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aliz_khanz
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okie so cyrogenic processor is one thing but there has to be some phenomenon which is used to measure cyrogenic temperature?
luke1970 said:Using a piece of equiptment delicate enough to observe the electron movement is one way, and probably the most effective.
In the range between 13.81 and 903.89 K...a platinum resistance thermometer is used as the interpolating instrument [between various levels of the IPTS, which has various phase-transition based "official" temperatures]...Below 13.81 K no precisely defined procedure has been agreed. In the range between 5.2 and 13.81 K various scales based on the vapor pressure of hydrogen are in practical use. Below 5.12 K...down to about .3 K the 1958 and 1962 helium scales are widely used as de facto extensions of IPTS 1968
but can't i find a proper method , on when to claibrate , which special thermometers or diodes are used and how they function ? Thanks for your help !f95toli said:I am not sure I understand your question.
All you need in order to measure low temperatures is a thermometer.
A thermometer designed to be used at or near room temperature (300K) will obviously not work very well at cryogenic temperatures, but that is to a large extent because it is not calibrated (and the materials used are not ideal for very low temperatures).
Some temperature sensors that are used at low temperatures (silicon diodes), work quite OK even well above room temperature.
Now, measuring VERY low temperatures (below say 0.3K) is somewhat trickier, but -180 degrees C can be measured even with something as simple as a 50p schottky diode as long as you calibrate it first, all you need to do is to bias it as some current and then measure how the voltage changes with temperature.
edit: Take a look at the following webpage
http://www.lakeshore.com/temp/sen/smindex.html
Lakeshore is one of the biggest suppliers of temperature sensors and e.g. their DT470 Si diode is widely used (I am in fact installing one in a probe tomorrow)
If you don't need 50mK accuracy and repeatability, you could probably find a Pt RTD for about half that price.f95toli said:That said, it is not really that complicated. Just buy a sensor suitable for the temperature range you are interested in from e.g. Lakeshore (see the link above). A sensor that follows a standard resistance vs. temperature curve (which is usually accurate enough) costs something like $200.
Very low temperatures, such as -180K, are typically measured using specialized instruments called cryogenic thermometers. These thermometers use the properties of materials at extremely cold temperatures to accurately measure the temperature.
The principle behind measuring very low temperatures is based on thermal expansion. As the temperature decreases, the volume of a gas or liquid also decreases. This change in volume can be measured and converted into a temperature reading.
Materials that are commonly used to measure very low temperatures include helium, hydrogen, and various metals such as platinum and copper. These materials exhibit unique properties at extremely low temperatures that make them ideal for temperature measurement.
The accuracy of measurements of very low temperatures can vary depending on the instrument and technique used. Cryogenic thermometers can typically measure temperatures with an accuracy of 0.1 K or better, while other techniques such as nuclear magnetic resonance can achieve accuracies of 0.001 K or better.
Yes, there are some challenges and limitations to measuring very low temperatures. One of the main challenges is ensuring that the temperature of the measurement device does not interfere with the temperature being measured. This can be overcome by carefully controlling the temperature of the device and using specialized techniques such as adiabatic demagnetization. Additionally, some materials may become solid or change their properties at extremely low temperatures, making it difficult to accurately measure their temperature.