Electrical technique for correcting bridge type mass air flow rate sensor errors resulting from ambient temperature variations
First Claim
1. A bridge type mass air flow rate sensor for generating an output signal related to mass air flow rate, comprisinga bridge circuit having legs;
- the bridge circuit having a mass air flow rate sensing first element in a leg;
the first element comprising a first resistor, the resistance of which changes as the temperature of the element changes;
the first element responding to changes in air flow rate by changing temperature;
the bridge circuit being balanced when the first element is at a particular temperature;
the resistance of the first resistor balancing the bridge when the first element is at the Particular temperature;
an ambient air temperature sensing second element in a leg of the bridge circuit for determining the resistance of the first resistor which will balance the bridge circuit;
the second element including means for responding to changes in ambient air temperature and changing the resistance of the first element at which the bridge circuit is balanced, thus changing the particular temperature;
means for supplying operating voltage to the bridge circuit including means responsive to bridge circuit imbalances caused by changes in the resistance of the first element for changing the power supplied to the first element to maintain the first element at the particular temperature;
means for sensing the current provided to the first element and producing an output signal related to mass air flow rate sensed by the first element;
means for sensing changes in the resistance of the first element at which the bridge is balanced and producing a correction factor; and
means for applying the correction factor to the output signal.
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Accused Products
Abstract
A mass flow rate sensor for providing an output signal related to mass flow rate past the sensor includes a bridge circuit for generating a first mass flow rate-related signal containing temperature-related errors and mass flow rate-related errors, a resistance for generating a second signal providing temperature error correction, and a resistance for generating a third signal providing mass flow rate error correction. Electrical circuitry operatively couples the bridge circuit and resistances together to provide the output signal. A method for providing an output signal related to mass flow rate includes the steps of generating a first mass flow rate-related signal containing temperature-related errors and mass flow rate-related errors, generating a second signal providing temperature error correction, generating a third signal providing mass flow rate error correction, and combining the first, second and third signals together to provide the output signal.
109 Citations
24 Claims
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1. A bridge type mass air flow rate sensor for generating an output signal related to mass air flow rate, comprising
a bridge circuit having legs; -
the bridge circuit having a mass air flow rate sensing first element in a leg; the first element comprising a first resistor, the resistance of which changes as the temperature of the element changes; the first element responding to changes in air flow rate by changing temperature; the bridge circuit being balanced when the first element is at a particular temperature; the resistance of the first resistor balancing the bridge when the first element is at the Particular temperature; an ambient air temperature sensing second element in a leg of the bridge circuit for determining the resistance of the first resistor which will balance the bridge circuit; the second element including means for responding to changes in ambient air temperature and changing the resistance of the first element at which the bridge circuit is balanced, thus changing the particular temperature; means for supplying operating voltage to the bridge circuit including means responsive to bridge circuit imbalances caused by changes in the resistance of the first element for changing the power supplied to the first element to maintain the first element at the particular temperature; means for sensing the current provided to the first element and producing an output signal related to mass air flow rate sensed by the first element; means for sensing changes in the resistance of the first element at which the bridge is balanced and producing a correction factor; and means for applying the correction factor to the output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A bridge type mass air flow rate sensor for generating an output signal related to mass air flow rate, comprising
a bridge circuit having first and second series connected legs connected in parallel with third and fourth series connected legs; -
the first leg of the bridge circuit including an element for sensing mass air flow rate, the element having a resistance which changes with the element'"'"'s temperature; the third leg of the bridge circuit including an ambient air temperature sensing element having a resistance which changes with ambient air temperature; the mass air flow rate sensing element having a particular resistance at a particular temperature which is at least partially determined by the resistance of the ambient air temperature sensing element; means for providing current to the mass air flow rate sensing element including means responsive to bridge circuit imbalances caused by changes in the resistance of the mass air flow rate sensing element for increasing and decreasing the current provided to the mass air flow rate sensing element to maintain the mass air flow rate sensing element at the particular temperature at which the bridge is balanced; means for sensing the current provided to the mass air flow rate sensing element and producing an output signal related to mass air flow rate sensed by the mass air flow rate sensing element; means for sensing changes in the particular resistance of the mass air flow rate sensing element at which the bridge circuit is balanced and producing a correction factor; and means for applying the correction factor to the output signal. - View Dependent Claims (9, 10, 11)
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12. In a bridge type mass air flow rate sensor for providing an output signal related to mass air flow rate, the sensor having a bridge circuit with first and second series connected legs connected in parallel with third and fourth series connected legs, an ambient air
element in a leg of the bridge, the ambient air temperature sensing element having a resistance which changes with temperature, an element for sensing mass air flow rate, the mass air flow rate sensing element having a resistance which changes with temperature, the bridge circuit being balanced when the mass air flow rate sensing element has a resistane corresponding to a particular temperature, the resistance of the mass air flow rate sensing element determined in Part by the resistance of the ambient air temperature sensing element, means for providing current to the mass air flow rate sensing element, the current Providing means including means responsive to imbalances in the bridge circuit caused by changes in the resistance of the mass air flow rate sensing element, for changing the current provided to the mass air flow rate sensing element to maintain the mass air flow rate sensing element at the particular temperature at which the bridge is balanced, means for sensing the current provided to the mass air flow rate sensing element and producing an output signal related to mass air flow rate sensed by the mass air flow rate sensing element, the improvement comprising means for sensing the changes in the resistance of the mass air flow rate sensing element at which the bridge is balanced and producing a correction factor therefrom, and means for applying the correction factor to the output signal.
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13. A mass flow rate sensor (8, 18, 102, 202) for providing an output signal (Vout) related to mass flow rate (m) past the sensor (8, 18, 102, 202) comprising first means (19, 102, 202) for generating a first mass flow rate-related signal (Vb), the first signal (Vb) containing temperature-related errors (e.g., Tl -Ta, Tl -Ts (Ta)) and mass flow rate-related errors (MAS error), second means (R2) for generating a second signal (R2 (Ta)) providing temperature error correction (TCOMP), third means (R1, R4) for generating a third signal (Vc) providing mass flow rate (m) error (MAS error) correction, and means (19;
- 30;
32;
34;
36;
38;
40;
B+;
in FIG. 18;
102;
104;
106;
108;
110;
112; and
in FIG. 22;
202;
204;
206;
208) for operatively coupling the first (19, 102,
202), second (R2) and third (R1, R4) means together to provide the output signal (Vout). - View Dependent Claims (14, 15, 16, 17, 18)
- 30;
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19. A method for providing an output signal (Vout) related to mass flow rate (m) comprising generating a first mass flow rate-related signal (Vb), the first signal (Vb) containing temperature-related errors (e.g., Tl -Ta, Tl -Ts (Ta)) and mass flow rate-related errors (MAS error), generating a second signal (R2 (Ta)) providing temperature error correction (TCOMP), generating a third signal (Vc) providing mass flow rate (m) error (MAS error) correction, and combining (19;
- 30;
32;
34;
36;
38;
40;
B+;
in FIG. 18;
102;
104;
106;
108;
110;
112; and
in FIG. 22;
202;
204;
206;
208) the first (Vb), second (R2 (Ta)) and third (Vc) signals together to provide the output signal (Vout). - View Dependent Claims (20, 21, 22, 23, 24)
- 30;
Specification