Direct reading resistance thermometer

Claim 2

Electrical bridge apparatus for obtaining a direct reading of temperature from a resistance thermometer element having a quadratic temperature-resistance characteristic comprising: a. a first bridge arm containing the said resistance thermometer element, b. a second bridge arm containing a standard resistance, c. adjacent third and fourth arms formed of the primary and secondary windings of a first current comparator of the type having windings on a magnetic core and null detector and current control means for providing ampere-turn balance, one of said windings having a first adjustable tap for varying the turns ratio between primary and secondary, d. a second current comparator formed of a winding on a magnetic core and null detector and current control means for providing ampere-turn balance, said winding being connected across one of said bridge resistances to form a closed loop, e. a second adjustable tap connected to said winding and to the secondary winding of the first comparator for varying the turns ratio between a first portion of the windings and a second portion of the windings, f. a current source connected across said bridge for energization of said bridge, g. a voltage measuring means connected across said bridge for determining bridge balance, h. said first and second taps ganged together and operable such that the bridge gives a reading as determined by the turnsratios of the comparators in terms of a quadratic function of the thermometer resistance.

Claim 3

ApparAtus for obtaining direct temperature reading from a resistance thermometer element having a relationship of temperature to resistance which may be defined by the equation RT R0(1 + AT + BT2) where RT is the resistance of the resistance thermometer element at temperature T, R0 is the resistance of the resistance thermometer at 0* C., and A and B are the two parameters of the quadratic equation expressing the temperature-resistance relationship of the resistance thermometer element, comprising: a. a first current comparator having primary and secondary windings on a core, said primary having an adjustable tap and connected to a constant current source and the said resistance thermometer element in series and said secondary connected to a first variable current source, and null detector means for detecting ampere-turn balance at the comparator and providing a control signal to the variable current source such that the latter provides the necessary secondary current to maintain balance, b. a second current comparator having a winding on a core, said winding having an adjustable tap and connected at the tapping point to the secondary of the first comparator such that the secondary current flows into the comparator dividing into a first channel containing a first portion of the winding and a reference standard resistance and a second channel containing a second portion of the winding and a second variable current source and a null detector for detecting ampere-turn balance at the second comparator and providing a control signal to the second variable current source such that the latter provides the necessary current to maintain balance of the second comparator, c. voltage comparing means connected to the said thermometer resistance element and the said reference standard resistance for determining equal voltage drops across said resistances, and d. ganging means connected between the adjustable tap of the first comparator and the adjustable tap of the second comparator such that the resistance of the thermometer element will be measured directly in terms of temperature according to the given quadratic equation.

Claim 4

ApparAtus for obtaining direct temperature reading from a resistance thermometer element having a relationship of temperature to resistance which may be defined by the equation RT R0(1 + AT + BT2) where RT is the resistance of the resistance thermometer element at temperature T, R0 is the resistance of the resistance thermometer at 0* C., and A and B are the two parameters of the quadratic equation expressing the temperature-resistance relationship of the resistance thermometer element, comprising: a. a first current comparator having primary and secondary windings on a core, said primary having an adjustable tap and connected to a constant current source and the said resistance thermometer element in series and said secondary connected to a first variable current source, and null detector means for detecting ampere-turn balance at the comparator and providing a control signal to the variable current source such that the latter provides the necessary secondary current to maintain balance, b. a second current comparator having a winding on a core, said winding having an adjustable tap and connected at the tapping point to the secondary of the first comparator such that the secondary current flows into the comparator dividing into a first channel containing a first portion of the winding and a reference standard resistance and a second channel containing a second portion of the winding and a second variable current source and a null detector for detecting ampere-turn balance at the second comparator and providing a control signal to the second variable current source such that the latter provides the necessary current to maintain balance of the second comparator, c. voltage comparing means connected to the said thermometer resistance element and the said reference standard resistance for determining equal voltage drops across said resistances, and d. ganging means connected between the adjustable tap of the first comparator and the adjustable tap of the second comparator such that the resistance of the thermometer element will be measured directly in terms of temperature according to the given quadratic equation.

Claim 5

Apparatus for obtaining direct temperature reading from a resistance thermometer element having a relationship of temperature to resistance which may be defined by the equation RT R0 (1 + AT + BT2) where RT is the resistance of the resistance thermometer element at temperature T, R0 is the resistance of the resistance thermometer at 0* C., and A and B are the two parameters of the quadratic equation expressing the temperature-resistance relationship of the resistance thermometer element, comprising: a. a first current comparator having primary and secondary windings on a core, said primary connected to a standard resistance and said secondary having an adjustable tap and connected to a first variable current source, and null detector means for detecting ampere-turn balance at the comparator and providing a control signal to the variable current source such that the latter provides the necessary secondary current to maintain balance, b. a second current comparator having a winding on a core, said winding having an adjustable tap and connected at the tapping point to the secondary of the first comparator such that the secondary current flows into the comparator dividing into a first channel containing a first portion of the winding and the said resistance thermometer element and a second channel containing a second portion of the winding and a second variable current source and a null detector for detecting ampere-turn balance at the second comparator and providing a control signal to the second variable current source such that the latter provides the necessary current to maintain balance of the second comparator, c. a regulated current source connected in the primary or secondary circuits of the first current comparator to energize the said apparatus, d. voltage comparing means connected to the said thermometer resistance element and the said reference standard resistance for determining equal voltage drops across said resistances, and e. ganging means connected between the adjustable tap of the first comparator and the adjustable tap of the second comparator such that the resistance of the thermometer element will be measured directly in terms of temperature according to the given quadratic equation.

Claim 6

Apparatus for obtaining direct temperature reading from a resistance thermometer element having a relationship of temperature to resistance which may be defined by the equation RT R0 (1 + AT + BT2) where RT is the resistance of the resistance thermometer element at temperature T, R0 is the resistance of the resistance thermometer at 0* C., and A and B are the two parameters of the quadratic equation expressing the temperature-resistance relationship of the resistance thermometer element, comprising: a. a first current comparator having primary and secondary windings on a core, said primary connected to a standard resistance and said secondary having an adjustable tap and connected to a first variable current source, and null detector means for detecting ampere-turn balance at the comparator and providing a control signal to the variable current source such that the latter provides the necessary secondary current to maintain balance, b. a second current comparator having a winding on a core, said winding having an adjustable tap and connected at the tapping point to the secondary of the first comparator such that the secondary current flows into the comparator dividing into a first channel containing a first portion of the winding and the said resistance thermometer element and a second channel containing a second portion of the winding and a second variable current source and a null detector for detecting ampere-turn balance at the second comparator and providing a control signal to the second variable current source such that the latter provides the necessary current to maintain balance of the second comparator, c. a regulated current source connected in the primary or secondary circuits of the first current comparator to energize the said apparatus, d. voltage comparing means connected to the said thermometer resistance element and the said reference standard resistance for determining equal voltage drops across said resistances, and e. ganging means connected between the adjustable tap of the first comparator and the adjustable tap of the second comparator such that the resistance of the thermometer element will be measured directly in terms of temperature according to the given quadratic equation.