AX Control, Inc.

RTDs vs Thermocouples

Working Principles and When to Use Each

This article will focus on the qualities of RTDs vs Thermocouples and their typical applications and principles.

Measuring temperatures in industrial engineering is a key part of monitoring the operation of the various mechanical, electrical, and electronic systems, determining their performance, and evaluating their health.

Likewise, in chemical processes, temperature and heat control may be crucial in achieving the desired end product. Additionally, the same applies to welding, heat treatment processes, industrial ovens used for plastic shrinking, and a wide range of other possible applications. That said, measuring temperatures is neuralgic in a wide range of engineering operations, and doing so with accuracy and precision is equally important.

While there are many types of thermometers that can be used for measuring temperatures including the familiar “mercury” thermometers, the bimetallic, and the vapor pressure thermometers, those that are most commonly and widely used in the industrial environment are the resistance temperature detectors (RTD) and the thermocouple devices. Both of these thermometer types have their respective advantages and drawbacks, and they are both suitable and valuable for a distinctively different set of applications.

Working Principle of Resistance Thermometers (RTD)

The RTD temperature sensor is based on the temperature dependence of the electric resistance of metals. As the temperature increases for metal, so does its electrical resistance. Of course, there’s an intrinsic coefficient of resistance for all materials, and a positive value for this coefficient makes specific materials better than others for the measurement element role. With nickel and platinum, for example, there is near-perfect linearity that is introduced by their respective coefficients, resulting in high accuracy and precision across repeated measurements. Moreover, nickel and platinum are generally chemically stable and extremely resistant to corrosion.

Drawing of a Coil in Tube RTD. Read the article for a breakdown of RTDs vs Thermocouples. — Coil-element Platinum Coil In Tube RTD. Source: Burns Engineering. Licensed Under CC-BY-SA-3.0

Digitalization and Digitization: What’s the Difference?

Close up of digitization/binary code. — Digitization/binary code

If you read industry publications, you’ve probably already come across the terms digitalization and digitization a couple of times today. But do you know the difference?

It’s easy to confuse the terms. But understanding how they differ will help you gain the most information and understanding of the digital mindset.

What is Digitalization?

According to IGI Global, Digitalization is the “adoption of digital technologies to modify a business model….by exploiting digital network dynamics and the giant digital flow of information.” On the other hand, digitalization leads to the creation of a digital business. According to Gartner, this is “the creation of new business designs by blurring the digital and physical worlds.” More about this in a minute.

What’s the Difference between Digitization and Digitalization?

Digitization is where digitalization begins, in the conversion of analog data into a digital form that can be processed by a computer. Digitalization transforms digitized data through the use of digital technologies like automation, computing, coding, AI, or IoT(to name a few) to change how work gets done. And while digitization can optimize and change the process to create a better workflow, reduce costs, or minimize waste, digitalization creates a core change that affects the entire business model.

Modbus: An Introduction to the Protocol

When you’re running a modern factory, you have many machines that need to communicate with each other. These conversations occur over communication protocols that integrate with whatever native ‘language’ the machines speak. However, communications must translate each language to allow other networked devices to understand them. Modbus is one of the protocols that allow this communication to occur.

Modbus gateway I/O module from Reliance Electric. — Modbus Gateway I/O Module from Reliance Electric

What is Modbus?

This is the oldest and most popular of these communication protocols. Published by Modicon in 1979, it was originally used with the company’s programmable logic controllers or PLCs. But Modicon developed Modbus as an open protocol. Anyone could use them for free without licensing. Since its original development many software vendors, manufacturers, and other groups/organizations have supported the protocol.

The communication protocol uses serial lines to send data between devices. This is as simple as a single serial cable connected to serial ports on a Master device and a Slave device. Data moves at 9600 baud (bits per second) as series of zeroes and ones. Each zero or one is a single bit. Data follows regular patterns so 8 bits identifies as a larger byte.

Modbus is a type of SCADA (Supervisory Control and Data Acquisition) automation protocol. It is now owned by Schneider Electric. It is used to help devices and equipment communicate by providing a common language all can understand. This allows for different nodes on the network to interact with request/response type messages.

What Are Modbus Communication Protocol?

The original Modbus interface used serial RS-232 communication. However, as the technology developed, options expanded to include serial RS-485, serial RS-422, and Ethernet. Formatted Ethernet packets embed Modbus messages inside, creating versatile setups. Additionally, networks designed with mixed drops can run different protocols altogether. For example, a single network could run three drops, one using MB Ethernet TCP/IP, another MB RS-232, and a third MB RS-485.