Engineering Insights

TUTCO can provide a wide variety of heater options for many of our product lines. Some of those lesser known but very useful options are distributed wattage heaters, zoned heaters, and dual voltage heaters. They allow for better performance and better control over heaters so you can get the most out of them. 

Distributed Wattage heaters are built to provide different amounts of heat over different sections of a heater while applying voltage to a single set of leadwires or screw terminals. A wattage distribution can be built into most types of heaters though it is most common in cartridge, band and some strip heaters. The purpose of the distributed wattage is usually to attain a better temperature profile (more even temperature) due to sections of a heater exhibiting greater heat loss than other sections.

Winding of resistance wire inside a heater is arranged so that it will produce different wattages over different lengths of the heater (in the case of cartridge heaters) or different wattages over different areas (in the case of band or strip heaters). 

In the case of cartridge heaters, the ends are naturally cooler than the center of the heater, and applying the right wattage distribution to the heater can make the temperature more consistent over a longer length of the heater. The evenness of this temperature profile is most important for sealing applications where an even temperature is required across a sealing bar to provide a good melt across the material being sealed. The more even the temperature profile, the faster the sealing process can operate, which many customers want. There are some common wattage distributions that work in most cases. We call them 35-30-35 and 40-20-40 meaning that the heated length is split into three equal lengths and each section produces 35%, 30% and 35% or 40%, 20% and 40% of the total wattage. Those ‘hotter’ ends of the heater lead to a more even temperature profile. There are plenty of other distributions that a customer may want and they’ll specify the unique wattages and lengths that they’re looking for. 

In the case of band heaters, a hole might be present in a heater to avoid a large bolt or some other obstruction. That obstruction might pull an excessive amount of heat from the heater thereby lowering its temperature near the hole. A distributed wattage can ‘fix’ that by putting more wattage around the hole, thereby producing a heater that generates heat with a more even temperature profile. 

As the name states, a distributed wattage heater is a heater where wattage has been distributed or ‘moved around’ so the heater can provide the best performance for your situation. Zoned heaters are used when you want to be able to control different sections of a heater independently. There are a few different types of zoned heaters. They can be designed as cartridge heaters, most band heaters, and a few types of strip heaters.

In instances when there are two zones, there are typically 2 sets of leads (or screw terminals) where a set consists of two leads, so there are four leads in total. You could consider a band heater built with a flexible hinge option to be a zoned heater if it’s a continuous single heater yet has two sets of screw terminals or leads on either side of the gap. Those zones are operated independently in the same heater. 

With cartridge heaters it can be a little tricker, but in most cases a heater with four leads can be produced and it gives you two zones to control independently, where the heating occurs at each end of the heater. 

If you want a three-zone cartridge heater, that’s more of a challenge but still something we can offer. Due to the nature of the internal components of a cartridge heater we can only design it with 4 leads exiting at most. In that case, one of the leads would be a common lead, and the other three leads would be there for each zone. To control ‘Zone A’ in Figure 3, you would apply voltage from the Common Lead to the leadwire labeled ‘Zone A’. To operate Zones B and C, you would apply voltage between the Common Lead and the corresponding leadwire. All three zones can be operated simultaneously, and independently.

It should be noted that a three-phase power source cannot be used with this type of heater because you cannot adjust the voltage of each leg of a 3-phase power source, nor turn any of them off independently.

Zoned heaters give you the options to control separate sections of a heater as if they were their own separate heaters.

Dual Voltage heaters are built so that they can operate at one of two voltages and produce the same wattage over the entire length of

the heater in both scenarios. A bit of clever wiring is how we build
these types of heaters. This is helpful if a heater will be operated in the US and Europe and the customer needs to be able to account for that, by a simple wiring change. Dual voltage heaters (as either cartridge or band heaters) are built with 3 leadwires or screw terminals and voltage is applied either between only two of the connection points, ignoring the third, such as 1 and 3 in Figure 4 below or to that third terminal (2) and the other two terminals (1 and 3) connected together. It should be noted that dual voltage configurations are only possible when one voltage is exactly twice or exactly half of the other voltage. 110V/220V is a good combination, as is 230V/460V, but something like 110V/230V or 230V/480V is not possible.

For situations where you need to account for your applications being operated by possibly two different voltages, consider using a dual voltage heater.

As you can see there are several electric configuration options available that you may not be aware of or may have never taken advantage of. Consider the options available when you want to get the best performance out of your heaters.

Measure temperature and the use of temperature scales have played a pivotal role in human history, aiding in scientific discoveries, technological advancements, and everyday life. Over the centuries, various temperature scales have been developed, each with its unique origin and applications. In this article, we will explore four different temperature scales, Fahrenheit, Celsius, Kelvin, and Rankine, tracing their historical origins and delving into their modern day uses.

The Fahrenheit Scale (°F)
The Fahrenheit scale was created by Daniel Gabriel Fahrenheit in 1724. He was Polish, of German decent. At the age of 15 he moved to the Netherlands where he lived the rest of his life. His scale is one of the oldest temperature scales still in use today. Fahrenheit initially based his scale on the temperature of a brine of ice, water, and salt. He assigned 0°F to the lowest temperature he could achieve using this mixture, and 92°F or 96°F to the average human body temperature, depending on which historical source you choose. The scale was adjusted slightly so that there would be 180 degrees between the freezing and boiling points of water. That explains why we see them as such unusual numbers as 32°F and 212°F.

The Fahrenheit scale was the common temperature scale in most English speaking countries until the 1960s at which time it was replaced with the Celsius scale over a period of about a decade. The scale remains popular in the United States where it has been used for weather measurements for many years, as well as for cooking and baking measurements. It is preferred in the United States primarily for historical reasons and familiarity. It might be seen in the UK where degrees Fahrenheit might appear alongside degrees Celsius on the news or in newspapers, regarding weather temperatures. The only other countries that use the Fahrenheit scale on a regular basis are the Cayman Islands and Liberia. Some scientific research fields, such as chemistry and engineering, continue to use the Fahrenheit scale for specific applications.

The Celsius Scale (°C)
The Celsius scale was developed by Swedish astronomer Anders Celsius in 1742. Celsius originally defined 0°C as the boiling point of water and 100°C as the freezing point of water, which is backwards from today’s conversion. This scale was later inverted to its current form by either the Carl Linnaeus (Swedish, in 1745) or Jean-Pierre Christin (French, in 1777), depending on your source of history. With that inversion in place the scale was called the “forward Celsius scale” for a while before the ‘forward’ was dropped.

It should be noted that craftsman Pierre Casati, under the direction of Jean-Pierre Christin, built the first mercury filled thermometer. It provided much better accuracy and repeatability than the alcohol based thermometer that was in use until then.

Outside of Sweden, it was called the Centigrade scale (from the Latin centum, meaning 100, and gradus, meaning steps), but that had its own problems. In French, Centigrade was already a word that meant one hundredth of a gradient, which is an angular measurement. The name Centesimal degree was tried for a while but that caused problems in the French and Spanish languages, meaning one hundredth of a right angle. In 1948 the world changed the name to Celsius in honor of its inventor.

In 1972, however, Australia was still using Centigrade in their televised weather forecasts. It wasn’t until February of 1985 that it was mandated that all measurements must be given in degrees Celsius. The Celsius scale gained widespread adoption in Europe and most of the world. Its simplicity and alignment with the freezing and boiling points of water making it ideal for most scientific purposes. When it comes to standardization, Celsius has been through a heck of a run.

The Kelvin Scale (K)
The Kelvin scale, named after the Scottish physicist Lord Kelvin (William Thomson), was developed in the mid-19th century. Unlike the Fahrenheit and Celsius scales, the Kelvin scale is an absolute temperature scale, starting from absolute zero or 0 K (-273.15°C or -459.67°F). Absolute zero is the theoretical temperature at which all molecular movement stops or a system has zero thermal energy. There is no temperature lower than 0 K, meaning there are no negative numbers on the Kelvin scale.

The Kelvin scale revolutionized the study of heat. It provided a fundamental framework for understanding the behavior of gases and the laws of thermodynamics. The scale is primarily used in scientific and engineering disciplines, such as physics, chemistry, and engineering, where reference to an absolute zero value is critical. It is an essential scale for research involving extreme temperatures, such as in cryogenics and (strangely enough) high-temperature physics.

The Kelvin scale is one of the few temperature scales that isn’t marked in degrees. There are no degrees Kelvin or °K. It’s not 293 degrees Kelvin or 293 °K, but simply 293 K or 293 Kelvin. 293 Kelvins (the common plural) is acceptable too, though not preferred.

The Kelvin scale and Celsius scale are related. The size of a step in each scale is exactly the same. If it’s 20°C (293.15 K) outside, and the temperature goes down by 1°C, the temperature in Kelvin goes down by 1 Kelvin to 292.15 K. That makes conversion between the two temperature scales very easy. K = °C + 273.15 and °C = K-273.15.

Some interesting information about absolute zero and how absolute it really is….The average temperature of the universe (remembering that it’s mostly empty space) is 2.3 Kelvin, with areas like the Boomerang Nebula in the Centaurus constellation at a chillier 1 Kelvin. That’s about as cold is at gets.

But not quite. In August of 2021, the lowest temperature ever achieved in a laboratory was 38 picokelvins or 38 trillionths of a Kelvin (0.000000000038 K) using a cloud of rubidium atoms, a magnetic field, a vacuum, and putting the equipment into freefall to eliminate the effect of gravity. Now that’s COLD. The temperature was achieved for about 2 seconds.

The Rankine Scale (°R)
The Rankine scale is named after the Scottish engineer and physicist William John Macquorn Rankine. It is another absolute temperature scale developed in the 19th century though it is the rarest of the four scales discussed here. It is similar to the Fahrenheit scale but starts from absolute zero, meaning that a step in temperature in the Rankine Scale is the same size as a step in temperature in the Fahrenheit scale. Just as the Kelvin scale has no negative numbers, neither does the Rankine scale because its 0°R is absolute zero.

The Rankine scale is used in engineering applications, particularly in the United States and sometimes the UK. Much like Kelvin, it provides a convenient absolute temperature scale for calculations involving gases and thermodynamics. It is used where calculations are performed using imperial units instead of metric units (as with the Kelvin scale). Some specific engineering disciplines are thermodynamics, fluid mechanics, and refrigeration.

Since it is a temperature scale based on absolute zero, the National Institute of Standards and Technology (NIST) advises against using the degree symbol (°) when citing Rankine temperatures, though that is often not the case and degrees (°R) are used. I

Here’s a bonus temperature scale to discuss; the Réaumur scale (°Ré)
The Réaumur temperature scale, denoted as °Ré, is a historical temperature scale named after René-Antoine Ferchault de Réaumur, a French scientist who introduced it in 1730. The Réaumur scale was widely used in Europe during the 18th and 19th centuries, particularly in France,  where it was developed. Unlike modern temperature scales like Celsius and Fahrenheit, the Réaumur scale had specific applications. More on that later. His scale was based on the freezing and boiling points of water set at 0 °Ré and 80° Ré, respectively. The scale divided this range into 80 equal parts. Réaumur thermometer was alcohol based (look at the year, it was 1730!), so it was not as accurate as today’s thermometers.

The Réaumur scale found applications primarily in the cheese industry, used for the cheese-making processes. Cheese production is highly sensitive to temperature control, and the Réaumur scale provided a convenient reference for cheese makers at the time. Cheese-making involves several temperature-dependent steps such as milk pasteurization, curd formation, and fermentation. The Réaumur scale allowed cheese makers to monitor and control these processes accurately (at the time), and repeatedly. Specific cheeses like Camembert and Brie, for instance, require precise temperature control during maturation. Cheese makers could use the Réaumur thermometer to maintain the appropriate conditions. At the time, the Réaumur scale was revolutionary.

Its limitations became apparent, though, as scientific understanding and temperature measurement technology advanced. The Réaumur temperature scale did not account for temperature behavior at extreme values (being alcohol based), and over time it lacked universality, making it less suitable for modern, globalized industries.

As temperature measurement standards evolved, it was largely replaced by the Celsius scale, which offered greater precision and general acceptance. While the Réaumur scale is no longer the primary choice in cheese production, it is rumored to be found in use by a few cheesemakers in a few remote valleys in Switzerland and Italy. It remains a part of the historical heritage of temperature measurement.

While doing research for this document, the author discovered 73 different temperature scales that had been developed over the years, the vast majority of which are now obsolete. They were created for many different applications, and some were completely incorrect.

A scale called the Wedgwood scale (°W), for example, was used for temperatures above the boiling point of mercury (673°F). It’s purpose was in the fields of pottery, glass making and metallurgy where the scale would be used to measure the temperature of kilns. The only problem was, they had the temperature of the boiling point of mercury incorrect (by a lot!), so their scale was useless. It fell out of favor very quickly!

A most peculiar temperature scale that still exists today, but is mostly unused, is the Planck scale, named after the German physicists Max Planck. It ranges from 0 to 1 Plancks, and that’s it. There’s nothing outside that range. 0 is absolute zero and 1 is the hottest temperature ever achievable in the universe, believed to be ≈2.555 hundred thousand trillion trillion trillion °F.

Temperature scales have evolved over centuries, with each having their unique historical origins and applications. While Fahrenheit, Celsius, Kelvin, and Rankine serve different purposes and are used in various fields, they all contribute to our understanding of temperature and its impact on the world around us. Whether measuring the weather, conducting scientific research, or designing engineering systems, these temperature scales continue to play a crucial role in our lives.