Temperature controller selection 5 major considerations

1, display and man-machine interface
When choosing a controller, a key decision is "what kind of user interaction I need." If the application requires very little user interaction, a controller with basic display capabilities is usually sufficient. For example, a simple seven-segment LED display has the advantage that the controller's display is clear and supports long-distance reading.


A controller with text and graphical displays is more appropriate if the characteristics of the application determine the need for a large amount of user interaction, such as frequent setpoint changes, periodic adjustments, access to process information, or running programs. This type of controller supports text labels that match the machine's work, making process data easier to understand, rather than displaying confusing code.


Graphic displays can display information through pictures, charts, and icons in a format that conforms to conventional logic, making user interaction easier. In addition, the graphic display can generally hide certain parameters and settings, or display an interface on the main operation interface, further reducing the complexity.


2, control performance
The next step is to choose the type of control that best fits your application needs. If the level of adjustment required for the application is high, the user should select the PID (proportional-integral-derivative) controller; if only basic control functions are required, then ON-OFF control (switch control) is sufficient. Today, most controllers support both operations, but the type of control still needs to be carefully considered.


In addition to heating control, many modern controllers can achieve cooling control through secondary outputs so that when process materials or products are not cooled naturally, you can perform forced cooling, such as starting a cooling fan, turning off the heat source instead of waiting for the temperature to drop naturally. . Heating and cooling in this type of controller share a PID parameter, but still does not provide sufficient control for some applications, so some of the more complex controllers provide a separate PID setting for the cooling function.
 
Currently, auto-tuning is becoming standard on controllers, but what users typically need is a simple adjustment to a particular application. Controllers with advanced features allow you to minimize overshoot or apply settings quickly; others have adaptive adjustments that react quickly to any interference.
 
3, interface technology
System accuracy is the next priority. Some applications, such as heat treatment, set the system accuracy for the entire setpoint range, in which case the input accuracy becomes very important. Equipment accuracy can reach 0.1% when high levels of input accuracy are required. For general applications, the most common input accuracy is 0.25.


The sampling rate of the sensor input (referred to as the measuring frequency of the sensor) is also a major factor to consider, but since the temperature rise and fall cycles are long, the sampling rate is not critical for temperature control. However, when measuring fast-reacting variables (such as pressure values that can suddenly rise or fall), you need to quickly control response speed and faster input.
 
On the input side, the most important thing is to make sure the controller supports the sensors you use. Controllers generally support most standard thermocouples or PT100 sensors with universal inputs. If it is an infrared sensor or a special type of thermocouple, you may need to double check that your controller is available. In addition, you must also consider the output device you need to drive: a simple controller with a relay output is less expensive, but its switching frequency is very limited due to mechanical wear, so if you need faster or more frequent switching operations, It is best to use a controller that supports SSR (Solid State Relay) output. Finally, you can choose a linear output that can control other types of variables other than temperature, such as valve or thyristor switching devices.
 
You also need to consider other features from the controller, for example, an analyzer can help you achieve temperature changes over time. You can choose a simple analyzer to set the ramp rate and maintain temperature or program multiple process and set temperature range with a single timer.
 
4, structure and installation
Another key is whether you install the controller on the front panel or the back of the front panel. The advantage of front panel mounting is the complete display, which is easy to install and easy to access - easy to remove and replace. Post-panel installation enables better integration of the controller with the display HMI (Human Machine Interface), but the maintenance difficulty increases, and the system deployment is more difficult, requiring a higher level of engineering knowledge and program debugging time.


When the front panel is installed, the debugging time of the controller is very short, but the shortcoming is that the human-machine interface is very limited. Post-panel installation requires complex integration work, but successful design can significantly reduce costs, and you can better optimize machine operation through the HMI panel. Finally, work environment issues such as ambient temperature, humidity, and IP or NEMA ratings.


5, configuration and debugging


Since most users manually configure the controller, you need to look at the user interface and controller and consider whether they are convenient to use. Controllers for simple applications are usually set manually, but the more complex the customer needs, the more important the software is. Not only does the software improve configuration capabilities, but it also has a range of additional features, such as a trend/data logging view that gives you a clearer picture of system operation during debugging.


Depending on the complexity of the application requirements, more complex software can provide process simulation capabilities, enabling complex configuration testing in a simulated environment to prevent cost errors caused by setup errors. With these key issues in mind, you can be sure that the controller you choose is fully responsive and cost effective.