Process fluid temperature measurement
First Claim
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1. An apparatus for measuring a temperature of a process fluid comprising:
- a resistance based temperature (RTD) sensor configuration to thermally couple to the process fluid;
first and third electrical connections configured to apply a current through an RTD;
second and fourth electrical connections configured to measure a voltage across the RTD; and
measurement circuitry configured to identify a degraded connection if at least one of the connections to the RTD becomes degraded and responsively measure a temperature of the process fluid using less than all of the first, second, third and fourth electrical connections, wherein the degraded connection is detected based upon comparing monitored resistance or residual EMF for each of the first, second, third and fourth connections with resistance or residual EMF of the other of the first, second, third and fourth connections.
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Abstract
An apparatus for measuring a temperature of a process fluid includes a resistance based temperature sensor (RTD) sensor configured to thermally couple to the process fluid. First and second electrical connections are configured to apply a current through the RTD. Measurement circuitry is configured to measure a voltage across the RTD and identify a degraded connection to the RTD and responsively measure a temperature of the process fluid using the electrical connections.
22 Citations
21 Claims
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1. An apparatus for measuring a temperature of a process fluid comprising:
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a resistance based temperature (RTD) sensor configuration to thermally couple to the process fluid; first and third electrical connections configured to apply a current through an RTD; second and fourth electrical connections configured to measure a voltage across the RTD; and measurement circuitry configured to identify a degraded connection if at least one of the connections to the RTD becomes degraded and responsively measure a temperature of the process fluid using less than all of the first, second, third and fourth electrical connections, wherein the degraded connection is detected based upon comparing monitored resistance or residual EMF for each of the first, second, third and fourth connections with resistance or residual EMF of the other of the first, second, third and fourth connections. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of sensing temperature of a process fluid, comprising:
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thermally coupling a resistance based temperature sensor (RTD) to the process fluid; causing a current to flow through the RTD using a first and third connection to the RTD; measuring a voltage across the RTD using a second and a fourth connection to the RTD; identifying a degraded connection to the RTD based upon a change in EMF or line resistance; and responsively measuring a temperature of the process fluid using less than all of the first, second, third and fourth connections to the RTD when a degraded connection is detected, wherein the RTD degraded connection is detected based upon comparing monitored resistance or residual EMF for each of the first, second, third and fourth connections with resistance or residual EMF of the other of the first, second, third and fourth connections. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification