Temperature measurement with three-lead resistance thermometers by dual constant current method

Claim 1

A system for measuring a voltage change indicative of the temperature change detected by a three-lead resistance thermometer having three leads including potential leads connected to opposite ends of the resistance thermometer element and a current lead connected to one of said ends, comprising: means for producing constant currents in said element, said potential leads and said current lead such that current of a certain magnitude flows through said element and each of said potential leads and a current of twice said certain magnitude flows through said current lead with the current through each of said potential leads being in the same direction with respect to said element, and voltage measuring means connected between said potential leads to measure the voltage change.

Claim 2

A system for measuring a voltage change indicative of the temperature change detected by a three-lead resistance thermometer having three leads including potential leads connected to opposite ends of the resistance thermometer element and a current lead connected to one of said ends, comprising: means for producing constant currents in said element, said potential leads and said current lead such that current of a certain magnitude flows through said element and each of said potential leads and a current of twice said certain magnitude flows through said current lead with the current through each of said potential leads being in the same direction with respect to said element, and voltage measuring means connected between said potential leads to measure the voltage change.

Claim 7

A system for measuring temperature with a three-lead resistance thermometer having first and second potential leads of equal resistance connecting their terminals to opposite ends of the resistance thermometer element and a current lead connecting its terminal to the end of said resistance thermometer element to which said first potential lead is connected, comprising: a first constant current source connected directly between the terminals of said first and second potential leads and operable to produce a current of a certain magnitude therebetween a second constant current source connected directly between the terminals of said current lead and said first potential lead and operable to produce twice said certain current therebetween in a direction to produce in said first potential lead a net current of said certain magnitude and opposite in direction to that which would result from said first source alone, and a voltage measuring means connected between the terminals of said first and second potential leads so that the voltage measured is related directly to the voltage drop across the resistance thermometer element as an indication of its temperature.

Claim 8

A system for measuring temperature with a three-lead resistance thermometer having first and second potential leads of equal resistance connecting their terminals to opposite ends of the resistance thermometer element and a current lead connecting its terminal to the end of said resistance thermometer element to which said first potential lead is connected, comprising: a first constant current source connected directly between the terminals of said first and second potential leads and operable to produce a current of a certain magnitude therebetween a second constant current source connected directly between the terminals of said current lead and said first potential lead and operable to produce twice said certain current therebetween in a direction to produce in said first potential lead a net current of said certain magnitude and opposite in direction to that which would result from said first source alone, and a voltage measuring means connected between the terminals of said first and second potential leads so that the voltage measured is related directly to the voltage drop across the resistance thermometer element as an indication of its temperature.

Claim 10

A system for measuring temperature with a three-lead resistance thermometer having potential leads of equal resistance connected to opposite ends of the thermometer element and a current lead connected to one of said ends, comprising: a first constant current source connected to the potential leads so as to tend to produce currents of a certain magnitude through said thermometer element and each of said potential leads, a second constant current source connected between said current lead and that one of said potential leads connected to the same end of said thermometer element, said second constant current source being operable to tend to produce current of twice said certain magnitude through the current lead and the potential lead connected to the same end so that the net current flow in said last named potential lead is equal to said certain magnitude and is in a direction with respect to said element that is in correspondence with the direction of flow with respect to said element in the other of said potential leads, and a voltage measuring means connected across said potential leads so that the voltage measured is directly related to the voltage drop across the thermometer element itself as an indication of its temperature.

Claim 11

A system for measuring temperature with a three-lead resistance thermometer having potential leads of equal resistance connected to opposite ends of the thermometer element and a current lead connected to one of said ends, comprising: a first constant current source connected to the potential leads so as to tend to produce currents of a certain magnitude through said thermometer element and each of said potential leads, a second constant current source connected between said current lead and that one of said potential leads connected to the same end of said thermometer element, said second constant current source being operable to tend to produce current of twice said certain magnitude through the current lead and the potential lead connected to the same end so that the net current flow in said last named potential lead is equal to said certain magnitude and is in a direction with respect to said element that is in correspondence with the direction of flow with respect to said element in the other of said potential leads, and a voltage measuring means connected across said potential leads so that the voltage measured is directly related to the voltage drop across the thermometer element itself as an indication of its temperature.

Claim 13

A system for measuring a temperature change with a three-lead resistance thermometer having first and second potential leads connected to opposite ends of the thermometer element and a current lead connected to that end of the thermometer element to which said first potential lead is connected, comprising: a resistor of value corresponding to a base resistance value for said resistance thermometer at a particular temperature, means connecting one end of said resistor to the first potential lead, two constant current sources connected to said second potential lead, said current lead and the other end of said resistor so as to produce currents of a certain magnitude through said thermometer element, each of said potential leads, and said resistor and twice the magnitude of said certain current through the current lead so that said currents in said potential leads are in the same direction with respect to said element, and voltage measuring means connected between the second potential lead and said other end of said resistor so as to measure the voltage change across said resistance thermometer as an indication of the change in temperature of the resistance thermometer from said particular temperature.

Claim 14

A system for measuring a temperature change with a three-lead resistance thermometer having first and second potential leads connected to opposite ends of the thermometer element and a current lead connected to that end of the thermometer element to which said first potential lead is connected, comprising: a resistor of value corresponding to a base resistance value for said resistance thermometer at a particular temperature, means connecting one end of said resistor to the first potential lead, two constant current sources connected to said second potential lead, said current lead and the other end of said resistor so as to produce currents of a certain magnitude through said thermometer element, each of said potential leads, and said resistor and twice the magnitude of said certain current through the current lead so that said currents in said potential leads are in the same direction with respect to said element, and voltage measuring means connected between the second potential lead and said other end of said resistor so as to measure the voltage change across said resistance thermometer as an indication of the change in temperature of the resistance thermometer from said particular temperature.