Fault detection system for transducers

Claim 2

A fault detection system for transducers comprising: first aand second transducers, each of said transducers being adapted to receive alternating current; said first transducer including means responsive to a first variable condition for providing a first direct current signal which varies with said first variable condition; a common conductor; means for coupling the common conductor to said first and second transducers whereby said first direct current signal can be applied to the common conductor; the alternating current from said first and second transducers tending to cancel each other out during normal operation of the first and second transducers whereby the current amplitude on said common conductor is relatively low under normal operation of the first and second transducers and increases at least to a predetermined amplitude in response to a failure of one of said first and second transducers; said first direct current signal being of a lower amplitude than said predetermined direct current amplitude; and failure detection means coupled to said common conductor and responsive to the current amplitude on said common conductor being at least at said predetermined amplitude to provide a failure signal.

Claim 3

A fault detection system as defined in claim 1 including first and second alternating current sources coupled, respectively, to said first and second transducers, the voltage of the power provided by each of said sources being substantially equal.

Claim 4

A fault detection system as defined in claim 2 wherein the alternating current provided by each of said sources is substantially oppositely phased.

Claim 5

A fault detection system as defined in claim 1 wherein said failure detection means is directly coupled to said common conductor.

Claim 6

A fault detection system as defined in claim 1 wherein each of said first and second transducers has two conductors leading to such transducers.

Claim 7

A fault detection system as defined in claim 1 wherein said failure detection means includes a sensing resistor coupled to the common conductor and means coupled to the common conductor and responsive to the voltage drop across said sensing resistor reaching a predetermined magnitude for providing said failure signal.

Claim 8

A fault detection system as defined in claim 6 wherein the resistance of said sensing resistor is substantially less than the impedance of either of said transducers.

Claim 9

A fault detection system as defined in claim 1, wherein said predetermined amplitude includes a predetermined alternating current amplitude, said failure detection means being responsive to either of said predetermined direct current or predetermined alternating current amplitudes to provide a failure signal.

Claim 10

A fault detection system as defined in claim 1 wherein said first variable condition is the position of a movable element and said means of said first transducer is responsive to the position of the movable element.

Claim 11

A fault detection system for transducers comprising: first and second transducers, each of said transducers being adapted to receive electrical power; said first transducer including means responsive to a first variable condition for providing a first current signal which varies with said first variable condition, the first current signal being smaller than the current required to power said first transducer; said second transducer including means responsive to a second variable condition for providing a second current signal which varies with said second variable condition, the second current signal being smaller than the current required to power said second transducer; first means coupled to said first transducer and responsive to the first current signal for providing a detection signal related to said first variable condition; second means coupled to said second transducer and responsive to the second current signal for providing a detection signal related to the second variable condition; a failure detector coupled to said first and second transducers whereby the failure detector is coupled to receive current from the first and second transducers, the current from said first and second transducers tending to cancel each other out during normal operation of the transducers whereby the current at the failure detector increases at least to a predetermined level in response to a failure of one of the transducers; and said failure detector including means responsive to the current being at least at said predetermined level for providing a failure signal.

Claim 12

A fault detection system for transducers comprising: first and second transducers, each of said transducers being adapted to receive electrical power; said first transducer including means responsive to a first variable condition for providing a first current signal which varies with said first variable condition, the first current signal being smaller than the current required to power said first transducer; said second transducer including means responsive to a second variable condition for providing a second current signal which varies with said second variable condition, the second current signal being smaller than the current required to power said second transducer; first means coupled to said first transducer and responsive to the first current signal for providing a detection signal related to said first variable condition; second means coupled to said second transducer and responsive to the second current signal for providing a detection signal related to the second variable condition; a failure detector coupled to said first and second transducers whereby the failure detector is coupled to receive current from the first and second transducers, the current from said first and second transducers tending to cancel each other out during normal operation of the transducers whereby the current at the failure detector increases at least to a predetermined level in response to a failure of one of the transducers; and said failure detector including means responsive to the current being at least at said predetermined level for providing a failure signal.

Claim 13

A fault detection system as defined in claim 10 including means for supplying alternating current to said first and second transducers, the alternating current from said first and second transducers being substantially oppositely phased, a common conductor coupled to said first and second transducers and to said failure detector whereby the current level on said common conductor is relatively low during normal operation and increases to at least said predetermined level upon the occurrence of said failure, said means for providing a failure signal being directly coupled to said common conductor.