DE8331904U1 - HERMETICALLY ENCLOSED TEMPERATURE PROBE WITH SHORT RESPONSE TIME, ESPECIALLY FOR MEASURING SURFACE TEMPERATURES - Google Patents

Description

Description;

Temperature sensor (e.g. Pt 100Λ, Pt 100OiI, semiconductor PTC and -NTC, thermocouples) are usually encapsulated to protect against mechanical damage and aggressive media (TC not always). The encapsulation usually takes place in tubes made of stainless steel, glass or else closed on one side Ceramic that is immersed in the medium to be measured.

This previously used type of protection has the following disadvantages: If the protective tube consists of a poor heat conductors (glass, ceramics, plastics), then the poor heat transport becomes a slow one Adjustment time caused. If, on the other hand, good heat conductors (metals) are used as protective tubes, then the one shown strives The measured value initially quickly counteracts its final value, but then more slowly because the pipe, which is a good conductor, compensates for the temperature with the environment. If there is a high temperature difference between the measuring medium and the environment, so this can lead to bad geometry of the protective tube (short and thick) that the sensor element the end temperature of the measuring medium is never reached. In order to keep this error as small as possible, long, thin measuring sensors are used are used, which in turn are mechanically not very robust and not suitable for surface temperature measurement. For the measurement of surface temperatures, a correction factor is determined experimentally, which, however, strongly contributes the surface properties of the probe and that of the Medium fluctuates. The measured value obtained is therefore subject to great uncertainty.

The aim of the innovation is a robust measuring probe with small dimensions, which despite the small immersion depth in the measuring medium shows an exact measured value, is corrosion-resistant even against aggressive media and is also suitable for Surface temperature measurements.

This goal is achieved with a temperature sensor in which the sensing element has a good heat conductor is connected with good thermal conductivity, which is located in a tube made of a thermally poorly conductive material, with which this good heat conductor is hermetically sealed.

The thermally good conductive heat conductor is preferably made of metal, and the tube is made of thermally poorly conductive The material is preferably made of glass, ceramic or plastic. The good heat conductor can be thermally inserted into the pipe Poorly conductive material melted, glued, cemented or otherwise hermetically sealed to the pipe be tightly connected.

A mechanically very robust and chemically very resistant embodiment is obtained in that a disk made of metal (eg platinum) is melted into the end of a tube made of glass. Good thermal contact is established by contacting the sensor element (Pt 10OQIi, Pt 100OiI ₁ NTC etc.) with the metal disk using thermal paste. The glass tube represents the mechanical connection and, at the same time, the thermal insulation between the measuring medium and the environment.

Further possible embodiments are obtained by using a body made of silver or some other good heat conductor melted, poured, cemented into a tube made of glass, ceramic, plastic or some other poor heat conductor or is glued. The temperature sensor must be connected to the good heat conductor with good thermal conductivity.

With an additional electrical connection to the good heat conductor made of metal, this metal can at the same time serve as a measuring electrode e.g. for the determination of redox potentials, silver or chloride ions.

The innovation is explained in more detail below using a few exemplary embodiments with reference to the drawing.

Fig. 1 is a side section through an embodiment of the innovation. A platinum disc 2 is in one End of the glass tube 3 melted down. The temperature sensor element 1 (here Pt ΙΟΟΛΐη thin film version) is connected to the platinum disk 2 in a thermally conductive manner by means of a thermal paste 4 and a pressure spring 5. For the electrical discharge line 6, the usual embodiments (two-, three- or four-wire technology) are used.

Fig. 2 shows, also in a side section, another embodiment of the innovation. A silver pin 2 is in a Plexiglass tube 3 cemented in. A hole 7 in the silver pin 2 houses the sensor element (NTC) 1, which is made using thermal paste 4 and putty 8 is fastened in this bore 7. With the help of a silicone tube 9 is used for measurements the surface temperature on the material to be measured 10 achieves improved insulation from the environment.

Claims (2)

S.GH G4 SCHOTT-GERÄTE GmbH 6238 Hofheim / Taunus Hermetically encapsulated temperature sensor with short response tent, especially for measuring surface temperature "Protection claims; 1. Temperature sensors, especially for measuring surface temperatures, consisting of a sensor element and a protective tube, characterized in that this Sensor element (1) with a good heat conductor (2) thermally M · ■ is well connected, which is inside this
Protective tube (3) is made of thermally poorly conductive material, with which this good heat conductor is hermetically sealed. 2. Temperature sensor according to claim 1, characterized in that the good heat conductor (2) consists of metal. 3 »temperature sensor according to claim 1 or 2, characterized in that the protective tube from thermally poor
conductive material such as glass, ceramic or plastic.