On the DCS point counting method
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Are there any criteria or methods for counting the points in a DCS? The number of instruments has already been counted; how can the number of points be determined? For example, a mixing motor would have AI current, DI remote/local signals, DI operation status, DI fault signals, and DO start/stop control – so are we counting five monitoring points in total? What are the rules or basis for this? Also, for control valves, is it necessary to take into account a given signal AO as well as a feedback signal AI? Do isolation valves have DI and DO signals? Is it related to the object it’s linked to?
The signals available on a device depend on which signals you need to monitor. For example, in the case of an inverter, depending on the requirements, one AI may be sufficient to handle frequency feedback; or another AI can be added, such as one for current feedback. This varies depending on actual requirements, cost control, and design conventions, among other factors. By the way, I’d also like to ask everyone: how is the so-called point balance calculated? Is it \"remaining points/total points\" or \"remaining points/used points\"?
Redundancy is probably around 30% of the actual number of points; for high-risk processes, SIS systems seem to follow a 1:1 ratio
DCs generally come with an export function, allowing direct export; or one can ask the manufacturer’s engineers to handle the export – some manufacturers provide specialized software for use in supervision tasks
It is recommended to leave 15%~20% margin for each module, with the remaining channels in the module allocated as spare points
For example, if a module has a capacity of 8 points and 6 points are used, is the remaining amount 33.3% or 25%?
For example, if a module has a capacity of 8 points and 6 points are used, is the remaining amount 33.3% or 25%? Redundancy is not calculated in this way; a control system often consists of hundreds or even thousands of modules, and it is necessary to calculate the redundancy based on the total number of modules in order to obtain a relatively accurate redundancy level of 15%~20%.
Of course I know that. For example, if I have only 8 points and use 6 of them, how do I calculate it?
Using 6 as the base, with 2 backups for 6, the redundancy is 33.3%.
The point count for DCS should be calculated separately for different types of input and output signals