DE102007011022B3 - Immersion thermocouple for measuring temperature of molten steel, has platinum layers arranged on ceramic carriers, serving at adjustment position, and including side with thermo-wires and another side with connecting leads - Google Patents

Abstract

The thermocouple has thermo-wires (2.1, 2.2) attached to a junction (1). The thermo-wires lead to two ceramic carriers (3.1, 3.2) on which platinum layers (4.1, 4.2) are arranged. The platinum layers serve at an adjustment position, and have a side with the thermo-wires and another side with connecting leads (5.1, 5.2). The thermo-wires and the ceramic carriers are arranged in a protective pipe that is connected to a front side. The protective pipe is made of quartz or alumina. The protective pipe is arranged in a housing and fastened with a grouting.

Description

The The invention relates to an immersion thermocouple in which a connection point thermocouple wires are connected.

The inventive arrangement can be used to measure temperatures greater than 1,500 ° C become. Preferred field of application is the measurement of the temperature of molten steel.

With Thermocouples can measured temperatures with simple means and electronically evaluated without the need for external energy sources.

thermocouples are components that are made of two different and one end interconnected metals or semiconductors. At the open End, an electrical voltage is generated when the junction and the free ends are exposed to different temperatures.

There every metal and every alloy has a thermoelectric coefficient usually owns is given relative to platinum, can from the thermoelectric voltage of the Metal pairing of a thermocouple at the junction prevailing temperature are calculated.

at the selection of a material pairing for measurement purposes one strives for high thermoelectric voltage, high linearity and high corrosion resistance low oxidation at high temperatures. These goals are not reachable with a single combination. Therefore, depending on Purpose used different material pairings.

Far Common thermocouple pairs are made of nickel - chrome / nickel (Type K, most common Type) and platinum - platinum / rhodium (Type S; for high temperatures). For the measurements of high temperatures (T> 1600 ° C) are also iridium-iridium / rhodium thermocouples, for the measurement low temperatures (T <-250 ° C) gold / iron-nickel / chromium or gold / iron-gold / silver thermocouples used.

Around Keeping costs low are common between liaison offices and free ends compensating lines made of less expensive materials used. For applications For high temperature measurement, these materials are because of their low Melting point not suitable. For these applications need therefore platinum wires used, which are carried out very thinly for cost savings. For example be for Thermocouples used for temperature measurements on steel melts be, wires from 30 ... 40 mm in length used with diameters of 50 um. Because of these thermocouples melt at very high temperatures after a short time and therefore can only be used once, is a cost reduction for the costly platinum balance leads of great importance. A further reduction of the wire diameter separates because of the then no longer sufficient durability.

Out DE-AS 12 94 516 is a thermocouple assembly is known which has two thermocouples, which are fused together at the hot spot. The hot spot is the part of the thermocouple that is exposed to the temperature to be measured. On the thighs are lead wires, which lead to measuring instruments attached. An insulating and protective jacket covers part of the legs and the leads. The shell is made of a refractory metal and is filled with an insulating material that keeps the legs and leads within the shell spaced apart and insulated.

Furthermore, in DE-OS 25 55 441 describes an arrangement in which a measurement circuit can be assigned to a certain temperature of the voltage generated by a thermocouple in a suitable manner. Hereby, temperature changes at the cold junction are compensated for by providing a compensating reference resistor in the form of a temperature-sensitive resistor material on a printed circuit board, which in turn bears against an isothermal plate in such a way that the resistor contacts the isothermal plate, each time surrounds the terminals.

For use at very high temperatures, these arrangements are not suitable.

Of the The invention is therefore based on the object, one for use at high temperatures suitable arrangement to create a Cost reduction compared allows known arrangements.

The The object is achieved according to the invention with a compensation line, which has the features specified in claim 1, solved.

advantageous Embodiments are specified in the subclaims.

at the inventive arrangement to lead short thermo wires to two ceramic carriers, on which platinum layers are arranged on one side with the compensating cables and on the opposite side with connecting wires are provided.

Especially It is advantageous that uses very short compensation lines can be for example, only one length of 5 ... 10 mm.

advantageous Embodiments provide that the arrangement of the ceramic carrier with the platinum layers and the connection point and the connecting wires in one are arranged on the front closed protective tube. The Platinum layers can Be covered and act as a low-cost high-temperature compensation line, since the layer only 1 micron can be fat.

Especially suitable are protective tubes made of quartz or aluminum oxide.

A expedient embodiment sees in that the protective tube is arranged in a housing in which it is attached with a potting.

The Invention will be explained in more detail below with reference to an embodiment.

In the associated Show drawing:

1 a sectional view of the thermocouple assembly and

2 a section through the entire measuring arrangement.

1 explains the thermocouple assembly. The connection point 1 consists of a PtRh6 / PtRh30 arrangement with the compensation cables connected to it 2.1 and 2.2 , The compensation lines 2.1 and 2.2 have a length of 5 ... 10 mm and lead to the platinum layers 4.1 and 4.2 , The platinum layers 4.1 and 4.2 are as thin layers of about 1 micron thickness on the ceramic substrate 3.1 and 3.2 evaporated. As a ceramic carrier 3.1 and 3.2 serve about 1 ... 2 mm thick and 30 ... 40 mm long ceramic strips. On the cold side are the platinum layers 4.1 and 4.2 with inexpensive connecting wires 5.1 and 5.2 connected, which consist of nickel, silver or another material.

In 2 the entire measuring arrangement is shown. The in the description of 1 explained thermocouple assembly is of a protective tube 6 surrounded by quartz or alumina, which in a housing 7 is arranged. In the case 7 are the components in a potting 8th , which consists for example of a protective cement layer attached. The connecting wires 5.1 and 5.2 connect the platinum layers 4.1 and 4.2 with the pins 9.1 and 9.2 ,

1

junction

2

compensation line

3

ceramic carrier

4

platinum layer

5

Lead wire

6

thermowell

7

casing

8th

grouting

9

pin

Claims (4)

Immersion thermocouple, in which a connection point ( 1 ) Thermo wires ( 2.1 . 2.2 ), characterized in that the thermo wires ( 2.1 . 2.2 ) to two ceramic carriers ( 3.1 . 3.2 ), on which platinum layers ( 4.1 . 4.2 ) are arranged, which serve as a compensation point and on one side with the thermo wires ( 2.1 . 2.2 ) and on an opposite side with connecting wires ( 5.1 . 5.2 ) are provided. Immersion thermocouple according to claim 1, characterized in that the connection point ( 1 ), the thermocouple wires ( 2.1 . 2.2 ) and the ceramic carriers ( 3.1 . 3.2 ) in a protective tube closed at the front ( 6 ) are arranged. Immersion thermocouple according to claim 2, characterized in that the protective tube ( 6 ) consists of quartz or aluminum oxide. Immersion thermocouple according to claim 3, characterized in that the protective tube ( 6 ) in a housing ( 7 ), in which it is sealed with a potting ( 8th ) is attached.