Like many, our company has a display of old equipment related to our products. In our case, it is a collection of temperature controllers that date back to 1912. I like going by and looking at these old controllers and wondering if the people who designed and developed them had any idea how far temperature control would advance.
Many of these older controllers had hand-wound precision resistors on the circuit boards. Some have deviation meters that show you how close you are to the setpoint. The engineering and design work on some of these older instruments is just amazing. My favorite instrument is an old Leeds and Northrup thermocouple calibrator that was housed in a cherry wood case.
Seeing these old instruments makes me think about how temperature controllers are evolving today. I have been involved in temperature control since 1974. I recall the first microprocessor-based temperature controller that could be programmed. Back in the day, that was pretty amazing.
So, I thought I would get out my crystal ball and see if I could look into the future and see what changes we might see in temperature controllers.
Improved PID Control
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PID control has been around for years. It is a proven mathematical formula that, when set up correctly, works well. But, many manufacturers of temperature control have modified this formula without telling you. Some manufacturers have introduced a feature they call fuzzy logic. This is intended to improve the PID response by introducing “if-then” statements. For example, if the part temperature is warm and the rate of temperature increase is fast, then turn down the heat quickly. The idea is to make the temperature controller begin to “think” like a human.
I believe that we will see more changes to the PID formula. As more powerful microprocessors are used in controllers, it will become easier for manufacturers to add more predictive mathematical models that will provide even better temperature control. Operators will spend less time tuning the system because the controller will be smarter and will learn how the system responds.
Just like cell phones moved from a text-based inputs and display to a touch-based interface and graphic display, so will some temperature controllers. Think of a controller with a touchscreen like your phone, where you swipe your finger across the screen to change parameters. While it is not for everybody, some customers will love the ability to work with a controller that has no buttons.
Likewise, imagine a touch-based controller with Bluetooth communications and an app on your phone. You could walk up to the controller and check it out from your phone. Service people and engineers want to get quick answers as to why the controller is not controlling well. These smart controllers could even send messages if the process was losing control.
I know some of you are cringing at the thought of putting a control device on Wi-Fi, but consider what the medical industry has done. In our local hospital, almost all medical devices are connected in some way to the network. Many of these devices have onboard Wi-Fi and work seamlessly throughout the hospital.
This same concept works in an industrial setting. The controller has Wi-Fi built into it much like a home thermostat does. The controller communicates with a gateway device in the control panel wirelessly, and the gateway device sends the data back to the host computer for analysis wirelessly.
Already, you can buy controllers that will log data. Some of the newer controllers will have a display that looks like a chart recorder. A temperature controller and a chart recorder all in one, with datalogging that can be imported into Excel, would be a powerful temperature controller.
Some controllers are now being offered with Ethernet communications. If you had a controller with Ethernet on board, you can embed a web page into the controller and allow users to set up the instrument with any web browser. A manufacturer can make several web pages that can be used for set up, diagnostics or even trending. Expensive software or specialized communication adapters are needed because any computer with an Ethernet port and a web browser can be used.
PLC and Temperature Control
Ever since Texas Instruments introduced the PM 550 back in the 1980s, PLCs with temperature control capability became possible. But there is a downside to using a PLC to do temperature control. Generally, there is an engineer or two in the plant that is trained and knowledgeable on programming a particular PLC. He is usually pretty busy. The input cards for measuring thermocouples are fairly expensive, and giving operators access to certain parameters within the PLC like tuning the control loop can be difficult.
Recently we have seen a number of temperature control manufacturers begin to integrate multi-loop temperature controllers with PLC functions. These manufacturers began with a temperature control system and added PLC functions, so the system is designed from the ground up to be responsive to temperature control. The software used to program these devices generally is offered for free when you purchase the system, whereas the software used to program a PLC generally costs thousands of dollars.
I can see a future where temperature control manufacturers will begin to offer more powerful controllers that will give you both multi-loop temperature control and PLC functionality in one affordable package. It will be easy to set up and much more cost effective than using a traditional PLC for temperature control.
In conclusion, I believe that the future of temperature control is focused on three areas. First, they will be easier to set up and use. Second, they will perform more tasks than just temperature control. For example, they will have communications that are faster and easier to set up. And third, they will do more background tasks that assist in maintenance. For example, newer controllers may take note of a degrading thermocouple and inform you that you may need to replace your sensor at the next scheduled maintenance.
We have come a long way from a process engineer taking his screwdriver and adjusting the reset on a controller. I cannot wait to see what they come up with next.