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Turn Heat into Electricity, Then Measure It with a Thermocou
Moderators: AmyCowen, kgudger, bfinio, MadelineB, Moderators
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Jesus1
- Posts: 1
- Joined: Fri Dec 26, 2014 3:35 pm
- Occupation: Student
- Project Question: Problems understanding the Calibration Process of the Thermocouple Thermometer?
- Project Due Date: Past due, given extra time to complete during Holiday Break.
- Project Status: I am just starting
Turn Heat into Electricity, Then Measure It with a Thermocou
I am having problems understanding the calibration of the thermocouple thermometer and I also need assistance with the project in general. Any and all help is appreciated. Thank you in advance.
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SciB
- Expert
- Posts: 2071
- Joined: Fri Feb 01, 2013 7:00 am
- Occupation: Retired molecular biologist, university researcher and teacher
- Project Question: I wish to join Scibuddies to be able to help students achieve the best science project possible and to understand the science behind it.
- Project Due Date: n/a
- Project Status: Not applicable
Re: Turn Heat into Electricity, Then Measure It with a Therm
Hi,
I noticed your query has not been answered so I thought I would try to help you before you run out of time. I’m not an engineer but I do have a basic knowledge of the physics of electricity.
The Background section of the project gives a pretty complete picture of how a thermocouple works but I can see how it could be confusing. The voltage (V) that you measure with the voltmeter is a combination of the V at the probe, which is at the temperature, T, of whatever you are measuring and the V at the meter where the tcouple is connected—room T.
The key to doing the calibration is the table of K-type tcouple voltages for various temperatures that you can access through the link in the project instructions: http://srdata.nist.gov/its90/download/type_k.tab
You will be doing one calibration with the probe in ice water—0 degrees C—and one in boiling water at 100 C. You also need to have an accurate thermometer in order to measure room temperature. So, all you do is put the probe into the ice water, record the room T, record the V-total on the meter (set it for millivolts DC) then look up the V-room for the room T. Once you have all that data, you can calculate the V-junc of the tcouple probe using the equation:
V-junc = V-total + V-room
Now go back to the table of V vs T data and look for the V that you just calculated for the probe. What T does it correspond to? If the tcouple was absolutely accurate the V at 0 degrees C would be 0.00, but since this is just a simple tcouple it may be off by some small amount.
Repeat the calibration with the probe in boiling water. Room T should not have changed but you should always read it and record it just to be safe.
I hope some of the other experts will give their descriptions of the calibration so you can be sure of the accuracy of my interpretation of the project guide.
I think it is really cool that you can get a voltage out of a couple of different metal wires when one end is at a different temperature form the other end. You don’t even need any batteries—just electrons which are everywhere! I think I will get a couple different kinds of metal wire and see if I can make a thermocouple that works.
Good luck!
Sybee
I noticed your query has not been answered so I thought I would try to help you before you run out of time. I’m not an engineer but I do have a basic knowledge of the physics of electricity.
The Background section of the project gives a pretty complete picture of how a thermocouple works but I can see how it could be confusing. The voltage (V) that you measure with the voltmeter is a combination of the V at the probe, which is at the temperature, T, of whatever you are measuring and the V at the meter where the tcouple is connected—room T.
The key to doing the calibration is the table of K-type tcouple voltages for various temperatures that you can access through the link in the project instructions: http://srdata.nist.gov/its90/download/type_k.tab
You will be doing one calibration with the probe in ice water—0 degrees C—and one in boiling water at 100 C. You also need to have an accurate thermometer in order to measure room temperature. So, all you do is put the probe into the ice water, record the room T, record the V-total on the meter (set it for millivolts DC) then look up the V-room for the room T. Once you have all that data, you can calculate the V-junc of the tcouple probe using the equation:
V-junc = V-total + V-room
Now go back to the table of V vs T data and look for the V that you just calculated for the probe. What T does it correspond to? If the tcouple was absolutely accurate the V at 0 degrees C would be 0.00, but since this is just a simple tcouple it may be off by some small amount.
Repeat the calibration with the probe in boiling water. Room T should not have changed but you should always read it and record it just to be safe.
I hope some of the other experts will give their descriptions of the calibration so you can be sure of the accuracy of my interpretation of the project guide.
I think it is really cool that you can get a voltage out of a couple of different metal wires when one end is at a different temperature form the other end. You don’t even need any batteries—just electrons which are everywhere! I think I will get a couple different kinds of metal wire and see if I can make a thermocouple that works.
Good luck!
Sybee