Technical Support

Slip Ring and Thermocouple

Industries often need to test and control the temperature of rotary furnace and heating axis, laboratory need to test the thermal properties of new materials, we need to use thermocouples. At the same time the need to observe and record the relevant data, therefore cannot do without this slip ring assembly, but how to choose the slip ring in order to reduce errors to a minimum, which is let engineering personnel headache.

Choosing the wrong slip ring, temperature offset or even exceed the actual amount of temperature change. This article based on years of design experience on thermocouple slip rings, the following summary.

To select the appropriate slip ring, you must first determine the type of temperature measurement system, temperature measurement system common include thermal resistance and thermocouple type, the following is the details on thermocouple:

Thermocouples are among the most commonly used temperature sensing element, thermocouple working principle is based on the Seeback effect, that two different components of the conductor ends connected into the circuit, if two different connection end temperature is in the loop heat generated within the current physical phenomena. Its advantages are:

1) High accuracy, because of a thermocouple in direct contact with the measured object, is not affected by the middle of the media.

2) Wide measurement range. Commonly used thermocouple measurements are sustainable from -50 ~ + 1600 ℃, some special thermocouple lowest measurable to -269 ℃ (such as Gold and Iron nickel-chromium), up to + 2800 ℃ (such as tungsten, rhenium).

3) The structure is simple, easy to use. Thermocouples are usually composed of two different metal filaments, and without size restrictions beginning with the outer protective casing, it is very easy to use.

Thermocouple Fundamentals
Conductor or semiconductor A and B of two different materials welded together to form a closed loop. When the two attachment points exist the temperature difference between 1 and 2, it would produce electromotive force, thus forming a size in the loop current, a phenomenon known as the thermoelectric effect. Thermocouple is to use this effect to work.

Thermocouple Types and Structure Formation
Commonly used thermocouple can be divided into two major categories of non-standard and standard thermocouple. Standard thermocouple refers to the relationship between the national standard thermoelectric power and temperature, tolerance, and a unified standard thermocouple indexing table, it has its support of the display instrument available. Non-standard thermocouple in the range is not more extensive than standard thermocouple, generally there is no uniform indexing table, mainly used to measure certain special occasions.

Thermocouple structure in order to ensure a reliable and stable work, its structure requirements are as follows:
The two heat electrodes which in the thermocouple must be welded firm; should be well insulated from each other to prevent short circuits; compensation wire and the free end of thermocouple connection must be convenient and reliable; protection casing should be able to guarantee heat electrode and harmful media full isolation.

According to the measurement principle is different, the structural and materials of slip ring are different, also include the corresponding control parameters, different requires using different slip ring contact materials, structures and wire to ensure the error to a minimum.

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