Batteries: thermoelectric and photoelectric – Thermoelectric – Thermopile
Reexamination Certificate
1999-07-19
2001-05-29
Gorgos, Kathryn (Department: 1741)
Batteries: thermoelectric and photoelectric
Thermoelectric
Thermopile
C136S233000, C136S242000, C374S179000
Reexamination Certificate
active
06239351
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to the field of thermocouples and in particular to a three-wire self-diagnostic thermocouple which permits detection of calibration changes.
2. Description of the Related Art
A change in the calibration of a thermocouple can cause an error in the detection of the temperature to be determined or controlled. In particular, where equipment is being controlled by a thermocouple, this error could result in the equipment being damaged. Additionally, when the thermocouple controls a process, this error could result in the failure of the process to produce the desired product.
Currently, the accuracy of an installed thermocouple can be assured by placing a second thermocouple of known calibration beside the installed thermocouple and comparing the measured temperatures. This method is not always easy or possible to do and requires periodic checking to be effective. Additionally, it is not conveniently possible to know with certainty which of the two thermocouples is faulty when the two thermocouples indicate different temperatures.
The use of two thermocouple elements within a metal sheath is taught by Burley in U.S. Pat. No. 4,909,855, by Thom et al. in U.S. Pat. No. 4,778,537 and by Hollander in U.S. Pat. No. 5,111,002. Synder Jr. et al. in U.S. Pat. 4,224,461 teach a two wire thermocouple which includes a third wire as a ground wire. Petry in U.S. Pat. No. 2,696,118 teaches a temperature indicating device having two thermocouples in which the two thermocouples have a common element. Further, Bock in Canadian Patent 675,473 teaches that at least four thermocouple junctions are required to eliminate ambiguity from the measured temperature.
SUMMARY OF THE INVENTION
A self-diagnostic thermocouple is disclosed, consisting of a first thermoelement having first thermoelectric output properties, a second thermoelement having second thermoelectric output properties, and a reference thermoelement having stable reference thermoelectric output characteristic. A common junction of the first, second, and reference thermoelement, forms three discrete thermocouple junctions. Preferably, the first, second, and reference thermoelements are enclosed in a sheath and are separated from each other and the sheath by insulating materials.
A first object of the invention is to provide a self-diagnostic thermocouple which can be used to identify when an output of the thermocouple has deteriorated.
A second object of the invention is to provide a three wire thermocouple in which one of the three thermoelements is a reference thermoelement having thermoelectric output characteristics which are stable over time.
Another object of the invention is to provide a self diagnostic thermocouple in which the reference thermoelement is a pure metal such as gold, platinum, iron or copper.
Still another object of the invention is to provide a thermocouple system having a self diagnostic thermocouple and a microprocessor for detecting the deterioration of the thermoelectric properties.
These and other objects will become more apparent from a reading of the specification in conjunction with the appended drawings.
REFERENCES:
patent: 2509825 (1950-06-01), Keyser
patent: 2609406 (1952-09-01), Barsy
patent: 2631220 (1953-03-01), Barsy
patent: 2696118 (1954-12-01), Petry
patent: 3048641 (1962-08-01), Erlebacher
patent: 3232794 (1966-02-01), Korton
patent: 3449174 (1969-06-01), Kleinle
patent: 3845706 (1974-11-01), Strimple et al.
patent: 3973997 (1976-08-01), Solomon
patent: 3980504 (1976-09-01), Wagner
patent: 4224461 (1980-09-01), Snyder, Jr. et al.
patent: 4450314 (1984-05-01), Huther
patent: 4732619 (1988-03-01), Nanigian
patent: 5464485 (1995-11-01), Hall, Jr.
patent: 675473 (1963-12-01), None
Brooks & Kushman P.C.
Gorgos Kathryn
Hoskins Manufacturing Company
Parsons Thomas H
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