While there are some cases where deadband is helpful, in most applications the effect is extremely detrimental and confusing. Deadband can arise from any sources either intentionally or inadvertently. Deadband creates deadtime and for certain conditions excessive and persistent oscillations.
Deadtime is the easiest dynamic parameter to identify and the one that holds the key to better control. Deadtime found visually or by a simple method can tell you what is limiting the ability of the loop and what the remedy is. In most loops, you as the automation engineer...
In some applications, throttling of the manipulated flows is difficult or impossible. In the biochemical industry, where precise (good resolution and sensitivity) throttling valves without any crevices (to meet sanitary requirements) are rather limited (there are exceptions such as the Fisher Baumann 83000-89000 series).
Today’s smart digital valve positioners have incredible capability and flexibility as to tuning, performance and diagnostics. Here we look at how to get the most out of these positioners by tuning and by making sure the valve assembly does not hinder performance and gives the position feedback needed.
Here are key relatively straightforward principles and practices not commonly known that can make a world of difference in the performance of feedforward and ratio control systems. Also, guidance is offered for the setup and automatic identification of the parameters needed by the use of software designed to tune PID...
Why do many process control technologies fail to make prime time being relegated to special applications that are few and far between? Here I give what I see as the keys to a technology being successful and widely used in plant applications.
If the total loop deadtime becomes larger than the open loop time constant, you have a deadtime dominant loop. There is a lot of misunderstanding posed by this difficult challenge including a lot of prevalent myths. Here we look at how we get into this situation, what to expect and...
Here we finish up the extensive presentation of how to get the most out of your PID. We start with a look at the contribution of each mode and show how to estimate performance metrics from tuning settings and how excessive integral action and insufficient proportional action create oscillations.
The major types of process responses and the different worlds of process applications are presented. Additionally, the oversight of not including and understanding the contribution of automation dynamics is addressed. The discussion of the response of the PID is started.
The key aspects of good vessel temperature and pH control are often not recognized. Here we provide some simple guidance and overview of the benefits of a particular strategy and implementation guidelines that should be commonly used.
