US5669713A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Calibration of process control temperature transmitter
Assignee: Rosemount Inc
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Filing: 1994-09-27
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Granted: 1997-09-23
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Expires: 2014-09-27
Abstract
Abstract A transmitter in a process control loop measures temperature. A calibrator includes a known calibration element which is connected to the transmitter. Software in the transmitter compares a measured value of the calibration element with the actual value of the calibration element and responsively calibrates the transmitter. The calibrator includes a temperature calibration sensor for coupling to a terminal block of the transmitter. The temperature calibration sensor provides an actual temperature input to the transmitter. The transmitter measures actual temperature of the terminal block and compares actual temperature with a temperature measured by an internal terminal block temperature sensor, and responsively calibrates the internal temperature sensor.
Inventors
- 👤 Bradley N. Schwartz
- 👤 William R. Kirkpatrick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 13:45
CPC Classifications
G; G01; G01K; G01K7/00; G01K7/16; G01K7/18; G01K7/20; G01K15/00; G01K7/02; G01K7/10; G01K7/12; G01K7/13
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
135 words
A temperature transmitter in a process control loop, comprising: a terminal block for receiving a temperature calibration input resistance from a temperature sensor thermally coupled to the terminal block for cold junction compensation calibration; a cold junction compensation temperature sensor coupled to the terminal block for providing an output related to cold junction temperature of the terminal block; A/D conversion circuitry for converting the temperature calibration input resistance and the output related to cold junction temperature into digital values; I/O circuitry coupling to the process control loop and sending and receiving information over the loop; and microprocessor circuitry coupled to the A/D converter for calculating a calibration value for the cold junction compensation temperature sensor based upon the temperature calibration input resistance and the cold junction temperature measured by the cold junction compensation temperature sensor.
Claim 2
Dependent Claim
135 words
A temperature transmitter in a process control loop, comprising: a terminal block for receiving a temperature calibration input resistance from a temperature sensor thermally coupled to the terminal block for cold junction compensation calibration; a cold junction compensation temperature sensor coupled to the terminal block for providing an output related to cold junction temperature of the terminal block; A/D conversion circuitry for converting the temperature calibration input resistance and the output related to cold junction temperature into digital values; I/O circuitry coupling to the process control loop and sending and receiving information over the loop; and microprocessor circuitry coupled to the A/D converter for calculating a calibration value for the cold junction compensation temperature sensor based upon the temperature calibration input resistance and the cold junction temperature measured by the cold junction compensation temperature sensor.
Claim 3
Dependent Claim
12 words
The transmitter of claim 1 wherein the calibration input is NIST traceable.
Claim 4
Dependent Claim
33 words
The transmitter of claim 1 including a resistance coupled in series with the cold junction temperature sensor and wherein the microprocessor determines the cold junction temperature based upon voltage drop across the resistance.
Claim 5
Dependent Claim
84 words
The transmitter of claim 1 including a junction box coupling the sensor input to the temperature sensor, comprising: first connections for coupling to the terminal block of the transmitter in the process control system; second connections for coupling to the temperature sensor; a calibration input for coupling to a reference element; a switch movable between a first position in which the first connections are coupled to the second connections and a second position in which the first connections are coupled to the calibration input.
Claim 6
Dependent Claim
24 words
The transmitter of claim 4 wherein the switch is actuated when the reference element is connected to the calibration input of the junction box.
Claim 7
Dependent Claim
25 words
The transmitter of claim 4 wherein the first connections and the calibration input include four connections for a four-wire resistance measurement of the junction box.
Claim 8
Dependent Claim
158 words
A temperature transmitter in a process control loop, comprising: a terminal block for coupling to a sensor resistance; a current source providing a current through the sensor resistance and through a reference resistance coupled in series with the sensor resistance; an A/D converter which converts voltage differences across the sensor resistance and the reference resistance into digital values; I/O circuitry for sending and receiving information; memory containing a value of the reference resistance R REF and a resistance calibration value R CAL3 ; and a microprocessor receiving an actual value of the sensor resistance from the I/O circuitry, receiving the digital values of the voltage differences across the sensor resistance and the reference resistance from the A/D converter, and receiving the value of the reference resistance R REF from memory and responsively calculating a new calibration value R CAL3 (NEW), wherein R CAL3 (NEW) is stored in the memory as R CAL3 for subsequent use during temperature measurements.
Claim 9
Dependent Claim
158 words
A temperature transmitter in a process control loop, comprising: a terminal block for coupling to a sensor resistance; a current source providing a current through the sensor resistance and through a reference resistance coupled in series with the sensor resistance; an A/D converter which converts voltage differences across the sensor resistance and the reference resistance into digital values; I/O circuitry for sending and receiving information; memory containing a value of the reference resistance R REF and a resistance calibration value R CAL3 ; and a microprocessor receiving an actual value of the sensor resistance from the I/O circuitry, receiving the digital values of the voltage differences across the sensor resistance and the reference resistance from the A/D converter, and receiving the value of the reference resistance R REF from memory and responsively calculating a new calibration value R CAL3 (NEW), wherein R CAL3 (NEW) is stored in the memory as R CAL3 for subsequent use during temperature measurements.
Claim 10
Dependent Claim
87 words
The temperature transmitter of claim 7 wherein the terminal block is adapted for coupling to a thermocouple providing a thermocouple voltage, the memory contains a voltage calibration value V CAL3 and the microprocessor receives an actual value V ACTUAL of the thermocouple voltage, a sensed thermocouple voltage from the A/D converter, and the voltage calibration value V CAL3 and responsively calculates a new voltage calibration value V CAL3 (NEW), wherein V CAL3 (NEW) is stored in the memory as V CAL3 for subsequent use during temperature measurements.
Claim 11
Dependent Claim
82 words
The temperature transmitter of claim 7 including a temperature sensor thermally coupled to the terminal block providing a terminal block temperature sensor output R CJCPRT , and the microprocessor calculates a calibration offset R PRTCAL3 (NEW) in response to the terminal block temperature sensor output R CJCPRT and a probe thermally coupled to the terminal block which provides a resistance R PROBE received by the I/O circuitry, and the calibration offset is stored in the memory for subsequent use during temperature measurements.
Claim 12
Dependent Claim
19 words
The temperature transmitter of claim 9 wherein the probe resistance R PROBE is electrically coupled to the terminal block.
Claim 13
Dependent Claim
20 words
The temperature transmitter of claim 7 including a junction box for electrically coupling the sensor resistance to the terminal block.
Claim 14
Dependent Claim
77 words
The temperature transmitter of claim 11, wherein the junction box comprises: first connections for coupling to the terminal block of the transmitter in the process control system; second connections for coupling to the sensor resistance; a calibration input for coupling to a reference element; a switch movable between a first position in which the first connections are coupled to the second connections and a second position in which the first connections are coupled to the calibration input.
Claim 15
Dependent Claim
25 words
The temperature transmitter of claim 12 wherein the switch is actuated when the reference element is connected to the calibration input of the box junction.
Claim 16
Dependent Claim
26 words
The temperature transmitter of claim 12 wherein the second connections and the calibration input include four connections for a four-wire resistance measurement of the box junction.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-09-22 | 2001-03-24 | 2001-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-09-22 | 2005-03-24 | 2005-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-09-22 | 2009-03-24 | 2009-09-23 | $7700.00 | Window Closed / Lapsed |