Most likely you’ve heard about “RTDs”, “Thermocouples”, “Thermistors”, “Semiconductor” type elements and so on, which will be addressed here. Before I go into details of this subject, let’s see what a “Temperature Sensor” (Temperature Transducer) is and what does a “Temperature Transmitter” mean.

Generally, a sensor or transducer is a physical device which is capable of transforming one type of process variable to my favorite signal type. To elaborate on this generalized sentence, let me give you an example. Temperature, pressure, flow, etc, are some process variables and actually, they are physical characteristics of our real world. With modern technology and because of tremendous advances in Electrical Engineering in the past century, we like to transform every measurable process value into an electrical signal and a temperature sensor is a device which will transform the temperature into an electrical signal, no matter how tiny the amount of this signal might be!

So far I took a big “First Step” which was the transformation of “Temperature” into “Electrical Signal”. Based on different sensor technologies, this signal may have different ranges and for industrial applications, I need to have my signals limited to some universally accepted electrical “signal-ranges”. Today some of these globally accepted electrical signal-ranges are 4-20 mA , 1-5 V , 0-10 V , etc.

A “Temperature Transmitter” is a device which transforms the tiny output of a “Temperature Transducer” to one of these standard signal ranges. Now let’s get back to different “Temperature Transducer” technologies. RTD or “Resistance Temperature Detector” is a device the resistance of which varies with the temperature. Since it is a passive device, an external electrical current should be applied to it and then the voltage drop across it can be measured. This voltage is a good indication of the temperature. When referring to such a device as “passive”, it means that the device needs external current (or voltage) source. To state the obvious, a big amount of external current can cause power dissipation in the resistor of RTD and lead to excess heat, so to avoid this type of error, the current should be kept at a minimum level.

There is 2 wire, 3 wire and 4 wire wiring configuration for RTD. More accurate reading calls for 3-wire or 4-wire configurations. In reality, the distance between the temperature sensing point and measuring system calls for wiring and since the real wiring has its own resistance, some measurement error sneaks in hereby! 3-wire and 4-wire solutions are developed to remove this error. One of the most common RTDs is “PT100” which consists of a thin film of Platinum on a plastic film and shows a resistance of 100Ω at 32°F. Its resistance varies with temperature and it can typically measure temperatures from -330 to 1560°F. The relationship between resistance and temperature of PT100 is relatively linear. PT100 is just an example of platinum RTDs and in the industry you may find different RTD types suitable for various applications, e.g.: Copper, Nickel, Nickel-Iron, etc.

Thermistors are temperature-dependent resistors and are widely used in industrial purposes, such as over-current protection, self-regulating heating elements, inrush current limiters and so on. Thermistors can be NTC or PTC. In NTC (Negative Temperature Coefficient) thermistors, resistance decreases as temperature rises. NTC’s are commonly used as “inrush” current limiters. And with PTC (Positive Temperature Coefficient) thermistors, resistance increases as temperature increases. PTC thermistors are commonly used as “overcurrent protection” and in resettable fuses.

A thermocouple or simply “TC” is comprised of a couple of specific dissimilar wires joined together, forming the “sensing point” or “junction”. Based on physical characteristics called “Thermoelectric Effect”, when this junction is placed at different temperatures, different millivolt signals are generated which can be interpreted as an indication of the temperature. In comparison with RTDs, Thermocouples are self-powered and require no external excitation current source. Thermocouples are commonly used for furnaces, Gas Turbine combustion chamber, high-temperature exhaust ducts, etc. The main restriction of Thermocouples is the “accuracy” which doesn’t make it the best solution for precise applications. Also, Thermocouples need a reference measurement point called “Cold Junction”. The thermocouple junction is often exposed to extreme environments, while the cold junction is often mounted near the instrument location. Based on “range” of temperature measurement, “sensitivity” and some other factors in each application, different types of Thermocouples are available, for example E, J, K, M, N, T and so on. For instance, Type “J” is made up  of “Iron-Constantan” combination with a range of −40°F to +1380°F and sensitivity of about 27.8 µV/°F while Type “K” (Chromel-Alumel) is one of the most common general-purpose thermocouples with a sensitivity of approximately 22.8 µV/°F. Type K is inexpensive and a wide variety of probes are available in its −330°F to +2460°F operating range. Since the functionality of thermocouple sis based on Thermoelectric Effect in different types of conductors, when the location of a thermocouple is far from the “measuring instrument” (e.g. electronic transmitter), the proper type of conductors should be used for extension purpose. Otherwise, the tiny signal generated by thermocouple will be added with some error at the point where thermocouple wires are connected to the extension wire! “Semiconductor Temperature Sensor” is based on the fact that the junction voltage across ap-n combination of semiconductors, like a diode junction or “base-emitter” junction of regular transistors, is a function of temperature. This technology is vastly used in electronic devices and IC technologies. Linear characteristic, small size, and low cost are advantages of this technology, but it should be noted that the limited range of around -40°F to 248°F makes it suitable for specific applications. To wrap up this video, the comparison between different types of temperature sensor technologies is a multi-facet task. For example, if “accuracy” is considered as the key performance indicator, usually RTD’s are better than Thermocouples; approximately 10 times more accurate. From the “sensitivity” point of view, while both RTDs and Thermocouples respond quickly to temperature changes, at similar costs, thermocouples are often faster. If I have to measure electronic PCB and/or IC temperature, silicon-based types are the best choices.

In this short article, you will learn what industrial automation is a basic and simplified method.

Ok let’s just say I go into the room and it’s dark. Now what should I do first when I walk into a dark room? Yes, I have to turn on the light. That means I have to press a button on the wall by hand and turn on the light.

Now let’s say instead of changing the wall, I’ll put a sensor in that room. This sensor has a simple open connection within it, like a standard switch.

The way this sensor works is the best way we look in a room and when it sees someone enter the room, the open contact will be closed and then that, the light will flash automatically. When a person leaves the room and there is no one there, the contact will reopen and this time the light will be turned off automatically.

So with this sensor installed, I no longer need to press any button on the wall when I enter or exit a room. With the new system, everything goes automatically, which means that when I enter a room, the sensor automatically kicks off the light and when I leave the room and no one else is there, the light goes out.

Now when we consider lighting a lamp in a room as a process, we can say that when I need to press the switch on the wall, the process happens manually and when the lamp lights up and turns itself off, when someone enters or leaves the room, the process happens automatically. So here I have manual vs automatic. Now what is the difference between the two? The automatic method is also more energy efficient. Because this way when I walk out of the room and no one else is there, the sensor will turn off the light after a few seconds. In this way, I would expect to see real energy savings here too. So this is a basic example of manual vs automatic process.

Now let’s bring the same concept to the factory, manual vs automatic concept. When we are going to produce a product, there is always a first line and a thread. The first line is when the materials enter the factory and the line is where the final product is made and ready to be shipped. Between the first and the last lines, there is a process that transforms the raw material into that final product. So I have a process. Consumables can be considered as the inclusion of this process and the final product can be considered as an output or as a final result.

Now as the process of turning on and off the lamp, this process of factory production, can be done manually or automatically. With the booking process, we can hire a few staff members to do the job but by default, we can set up a system that can take care of the whole production process or at least some parts of it automatically. For example, suppose you start a cake business and want to make your own cakes. To make cakes, you will need a production process where all the necessary ingredients go in when the ingredients and the delicious cake come out as an extract. Now at the beginning of your business, if you are on a tight budget and have few customers, you can hire one or more employees and train them to make cakes based on your recipes.

With this handmade production process, you may be able to make cakes at the right speed and with consistent quality. But as your business grows, trying to make more handmade cakes with high quality compatibility will be very difficult. Why? Because people make mistakes. For example, if one of your co-workers adds one ingredient, that cake will not be the same quality as the other cakes and if this happens too often, your business will start to lose customers and eventually lose money.

Now what should you do to solve this problem? To solve this problem you will need to hire an engineering company to help you transform this cake production process into a default process. With the new automated production process, you will have fewer employees and more equipment. This means that with the new system in place, your equipment will take care of most of the work that has been done by employees before and they will do it quickly, easily and efficiently. So with an automated process, you can make more cakes of the same quality every time and this helps your business grow faster.

The same principles apply to other industries, such as automotive, steel, or oil and gas. In order for these industries to produce the final product according to new standards, they need to have an automated production process. So industrial automation is about big processes, with high quality and consistent accuracy. When we need to produce a product on a large scale with consistent quality at the same time, we need to hire an engineering company to design the automated production process for our business or factory. Many of you have commented that this is the easiest learning environment you’ve ever encountered. I hope you understand what automation is?