Most work thermocouples are type K or N because they are relatively inexpensive and can be replaced frequently. They are capable of measuring temperatures as high as F C , but degrade rapidly when cycled above F and should be used only once above that temperature. The thermocouples are usually made of beads and splines over bare wire type because it is difficult to find sheath materials that remain flexible at these higher temperatures.
Relative life expectancy for both the platinum- and tungsten-grade thermocouples fabricated as mentioned above is low due to factors such as exposure to the vacuum furnace environment, high temperatures and the necessity of handling between cycles. Another approach to work temperature measurement at the higher temperature ranges is to use long, rigid-construction thermocouples fed down through the hot zone into the workspace as shown in Fig.
The thermocouples in this example are type S material with alumina protection tubes, but this approach could be used with the other platinum thermocouple types and tungsten-rhenium material.
These thermocouples must be removed from the workspace, either automatically or manually for load insertion and removal. Control and over-temperature limit thermocouples are usually located near the heating elements in the hot zone, but outside the boundaries of the workspace. The important thing to remember is that the location of the control thermocouple junction in relation to the heating elements affects the average temperature of the work as measured by the work thermocouples.
The junction of the thermocouple extends past the heating elements, the distance being determined by hot zone design. However, when running furnace surveys, the average temperature of the survey thermocouples can be increased by pulling the control thermocouple out, closer to the plane of the heating elements.
The average temperature decreases if the control thermocouple is pushed farther into the hot zone. Flexible work thermocouples are generally placed in the load but masked from seeing the direct radiation of the heating elements. Direct radiation tends to make the work thermocouples read incorrectly. The thermocouples are usually placed inside slugs or scrap parts with holes drilled in them to provide shielding.
Keep in mind that when using thermocouples with twisted junctions, the measuring junction is not at the extreme end of the thermocouple, but is at the last twist before the wires go into the insulating material.
This area must be shielded to get good readings. Work thermocouples are frequently provided with quick-connects that plug into a jack panel located just outside of the hot zone Fig. This makes it very convenient to place the thermocouples in the load before it is put into the furnace and then plugging the thermocouples into the jack panel after the furnace is loaded. The one negative aspect to this approach is that the jack panel is usually located in an area where temperatures can range from to F to C during operation.
The jack panel selected must be rated for high-temperature operation. In addition, one must be careful to have no dissimilar metal junctions in this area, because the introduction of a secondary junction will create an error in the thermocouple reading. In applications where contaminants are out-gassing from the load, the jack panel connection is subject to contamination, which can introduce errors into the measurement. So if you took an infrared camera to a vacuum would it show up as the temperature of the room or what?
What will the IR camera see? It should be kept cold, so that it can more easily sense thermal IR. The IR that hits it will be largely absorbed. The time it takes to get an image is very long compared to the time it takes light to reach the camera from the opposite wall.
So the image will depend not on the thermal equilibrium IR density which depends only on temperature but rather on the IR emissions from the wall. The more absorptive, the more they will show up.
Sorry, let me rephrase my question. I was wondering more of what it would feel like. Let's just say hypothetically that I could stick my arm into a vacuum. What would it feel like because I just can't wrap my head around no temperature. I think it wouldn't feel very hot or cold. So there's a net flow of radiant heat out from your arm to the room.
If there were air in the room, there would also be some convective cooling of your arm by the air. So not having the air around should make your arm feel a bit warmer than it would otherwise. Of course the lack of pressure from the vacuum will feel weird. I'm not sure if it would pop blood vessels or something. But that's another issue. I still want to ask, what is the temperature of vacuum?
The real one, with nothing in it. No elements, no radiation, no magnetic or other fields. If there is no electromagnetic radiation then the temperature would be absolute zero. The third law of thermodynamics says that's not reachable. So the vacuum you describe is not "the real one" but an unattainable ideal one. It's fair to say, however, that as the density of thermal radiation approaches zero the temperature assuming the radiation can be described by a thermal spectrum approaches 0 K.
I know there is a limit on how small a volume is that we can refer to, but still, if i look at a volume very small, smaller than the size of particles we know, wouldn't that volume be considered as vacuum, the "ideal" one you were talking about? And another thing troubles me, when we look at the position of matter as a probability function of space we find that a particle is spread all over the place, so in what sense are the walls of a vacuum cell not filling it up with themselves?
Many of our particles electrons, muons, neutrinos, quarks, That means that one could have their wave functions squashed in more and more, at least until things start to happen beyond our current laws of physics. Those would be things like the formation of tiny black holes for which the as yet undeveloped quantum theory of gravity would be needed. That's not the sort of event which would be called "nothing".
So I don't know of any way you can describe a piece of space so small that it has to be empty. Some of the books on string theory might be a good place to start looking at what people are trying to do about small-scale physics. The walls of a box will indeed have some quantum spread, just like anything else. However, the magnitude of the quantum wave typically falls off exponentially with a characteristic distance scale of less than an angstrom, so you have effectively none in the bulk of the box.
Following Sergei's question regarding an "ideal" vacuum with absolutely no form of matter or energy just plain space-fabric : I've learned that the temperature of something is the average kinetic energy of its particles, which is to say the total kinetic energy divided by the number of particles. What you learned is wrong. There are certain familiar special cases where the "energy per particle" definition of absolute temperature isn't too bad. However, in general that definition breaks down in serious ways.
In a vacuum, if you choose to call photons particles, the very number of the particles depends on temperature, going as T 3. The average energy per photon does still go as T. In many other cases, e. At low T, the thermal energy in a piece of diamond goes as T 4 , not T. The thermal energy per particle is then much less than kT at low T. Hence i think it is pointless to say "the temperature of vacuum", although electromagnetic waves can travel through it, but that doesn't mean vacuum does indeed have a temperature.
The thermal radiation has U and it has S. When it's got a thermal spectrum, it has a defined T. Connect and share knowledge within a single location that is structured and easy to search. In vacuum there are only a few molecules so measuring their kinetic energy is very hard, because vacuum has a very little heat capacity and the thermometer with much higher heat capacity will interfere with measurement.
I guess the heat transport will be slow too, because heat conduction and convection will be negligable and only heat radiation will transport energy between the wall of the vacuum container and the thermometer. Is there a better way to measure temperature in vacuum?
The temperature of a true vacuum would be a measure for the energy distribution of the photon gas in that vacuum. You can derive the occupation of the electromagnetic modes in a volume with Bose-Einstein statistics, which is essentially what Planck did to describe the emission spectrum of a black body. However, you don't need to do understand the details of this derivation, because the photon gas will be in thermal equilibrium with the vessel walls.
So, stick a thermometer with a high-emissivity surface e. This will even work if the walls are very far away, or not there at all, like in outer space. The temperature of the thermometer will gradually approach the temperature of the photon gas. Oftmals wird, insbesondere bei komplexen Geometrien der Bauteile, eine Zweifach- oder Dreifachrotation realisiert.
Dies macht es schwierig Temperatursensoren direkt an den zu beschichtenden Bauteilen anzubringen. During coating, the components to be coated are frequently moved to produce a homogeneous layer.
Often, especially with complex geometries of the components, a double or triple rotation is realized. This makes it difficult to attach temperature sensors directly to the components to be coated.
Measurement of the substrate temperature with infrared sensors from the outside: The temperature of the passing substrates is measured by means of infrared temperature measuring devices through a special window, which is transparent to IR radiation. The disadvantages of this temperature measuring method in this context are mainly the following:. Messung mit Thermoelementen in der Kammer: 2. Measurement with thermocouples in the chamber:.
Co-rotating thermocouples: The thermocouple must be mounted on the substrate carrier and the cables of the thermocouple must be led through a rotary feedthrough from the vacuum receiver. Such a measurement usually reflects the substrate temperature very well, but the cost of the rotary feedthrough is considerable. Stationary thermocouples: A thermocouple is mounted stationary in the chamber statically between vacuum chamber walls and moving substrate.
According to the state of the art, the corresponding measurement, both in terms of time and in terms of absolute temperature, gives limited results with limited accuracy. In order to obtain reasonably accurate measurement results, it is necessary to wait until the vacuum chamber and the substrates are in thermal equilibrium.
Experience also shows that the measurement result depends heavily on the position of the sensor. Aufgabe der Erfindung Object of the invention. It is desirable to be able to rely on thermosensors mounted stationary in the vacuum chamber.
In this case, a measurement method is to be specified, which provides over the prior art more reliable values Solution of the task. The reference shields the temperature sensor from the environment in such a way that only radiation reaches the surface of the temperature sensor, which comes from surfaces of the reference and which comes from surfaces whose temperature is to be determined. For example, this can be achieved by making the reference cup-shaped, at the bottom of which the surface of the temperature sensor is thermally insulated from one another, and the cup is oriented so that its opening points in the direction of the substrates to be measured.
Beschreibung der Erfindung Description of the invention. In the theoretical case of infinitely extended surfaces, if the sensor surface is located between the reference surface and the substrate surface and the system is in thermal equilibrium, the temperatures of substrate, sensor and reference surface behave as follows:. Thus, the substrate temperature at known temperature of the reference surface and measured temperature of the sensor temperature of the sensor surface can be determined by the simple relationship of Equation 1.
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