Posts Tagged ‘Set Point’
Pulse is Okay, but Doublet is Better
The Pulse and Doublet tests both allow practitioners to observe the process moving in opposite directions, but which is better?
Read MoreHow to Perform a Step Test
Tuning PID controllers is a multi-step process. While it is important to understand each step in the process, performing the bump test and collecting dynamic data is the most crucial step that generally dictates the outcome. This post delves into one particular type of test – the Step Test – before introducing other tests commonly used in PID controller tuning.
Read MoreWhat Is a Set Point Filter?
Names – like looks – can be deceiving. While jumbo shrimp are big relative to other shrimp there’s very little about them that could be considered gargantuan. So there should be no surprise to learn that in the realm of process control a Set Point Filter has nothing to do with filtering noise within a control loop’s data.
Read MoreHow Can I Correct for Noise Using External Filters?
Choices, choices. In the realm of process control practitioners are regularly forced to choose between competing options. Consider a PID control loop: Should it be tuned for faster disturbance rejection or tighter Set Point tracking? Should the Derivative Term be used or does the PI configuration provide a sufficiently fast Settling Time? And the choices go on and on. In that sense there are multiple choices for filtering noise too – options that provide very different benefits. Fortunately when it comes to filtering for Signal Noise the choice is typically clear.
Read MoreHow Can I Correct for Noise Using Internal Filters?
Noise is inevitable. To one degree or another it’s evident in the data of most every production process. Sure it can be absent in academic settings and similar lab environments where simulations often generate sanitized data. However, in the real world of industrial manufacturing noise is a factor that cannot be avoided. Failing to account for or manage noise can be a recipe for – well – failure.
Read MoreHow Does the Derivative Term Affect PID Controller Performance?
Derivative is the third term within the PID. In mathematical terms the word derivative is defined as the slope of a curve. Seen in the context of strip chart data derivative represents the rate of change in error – the difference between the Process Variable (PV) and Set Point (SP). Like the proportional and integral terms within a PID controller, the derivative term seeks to correct for error. Valuable as the third term can be in maintaining effective control, experience suggests that appropriate uses of derivative are not entirely clear.
Read MoreHow Do I Detect Valve Issues and Prevent Failures?
It’s generally known that the behavior of final control elements (FCEs) (valves, air handlers, etc.) change over time. Like most things the dynamics of FCEs are different from the time they’re first installed to the time they’re serviced and ultimately replaced. Sometimes the change in dynamic behavior is subtle. Other times the change is dramatic. Unfortunately that’s the nature of things, and that’s the primary reason why monitoring for valve issues is beneficial.
Read MoreWhat is Variance? What Metrics are Useful in Identifying Process Change?
Ever walk onto the production floor and just sense that something was different? Whether it was something you saw, heard or even felt, a certain sixth sense kicked in and triggered an alert something’s changed. With what takes place at a production facility change is an everyday occurrence. Considering the typical facility’s size, the interconnected unit operations, the network of piping and instrumentation, and the nonstop throughput, there’s no avoiding change. In fact, a key part of the job is simply staying one step ahead of it.
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