Question

please anyone tell me which is the most sensetive thermocouple in range 0-50'c giving most output volts???

Answer 1

In all honesty this is a little 'out of my wheelhouse.' But, just to get the ball rolling here I took a quick peek at my copy of 'Lange's Handbook of Chemistry', 13th Edition from 1985. They have a number of tables in Section 11 of this handbook regarding this type of thing. From what I gather: The 'Type E' thermocouples have the greatest Seebeck coefficient (greatest voltage response per degree C) above 0 degrees C of any standard thermocouple. Their data suggests that a Type E, nickel-chromium alloy vs. copper-nickel alloy thermocouple junction voltage is 0.000 mV at 0 degrees C and 3.047 mV at 50 degrees C. FYI: The tables may not have been exhaustive and there may be a much better answer. But, it is a start.

Answer 2

well i thought of iron constantan couple it gives 5.5microvolts/volt is most sensetive :P thanz anyway.

Answer 3

I looked that up in the same reference. (Iron vs. copper-nickel alloy) and it is listed as a type J thermocouple (the most commonly used type in industry due to low cost and relatively high Seebeck coefficient) and it is listed as:
0 degrees C 0.000 mV
50 degrees C 2.585 mV
(And, the tables I am looking at give millivolts as the unit for voltage. The coefficient may be in microvolts, but the values I am giving are total thermoelectric voltage in millivolts.

Answer 4

CRC Handbook 65th edition lists:
Iron-Constantan Thermocouples as having an EMF of 2.58 mV (units are 'absolute millivolts') at 50 deg C
So, it agrees with value from Langes (with less precision). Still cannot find a table for Type E Thermocouple in CRC, yet. (Sometimes the tables are in an odd order in the CRC edition I have.)

Answer 5

i appreciate your help thanx. i want to know something out from tables what books dont know i want to use it in some industrial model any ways thanx alot.

Answer 6

Not that wikipedia is the best source...but at http://en.wikipedia.org/wiki/Thermocouple it lists:
Type E thermocouples have output of around 68 \[muV/C\]
Type J thermocouples have output of around 55 \[muV/C\]

Answer 7

i have seen this i know this table anyway you too would prefer iron-contantan couple for some practical model??

Answer 8

When you are looking at actual applications (instead of a just looking purely at the junction voltage) there are more considerations. There is a good reason the Type J thermocouples are the most common type. Although the Type E does seem to generate a greater voltage at 50 degrees C, there are other, practical issues that limit their usefulness in some applications. Aside from any cost factors (that I did not look up but should be easy to find if you look at a supplier such as Omega Engineering), these include:
Type E thermoelements are useful in oxidizing or inert atmospheres from around -250 deg C to 870 deg C. You need to protect them (with tubes) in atmospheres that are reducing, sulfurous, or alternate between reducing and oxidizing. High temperatures (over 870 deg C) and vacuums should be avoided.
Type J thermoelements are almost as responsive as the Type E and can be used up to around 760 C (use heavier gauge wires above 500 C). They also will usually withstand vacuum, oxidizing, reducing, and inert atmospheres. You should avoid sulfurous atmospheres above 500 deg C and subzero temperatures with this type.

Answer 9

thanx alot you added up my knowledge. . . regards