JPH0132933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION When measuring temperature using a thermocouple, measurement errors are likely to occur due to heat conduction through the wire and through the protective tube. In particular, it is necessary to reduce thermal conduction errors in contact type surface thermometers that use thermocouples, thermometers that use thermocouples to measure the melting point of a small amount of sample, and the like. In these cases, it is desirable that the protective tube be as thin as possible. It is easier to manufacture a thin tube by inserting only one wire rather than two wires.

In order to reduce the heat conduction error, the temperature gradient at the temperature-measuring junction may be made small, that is, the temperature near the temperature-measuring junction may be made as uniform as possible.

Examples include stainless steel protection tube, chromel,
The case of using an alumel thermocouple will be explained. In the following, chromel will be referred to as a and alumel will be referred to as b.

Embodiment A thermocouple 2 consisting of both wires a and b is placed in a protection tube 1, and the contact point of both wires a and b is welded to one end of the protection tube 1 or a position P near it (FIG. 1). Separately from the above, a strand a is welded to a position Q slightly away from the end P of the protective tube 1 (for example, about 1 cm away). Heating wire 3 for heating the protection tube at position Q
is wound from Q to the opposite side of P.

The temperature difference between the P and Q positions can be detected by a thermocouple consisting of the A wire inside and outside the protection tube and the PQ part of the protection tube 1, so the current in the heating wire 3 can be controlled and Make sure the temperature difference is 0. This makes it possible to significantly reduce thermal conduction errors. The temperature to be measured (temperature at point P) is measured with a thermocouple consisting of both strands a and b inside the protection tube 1. When the temperature to be measured is lower than the ambient temperature, the P and Q portions of the protection tube are cooled in advance to a temperature lower than the temperature to be measured.

In addition, if necessary, move the heating part including position Q into another protection tube.

Example A strand A is put into the protective tube 1 and welded to a position P near one end of the wire (Fig. 2). The strand A and the strand C made of the same material (stainless steel) as the strand B or the protective tube are welded at the same position Q as in the example.

Winding the heating wire 3 is the same as in the embodiment.
The temperature difference between P and Q is detected by a thermocouple made up of the A wire inside and outside the protection tube and the PQ part of the protection tube, so the heating current of the heating wire 3 is controlled by the temperature difference between P and Q. so that the temperature difference between them becomes 0. The temperature to be measured is measured by a thermocouple consisting of an A wire inside the protection tube 1 and a B wire or C wire outside the protection tube. If necessary, precooling and placing the heating wire 3 (including Q) in a separate protection tube are the same as in the embodiment.

In the embodiment, there is a slight temperature difference between P and Q, but there is no problem.

In the embodiment, if the b wire or the c wire is thermoelectrically similar to the material of the protective tube 1, P,
Although there is no problem even if there is a slight temperature difference between Q, it is necessary to keep the temperature difference between P and Q sufficiently small when the temperature is significantly different thermoelectrically.

[Brief explanation of drawings]

Both FIG. 1 and FIG. 2 are explanatory diagrams showing one embodiment of the thermocouple according to the present invention. 1... Protection tube, 2... Thermocouple, 3... Heating wire.

Claims (1)

[Scope of Claims] 1. Insert both wires a and b of the thermocouple into a metal protection tube, connect the contact point of both wires to a point P inside the tip of the protection tube, and connect either of the thermocouple wires to a point P inside the tip of the protection tube. A wire made of the same material as the other wire is joined to a point Q slightly away from point P on the outside of the protection tube, and a heating wire is wound from point Q to the opposite side of the protection tube from point P. , the amount of heating by the heating wire is controlled so that the temperature difference between the two points P and Q detected by the thermocouple consisting of the wires made of the same material inside and outside the protection tube and the portion between P and Q of the protection tube becomes 0. 1. A thermocouple with a protection tube having little error in heat conduction, characterized in that the temperature is measured by a thermocouple made of both the above-mentioned wires a and b inside the protection tube. 2. Insert one wire a of the thermocouple into a metal protection tube, join one end of the wire a to a point P inside the tip of the protection tube, and connect wire a and wire b of the thermocouple. A C wire made of the same material as the protection tube or a material similar to it is placed outside the protection tube at a point Q a little away from point P.
A heating wire is connected to the opposite side of the protection tube from point Q to point P. A device is provided to control the amount of heating by the heating wire so that the temperature difference between the two points P and Q becomes 0, and a thermocouple consisting of the A wire inside the protection tube and the B wire or C wire outside the tube is installed. A thermocouple with a protective tube that measures temperature with little heat conduction error.