Measured-value transducer with a compensating bridge circuit

Claim 2

A measuring-transducer circuit arrangement suitable for a two-line telemetering system, the arrangement comprising: a bridge circuit having a compensating resistor and having two bridge diagonals; a current regulator; a resistor arrangement including at least one resistor; said current regulator and said resistor arrangement being connected in a series path with one of said bridge diagonals, said current regulator being directly connected on one side of said bridge circuit adjacent to said compensating resistor and said resistor arrangement being directly connected to the other side of said bridge circuit; a measuring amplifier connected to the other of said bridge diagonals and having an output; a circuit path connecting said output of said measuring amplifier to said compensating resistor and said measuring amplifier controlling a compensating current which in use flows in said compensating resistor; said current regulator being connected in a loop through which said compensating current flows; means to derive a control signal in dependence upon the voltage across said one resistor in said resistor arrangement and to supply said control signal to said current regulator to maintain said voltage substantially constant; and a direct voltage supply common to both said bridge circuit and said measuring amplifier.

Claim 3

A measuring-transducer circuit arrangement according to claim 1 wherein said one resistor arrangement comprises only said resistor.

Claim 4

A measuring-transducer circuit arrangement according to claim 1 wherein said means to derive a control siGnal comprises means to provide a fixed reference voltage, and a comparator for controlling said current regulator in dependence on the comparison of the voltage across said one resistor in said resistor arrangement with said reference voltage.

Claim 5

A measuring-transducer circuit arrangement according to claim 1 wherein said current regulator comprises two transistors connected in Darlington configuration.

Claim 6

A measuring-transducer circuit arrangement suitable for a two-line telemetering system, the arrangement comprising: a thermocouple element forming said measuring transducer; a bridge circuit including a compensating resistor and having two bridge diagonals; a current regulator; a resistor arrangement including at least one resistor; said current regulator and said resistor arrangement being connected in a series path with one of said bridge diagonals, said current regulator being directly connected on one side of said bridge circuit adjacent to said compensating resistor and said resistor arrangement being directly connected on the other side of said bridge circuit; a measuring amplifier connected in series with said thermocouple element to said other of said bridge diagonals and having an output; a circuit path connecting said output of said measuring amplifier to said compensating resistor and said measuring amplifier controlling a compensating current which in use flows in said compensating resistor; said current regulator being connected in a loop through which said compensating current flows; means to derive a control signal in dependence upon the voltage across said resistor in said resistor arrangement and to supply said control signal to said current regulator to maintain said voltage substantially constant; and a direct voltage supply common to both said bridge circuit and said measuring amplifier; said bridge circuit further including resistors of such values that the operating voltage of said bridge circuit is in the range of the same order of magnitude to the next higher order of magnitude as the maximum output voltage of said thermocouple element.

Claim 7

A measuring-transducer circuit arrangement suitable for a two-line telemetering system, the arrangement comprising: a thermocouple element forming said measuring transducer; a bridge circuit including a compensating resistor and having two bridge diagonals; a current regulator; a resistor arrangement including at least one resistor; said current regulator and said resistor arrangement being connected in a series path with one of said bridge diagonals, said current regulator being directly connected on one side of said bridge circuit adjacent to said compensating resistor and said resistor arrangement being directly connected on the other side of said bridge circuit; a measuring amplifier connected in series with said thermocouple element to said other of said bridge diagonals and having an output; a circuit path connecting said output of said measuring amplifier to said compensating resistor and said measuring amplifier controlling a compensating current which in use flows in said compensating resistor; said current regulator being connected in a loop through which said compensating current flows; means to derive a control signal in dependence upon the voltage across said resistor in said resistor arrangement and to supply said control signal to said current regulator to maintain said voltage substantially constant; and a direct voltage supply common to both said bridge circuit and said measuring amplifier; said bridge circuit further including resistors of such values that the operating voltage of said bridge circuit is in the range of the same order of magnitude to the next higher order of magnitude as the maximum output voltage of said thermocouple element.

Claim 8

A measuring-transducer according to claim 5 wherein two of said resistors forming said bridge circuit are temperature-dependent resistors, said two resistors being disposed in respective diagonally opposite branches of said bridge circuit.