Temperature sensor and a method of manufacturing the same

Details Temperature sensor and a method of manufacturing the same Temperature sensor and a method of manufacturing the same

1997-07-28

2000-12-26

Gibson, Randy W.

Thermal measuring and testing

Temperature measurement

By electrical or magnetic heat sensor

374140, G01K 700, G01K 112

Patent

active

061648191

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention is related to a temperature sensor using a thermistor of negative temperature coefficient and a method of manufacturing the same.


BACKGROUND OF THE INVENTION

In order to prevent a thermistor of a temperature sensor from indicating a resistance value that is deviating from the value it should have at a certain temperature, in particular in a high temperature zone, the atmosphere around thermistor has to be kept consistent. A prior art as disclosed by Japanese Patent Laid-Open No. 6-307943 teaches to provide a heat resisting cap housing a thermistor with an air ventilation hole.
However, if the ventilation hole is clogged by some reason, it fails to maintain the ambient of a thermistor consistent. The problem that resistance of a thermistor deviates much from a should-be value still remains unsolved.


DISCLOSURE OF THE INVENTION

The present invention is intended to provide a temperature sensor of stable functioning, through a means for preventing a thermistor from indicating a resistance that is deviating from said should-be value even in a high temperature condition.
The invented temperature sensor comprises a heat resisting cap, a thermistor housed inside the heat resisting cap, and at least one lead wire which is electrically coupled with the thermistor and is taken outside the heat resisting cap. The heat resisting cap is made of an alloy containing Ni--Cr as the main ingredient. The above described structure implements a temperature sensor working stable also in a high temperature condition (e.g. 1000.degree. C. or more), thermistor of which sensor indicating a resistance that is not deviating much from the should-be value, without an air ventilation hole or such other contrivance which was needed in a prior art temperature sensor.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a temperature sensor according to an embodiment of the present invention.
FIG. 2 is a cross sectional view showing a temperature sensor according to another embodiment of the present invention.
FIG. 3 is a cross sectional view showing a temperature sensor according to a still other embodiment of the present invention.


BEST MODE FOR CARRYING OUT THE INVENTION

In the following, a temperature sensor according to the present invention and a manufacturing method therefor according to an embodiment are described in detail referring to drawings.
A first embodiment is described with reference to FIG. 1. An (Al,Cr,Fe).sub.2 O.sub.3 system material is formed into a solid body having two holes, into which platinum (Pt) wires 2 are inserted as the electrode, and then sintered together to obtain a thermistor 1. The Pt wires 2 and lead wires 4 of a two-wired tube 3 are welded together respectively, and then a heat resisting cap 5 made of a heat-resistant alloy containing Ni--Fe--Cr as the main ingredient, Inconel-600.TM. is disposed over the thermistor, calked and welded to complete a temperature sensor as shown in FIG. 1.
For testing the durability in high temperature the temperature sensing part of the temperature sensor is kept in a 1100.degree. C. chamber for 10 hours, and resistance values at 900.degree. C. before and after the testing were measured to calculate the rate of resistance shift(%) in accordance with Formula 1. testing-resistance value (.OMEGA.) after testing) .div.(resistance value (.OMEGA.) before testing) Formula 1


TABLE 1 ______________________________________ Resistance value Resistance value Rate of resistance before testing after testing shift ______________________________________ 820.OMEGA. 919.OMEGA. +12% ______________________________________
As Table 1 shows, the resistance value of the temperature sensor according to the present embodiment at 900.degree. C. represents only a slight shift after the 10-hour storage in 1100.degree. C., as compared with the 900.degree. C. value before. It is understood that the temperature sensor can be used also in a high temperature condition over 1000.degree. C.
The invento

REFERENCES:
patent: 4086085 (1978-04-01), McGurty
patent: 4721533 (1988-01-01), Phillippi et al.
patent: 5603571 (1997-02-01), Eckert

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