Sensor failure or abnormality detecting system incorporated in a physical or dynamic quantity detecting apparatus

A pressure sensor comprising:

• a semiconductor substrate having a diaphragm portion;
• and
• a pressure detecting bridge circuit comprising gauge resistors having resistance values varying in response to a pressure applied on said diaphragm portion of said semiconductor substrate,
• wherein said gauge resistors are constituted by separate gauge resistors, and
• a failure judgement of said pressure detecting bridge circuit is performed based on a voltage difference between two midpoints of said pressure detecting bridge circuit as well as a voltage difference between a pair of intermediate terminals selected from intermediate terminals of said separate gauge resisters, said selected pair of intermediate terminals having the same voltage level in a condition where no pressure is applied on said diaphragm portion.

A pressure sensor comprising:

• a semiconductor substrate having a diaphragm portion;
• and
• a pressure detecting bridge circuit comprising gauge resistors having resistance values varying in response to a pressure applied on said diaphragm portion of said semiconductor substrate,
• wherein a failure judgement of said pressure detecting bridge circuit is performed based on voltage differences between one and the other terminals of said bridge circuit and first and second intermediate terminals of said bridge circuit.

A pressure sensor comprising:

• a semiconductor substrate having a diaphragm portion;
• a pressure detecting bridge circuit for outputting an electric signal representing a pressure applied on said diaphragm portion of said semiconductor substrate, said pressure detecting bridge circuit comprising two gauge resistors provided in a first direction and two other gauge resistors provided in a second direction normal to said first direction;
• a failure detecting circuit, provided at a predetermined region of said diaphragm portion where said pressure detecting bridge circuit is not formed, for outputting an electric signal in response to the pressure applied on said diaphragm portion, said failure detecting circuit having a sensitivity different from that of said pressure detecting bridge circuit;
• failure judging means for performing a failure judgement of said pressure detecting bridge circuit based on the output signals of said pressure detecting bridge circuit and said failure detecting circuit.

A pressure sensor comprising:

• a sensor chip constituted by a semiconductor substrate with a diaphragm portion;
• a pedestal on which said sensor chip is adhered;
• and
• a reference pressure chamber formed between said sensor chip and said pedestal,
• wherein a pressure detecting bridge circuit consisting of gauge resistors is formed on said diaphragm portion to output an electric signal representing a pressure applied on said diaphragm portion,
• a failure detecting bridge circuit consisting of gauge resistors is formed on a specific region of said diaphragm portion different from said pressure detecting bridge circuit, said failure detecting bridge circuit outputting an electric signal responsive to said pressure applied on said diaphragm portion, and
• a sensitivity of said failure detecting bridge circuit is higher than a sensitivity of said pressure detecting bridge circuit.

A pressure sensor comprising:

• a diaphragm portion;
• a reference pressure chamber isolated by said diaphragm portion;
• an output circuit for outputting an electric signal representing a pressure applied on said diaphragm portion by using pressure detecting elements formed on said diaphragm portion or in a peripheral region of said diaphragm portion;
• and
• judging means for detecting an abnormal situation that a reference pressure in said reference pressure chamber becomes equal to an outside pressure of said diaphragm portion.

A pressure sensor comprising:

• a diaphragm portion;
• a reference pressure chamber isolated by said diaphragm portion;
• a pressure detecting circuit for outputting an electric signal representing a pressure applied on said diaphragm portion by using pressure detecting elements formed on said diaphragm portion or in a peripheral region of said diaphragm portion;
• and
• a failure detecting circuit for outputting an electric signal representing said pressure applied on said diaphragm portion, said failure detecting circuit having a higher sensitivity than that of said pressure detecting circuit.

A sensor abnormality detecting circuit for a sensor having a first output terminal generating a first output voltage and a second output terminal generating a second output voltage, said first output voltage and said second output voltage varying in mutually opposed positive and negative directions in response to a sensed physical quantity by the same voltage amount with respect to a predetermined equilibrium voltage, said sensor abnormality detecting circuit comprising:

• a reference voltage generating circuit for generating a reference voltage substantially identical with said equilibrium voltage;
• an operational amplifier having one input terminal receiving said reference voltage generated from said reference voltage generating circuit;
• a first resistor having one end receiving said first output voltage of said sensor and the other end connected to the other input terminal of said operational amplifier;
• a second resistor having one end receiving said second output voltage of said sensor and the other end connected to the other input terminal of said operational amplifier, said second resistor having the same resistance as that of said first resistor;
• a third resistor connected between an output terminal of said operational amplifier and the other input terminal of said operational amplifier;
• and
• a judging circuit for generating an abnormal signal notifying an occurrence of sensor abnormality when an output voltage of said operational amplifier is outside a predetermined normal voltage range.

A sensor abnormality detecting circuit for a sensor having a first output terminal generating a first output voltage and a second output terminal generating a second output voltage, said first output voltage and said second output voltage varying in mutually opposed positive and negative directions in response to a sensed physical quantity by the same voltage amount with respect to a predetermined equilibrium voltage, said sensor abnormality detecting circuit comprising:

• a reference voltage generating circuit for generating a reference voltage substantially identical with said equilibrium voltage;
• an operational amplifier having one input terminal receiving said reference voltage generated from said reference voltage generating circuit;
• a first differential amplifier having a non-inverting input terminal receiving said first output voltage of said sensor and an inverting input terminal receiving the reference voltage generated from said reference voltage generating circuit;
• a second differential amplifier having a non-inverting input terminal receiving said second output voltage of said sensor and an inverting input terminal receiving the reference voltage generated from said reference voltage generating circuit;
• a first resistor having one end receiving an output voltage of said first differential amplifier and the other end connected to the other input terminal of said operational amplifier;
• a second resistor having one end receiving an output voltage of said second differential amplifier and the other end connected to the other input terminal of said operational amplifier, said second resistor having the same resistance as that of said first resistor;
• a third resistor connected between an output terminal of said operational amplifier and the other input terminal of said operational amplifier;
• and
• a judging circuit for generating an abnormal signal notifying an occurrence of sensor abnormality when an output voltage of said operational amplifier is outside a predetermined normal voltage range.

A pressure sensor comprising:

• a semiconductor substrate having first and second diaphragm portions;
• a pressure detecting circuit provided on said first diaphragm portion for outputting an electric signal responsive to a pressure applied on said first diaphragm portion;
• a failure detecting circuit provided on said second diaphragm portion for outputting an electric signal responsive to a pressure applied on said second diaphragm portion, said failure detecting circuit having a sensitivity higher than that of said pressure detecting circuit;
• and
• failure judging means for performing a failure judgement of said pressure detecting circuit based on output signals of said pressure detecting circuit and said failure detecting circuit.

A dynamic quantity detecting sensor comprising:

• a sensing portion having sensitivity varying in response to an applied voltage or an applied current;
• a signal processing circuit for processing an output of said sensing portion to generate an output signal representing the output of said sensing portion;
• a first sample hold circuit for holding an output signal of said signal processing circuit;
• an operational processing circuit for processing an output signal of said sample hold circuit responsive to a first impressed voltage or a first impressed current applied to said sensing portion as well as an output of said signal processing circuit responsive to a second impressed voltage or a second impressed current applied to said sensing portion;
• and
• a judging circuit for performing an abnormality detection based on the processing result of said operational processing circuit.

A pressure detecting apparatus comprising:

• a diaphragm for receiving a pressure;
• a plurality of piezoelectric resistors formed on a surface of said diaphragm, each of said plurality of piezoelectric resistors having a resistance value varying in accordance with a distortion of said diaphragm;
• and
• a sensing circuit comprising a first bridge circuit and a second bridge circuit each constituted by said plurality of piezoelectric resistors,
• wherein said first bridge circuit generates a first bridge output representing the distortion of said diaphragm caused when the pressure is applied on said diaphragm;
• and
• the plurality of piezoelectric resistors of said second bridge circuit are connected in a predetermined relationship so as to generate a second bridge output which does not change in response to the distortion of said diaphragm.

A pressure sensor comprising:

• a diaphragm deformable in response to a pressure applied thereon;
• and
• a plurality of gauge resistors generating an electric signal representing said applied pressure based on a distortion of said diaphragm, wherein
• said gauge resistors includes at least six gauge resistors each having a resistance value varying in accordance with said applied pressure,
• said six gauge resistors consist of incremental gauge resistors and decremental gauge resistors electrically connected, each of said incremental gauge resistors having a resistance value increasing in accordance with said applied pressure and each of said decremental gauge resistors having a resistance value decreasing in accordance with said applied pressure,
• said electric signal representing said applied pressure is produced based on a voltage difference between two predetermined points of a plurality of connecting points of said six gauge resistors, and a sensor failure is detected based on a voltage difference between two another points of said connecting points.

A pressure sensor comprising:

• a diaphragm deformable in response to a pressure applied thereon;
• and
• a plurality of gauge resistors generating an electric signal representing said applied pressure based on a distortion of said diaphragm, wherein
• said gauge resistors includes at least first to six resistors each having a resistance value varying in accordance with said applied pressure,
• said first gauge resistor is connected to a second gauge resistor at a first connecting point, said second gauge resistor is connected to a third gauge resistor at a second connecting point, said third gauge resistor is connected to a fourth gauge resistor at a third connecting point, said fourth gauge resistor is connected to a fifth gauge resistor at a fourth connecting point, said fifth gauge resistor is connected to a sixth gauge resistor at a fifth connecting point, and said sixth gauge resistor is connected to said first gauge resistor at a sixth connecting point,
• said first and fifth gauge resistors cause resistance changes in the same direction when said pressure is applied on said diaphragm while said second and sixth gauge resistors cause resistance changes in the opposed direction when said pressure is applied on said diaphragm,
• said third and fourth gauge resistors cause resistance changes in the same direction when said pressure is applied on said diaphragm,
• said electric signal representing said applied pressure is produced based on a voltage difference between said first and fifth connecting points caused when a voltage or current is supplied between said third and sixth connecting points, while a sensor failure is detected based on a voltage difference between said second and fourth connecting points.