Sensors are the instrumentation that measure the system outputs and provide information to the system controllers. Examples would be temperature probes, pressure gauges, and flow meters. Even a scale at your home is a sensor!

Process Controls – Have Any Feedback?
What are Process Controls?
We’ve learned about computers and programs in past volumes, and we benefit from computers daily, from our email to creating presentations, and more. Beyond our everyday use, how do we use these at AbbVie? Many of our manufacturing sites use computers and programs to manage our processes via process controls, but what exactly are process controls? Check out below to learn more!
Process Controls In a Nutshell
Process controls are a combination of control theory and control systems that monitor, control, and optimize and industrial production processes.
In general, think of it as having an Input that creates a specific output. If the output isn’t the desired result, then the process controls come into play to control/modify the process and input to ensure the desired output is achieved.
For manufacturing, process controls can be summed up in 3 steps:
- Establishing a setpoint (desired output)
- Measure the current Process Variable (output) [A] of the system
- Control system [B] uses that process variable to modify the input [+] to the system and then repeat until steady state is reached (when process values no longer change).

Control Theory 101
Control theory combines engineering and applied mathematics to develop the overarching algorithm that controls system inputs to generate the desired outputs.
One of the most common control schemes is a feedback loop. In a feedback loop, the output (process variable) is used to adjust the system inputs to reach the desired setpoint. This is the example shown in the above box.
Feedback loops are iterative where the system makes numerous adjustments to reach the target setpoint. The graph below illustrates this. The orange line is the system output and the blue line is the setpoint. Over time, the two lines meet and the output equals the setpoint.
Control Systems 101
A control system is the physical set of sensors and controllers that manipulate a system for process controls.


Controllers are the computers that manipulate inputs in the system to reach the desired output based on data from sensors. For example, a controller will open a flow valve more when more flow is needed through the system.
Control Systems at AbbVie
A single control loop may be used to control one variable of a process, but if you have hundreds of variables, managing all of those at the same time becomes increasingly difficult. One of the most common control systems to do this is a distributed control system (DCS). DCS consists of an overall view of all control loops in a system, along with supervisory control over them. Additionally, they provide an entire overview of the state of the system—an HMI can pull info from the DCS for plant operators use to interact with the process equipment and process itself.

Heating/Cooling Systems
Heating and cooling is used everywhere at AbbVie. A DCS could control a heating/cooling system by measuring a temperature (process variable) the then adjusting the flow of coolant (input) via a flow control valve (controller). This has use from our production vessels all the way to our A/C systems!
Vision Systems
Within assembly and packaging operations, vision systems are used to measure aspects of the process and properly accept or reject parts off the line. This is a great example of how a sensor can be used by a DCS for advancing a recipe, versus just adjusting variables to maintain a production process. Both aspects are critical to successful production!

Production Recipes
Many of our plants use what is called a recipe, the overall production process step-by-step, to create our products. This recipe is programmed and controlled by a DCS to ensure the process is executed correctly and each step in order, every time. Think of it like baking a cake, you wouldn’t put the baking pan in the oven first, and then your ingredients – the DCS ensures the right order happens!