second resistance varying in accordance with a second physical quantity relating to said detection physical quantity, respective first ends of said first and second sensing resistors being connected to a first voltage potential;
a first current source for flowing a first constant current through said first sensing resistor, a first end of said first current source being connected to a second end of said first sensing resistor;
a second current source for flowing a second constant current through said second sensing resistor, a first end of said second current source being connected to a second end of said second sensing resistor, second ends of said first and second current sources being connected to a second potential which is different from said first voltage potential;
and
outputting means for outputting a voltage difference signal indicative of said detection physical quantity between the second ends of said first and second sensing resistors.

3 more elements

A physical quantity detection device comprising:

a first circuit including a first sensing resistor and a first constant current source connected to said first sensing resistor in series through a first junction point, said first sensing resistor having a first resistance varying in accordance with a first physical quantity relating to a detection physical quantity, said first constant current source flowing a first constant current through said first sensing resistor;
a second circuit including a second sensing resistor and a second constant current source connected to said second sensing resistor in series through a second junction point, said second sensing resistor having a second resistance varying in accordance with a second physical quantity relating to said detection physical quantity, said second constant current source flowing a second constant current through said second sensing resistor, respective first ends of said first and second circuits being connected to a first potential, respective second ends of said first and second circuits being connected to a second potential which is different from said first potential;
and
outputting means for outputting a voltage difference signal indicative of said detection physical quantity between said first and second junction points.

1 more element

A method of adjusting an offset voltage in a physical quantity detection device comprising:

a first sensing resistor having a first resistance varying in accordance with a first physical quantity relating to a detection physical quantity;
a second sensing resistor having a second resistance varying in accordance with a second physical quantity relating to said detection physical quantity, respective first ends of said first and second sensing resistors being connected to a first voltage potential;
a first current source for flowing a first constant current through said first sensing resistor, a first end of said first current source being connected to a second end of said first sensing resistor, said first current source including a first control element and a first control resistor for flowing said first constant current on the basis of a first control voltage, and a first operational amplifier for generating said first control voltage on the basis of a first reference voltage;
a second current source for flowing a second constant current through said second sensing resistor, a first end of said second current source being connected to a second end of said second sensing resistor, said second current source including a second control element and a second control resistor for flowing said second constant current on the basis of a second control voltage, and a second operational amplifier for generating said second control voltage on the basis of a second reference voltage, wherein a difference voltage between a first junction point between said first sensing resistor and said first current source and a second junction point between said second sensing resistor and said second current source indicates said detection physical quantity, wherein said difference voltage includes an offset voltage, and said difference voltage is equal to the offset voltage when said detection physical quantity is not detected by said physical quantity device, said method comprising the steps of:
measuring said offset voltage;
and
controlling said first and second reference voltages to adjust said offset voltage on the basis of the result of the measuring.

4 more elements

Dependencies are inferred from the claim text.

Physical quantity detection device

Life of this patent

Physical quantity detection device

Life of this patent

Abstract

Claims19