Certainly, it isn’t hard to see why studying the merits of a thermocouple in school is a huge advantage for any serious student who wants to make his mark in the future. It’s but logical. It’s definitely a huge advantage for educational institutions all over the world when they make it a point to include the Seebeck effect-wielding thermal gauge in their curriculum. These educators, without a doubt, are putting the welfare of their students in mind.
Thermocouple: A Most Popular Temperature Sensor
You might think of heat as a bad thing. For most, extreme body heat almost always is associated with being sick. However, in all actuality, heat serves an indispensable purpose in a wide array of industries.
Without heat, we would not be able to mold glass or create steel. The problem, of course, is about control. Too much or too little heat won’t give us the outcome we desire — exactly why we need to monitor the temperature. We can relate to this In the home scene: too much heat would definitely spoil our dinner.
It’s no accident then that the thermocouple has risen to the top of the heat-measuring devices. To boot, the temperature is based on the Seebeck effect alternatively dubbed as the ‘thermoelectric effect’.
- Discovered by German scientist Thomas Johann Seebeck in 1821, the phenomenon shows that a corresponding voltage is produced that is directly proportional to the temperature difference between the joints of two dissimilar electrical conductors (e.g., metals) connected together.
- Usually, the voltages produced via the Seebeck effect are only a few microvolts (i.e., millionths of a volt) but if large arrays of these Seebeck-operating devices are bundled together, considerable electrical power can be produced.
Figure A: K-type thermocouple basic layout (Source)
For sure, other temperature sensors (e.g., RTD, thermistor) can hold their own over thermocouples. Still, the Seebeck-enabled devices reign supreme when it comes to industrial application. Three of the main reasons for its superiority in moving the needle are:
1) Capacity to Measure Extreme Temperature
Arguably, a thermocouple’s ability to measure directly temperatures up to 2600ºC makes it unequaled compared to other temperature sensors. Not even the versatility of an RTD (resistant temperature detector) can top such tremendous capacity. Small wonder why high-temperature applications in metallurgy (e.g., aluminum, steel) benefit from thermocouple use.
2) Extremely Rugged
Thermocouples, right from the onset, are the most robust of all sensor types. The simple design that makes them be vibration-resistant allows them to be used in the most rugged of environments.
That’s because thermocouples don’t have any moving parts and to a large extent nothing fragile.
3) Cheaper and Easy to Manufacture
By a long shot, thermocouples are more economically sound as a temperature probe choice than an RTD or a thermistor. That’s because the electronic contraption is easy to manufacture. So long as you have the right combination of two dissimilar metals joined together, you should be good to go.
As they are inexpensive, thermocouples are the best option in times when you need a slew of sensors for the same application. Take note that some industries would need hundreds, if not thousands, of sensors at one time. An example of this is thermal profiling used in the car industry.
Table A: Difference between Thermocouple, RTDs, and Thermistors
Schools that Make the Most of the Seebeck Effect Sensors
Truth be told, education is meant to prepare us for the real world. Certainly, the best colleges, universities, and technical/vocational schools would be construed as failures if they fail to do that. It’s but logical therefore that those educational institutions that benefit the most from incorporating the study and use of thermocouples in their classes and laboratories are leaning towards production.
For one, many leading educators in modern times have spent quite substantial time and attention on learning the ins and out of the thermocouple. A good example is the 2nd Balkan Region Conference on Engineering Education done in Romania years ago that focused on the study and calibration of thermocouples.
Of course, as massive as the appeal of thermocouples are, knowing their essentials would certainly pose an added advantage to a learner’s skills. Below are key schools that have gained tremendously in the study of these Seebeck-enabled thermal probes:
1) Engineering Schools
Obviously, engineering schools would have to sit atop this list. For one, electrical engineers must be aware of rising temperatures when they want to solicit the most in real power generation. The same holds true for metallurgical engineers who must employ a host of tricks (e.g., smelting, electrolysis, distillation) to process ores and extract needed metals.
Chemical engineering schools would do well to learn the trade too. A distillery or a brewery must have temperatures under control to come up with a suave best-tasting beer or liquor.
Traditionally, there are instances when engineers have used thermocouples as a temperature sensor to come up with a great product. Some of these products are:
- Mining
- Cement
- Paper
- Glass
- Oil/Gas
- Pharmaceutical Products
The automotive industry has also benefited from the use of thermocouples a lot. Not only has it made cars safer but also perform a lot more efficiently. Indeed, there is a slew of specific vehicle applications that make the most of the Seebeck effect-wielding device. Some of these car parts are:
- Surface readings
- Cylinder heads
- Exhaust gas readings
- Spark plugs
- Brake discs
- Car battery
Remember that a motor vehicle is actually expanding heat when it runs on fuel. So, the faster a car goes, the hotter it becomes. It’s therefore imperative that vital car parts be tested to outlast such trying circumstances.
2) Medical Schools
Medical schools may not be fully aware of the use of thermocouples in medical practice. But there’s no doubt about it. The nifty temperature sensor plays a huge role in the comprehensive healing and treatment of patients. To boot, many medical devices use thermocouples in their general electronics.
First up, thermocouples have been used extensively for in vivo diagnostics. Plus, they play a major role in many therapeutic procedures. The two-metal sensors are used to monitor electric currents induced micro-invasively in therapeutic devices.
A classic example is when medical-grade thermocouples are used in:
- treating atrial fibrillation
- treating tachycardia
- measuring tissue temperature during cardiac arrhythmia radiofrequency ablation
3) Food Technology Schools
Food must not only be edible for it to be longed for. It must be delicious. And to do that one must cook the food right. Such a need is even multiplied countless times when you talk about commercial scale.
As future prime movers of the food industry, food tech students must have the foundation in terms of knowledge and skills to feed the masses. So the process of food preparation must be mastered in this regard.
To note, thermocouples are heavily utilized in home food preparation. The oven is one classic example. It regulates temperature using a thermocouple.
On a grander scale, thermocouples along with RTDs *together dubbed as food sensors) ensure the food being prepared is done most efficiently. By doing so, food is protected. It is not undercooked or overcooked. This is especially vital in food cooking methodologies used for mass production and even in low-scale restaurant applications.
Some of the appliances which more often than not use a thermocouple are:
- Fryers
- Warmers
- Ovens
- Grills
- Toasters
Even dishwashers used thermocouples. Furthermore, food inspection systems benefit from the Seebeck effect-based sensors. Food tech students will definitely be able to process food at its finest with a thermocouple probe in hand.
4) Technical/Vocational Schools
Many industries use types of machinery that utilize thermocouples. Thus, professionals who would want to master using such machines would benefit much in learning the ins and outs of the two-metal sensor probe.
Even better, technical and vocational schools all over America that would want to come up with above par repair technicians and maintenance personnel to take care of these types of equipment would fare well to incorporate the study of thermocouples in their curriculum.
Some of these pieces of equipment include:
Injection Molding Machines
Heat is used in molding the majority of thermoplastic materials via the injection molding process. Far too often, thermocouples are placed all throughout this injection molding process to ensure the right temperature is kept.
Extruders
By the same token, type J thermocouples are used in the extruding process. That’s because the heated screw feed is also used in this process, similar to the one used in injection molding. Usually, thermocouples are mounted to monitor the temperature outside of the barrel.
Heat Treating
In metalworking, heat treating is used to alter the physical attributes of the metal. To do that, the furnace must be kept at a predetermined temperature. Thermocouples play a huge role in ensuring such temperatures stay within those parameters.
Annealing Welds
Another method to alter the chemical and physical nature of the metal is by the use of annealing systems. Again, temperatures must be observed to get the process right. To do that, thermocouples are welded to the holding pipe.
Package Machines
Shrink packaging, the most common packaging in the pharmaceutical industry, has been in demand because of its tamper-proof nature. Usually, thermocouples are used in the air circulation heater in the process control for this packaging system.
Choosing the Right Thermocouple
By design, not all thermocouples are created equal. Simply put, different metals come with their own distinct features. Thus, every combination of conductors will produce different results.
It’s important therefore that you carefully select the right thermocouple for your school project. You might think that temperature is the final arbiter as to what kind of thermocouple setup you should be getting. In a way, you’re right. But temperature range isn’t the only thing that matters when choosing the best fit. Here are key questions to ask when zeroing in on the best thermocouple for your application:
1. ) What temperature range will you be using the sensor?
First and foremost you need to look at the temperature range of the material you’d be testing. No doubt, thermocouples have an immense range but take note that not all thermocouples can handle extreme temperatures.
Each combination of metal conductors in a thermocouple has its own particular temperature range. These devices are named by letter depending on the particular metal combination utilized. So to choose the right sensor for your application, make sure you are knowledgeable about what each thermocouple type represents.
Here’s a graph to help you:
Figure B. Most Common Thermocouples and Their Ranges
2.) What is the nature of the environment that you will be testing?
You need to match the sheath type of your thermocouple to the details of the operating environment. Basically, there are three kinds of junctions that you can choose from. These are:
Table B: Thermocouples according to Sheath Type.
Note that there are also surface-mount thermocouples used in the industry. This allows for faster tracking of the surface being monitored. So instead of the sensor being attached to the tip of a particular sheath, the sensor is specifically mounted flush directly to a flat material that is easily fastened to a particular surface under observation.
3.) What is your desired sample rate?
The sample rate is how fast or how slow your need to measure changes in temperature is. If you need to capture temperatures in a very narrow window of time, then you need a thermocouple type with a faster sample rate. However, if you just want to get periodic temperature readings at a normal or slow pace, then an ordinary less expensive thermocouple should suffice.
Table C: Thermocouple Types and Their Quality (source)
Indeed, finding the right thermocouple sensor for your project can be daunting. However, it need not be so. Take a clue from the industries below.
Table D: Thermocouple Types and Their Most Common Industries
Conclusion:
It’s not hard to see why learning the Seebeck effect-wielding temperature sensor is an advantage for any student who wants to succeed in his chosen industry. Without a doubt, the thermocouple is king.