Do the circles in the diagram mean output inversion?
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Do the circles in the image mean inversion? Well, if it seems illogical like this and hard to understand, then…
The circles in the diagram represent the inversion of the output of a logic gate, that is, the result obtained by inverting the input signal. This notation is used to simplify the drawing of logic diagrams and to help readers understand the functionality of the circuit. For example, if the input to a logic gate is 0, then the output is 1 ； If the input is 1, the output is 0. Such a logical relationship can be represented by a circle. If you are not familiar with this way of representation, you might find it difficult to understand. However, once you become familiar with this notation, reading logic diagrams will become much easier. .
Whose DCS logic diagram is this? Generally speaking, logically, a dot means inversion.
This should be a startup interlock protection condition for a device.
If it’s an inversion, is the logic correct?
Looking at the diagram, the circle indicates that the input signal is inverted; it is the circle on the right output terminal that indicates inversion of the output. I also checked the logic and didn’t find any issues. The function should be to ensure that the commands to open the three valves and the commands to close the three valves are mutually exclusive, as a condition for automatic startup.
My understanding is that this is done to ensure the interlock conditions necessary for starting the fan later on; the equipment can only be started when the inlet valve, outlet valve, and discharge valve are all fully open. By inverting the signals indicating whether a valve is fully open or closed, it is possible to prevent the equipment from being enabled for operation if the valves are not fully open. As can be seen from the \"AND\" logic, all of these conditions must be met before automatic startup is permitted.
Full open is 0, full closed is 1; the circle after full closed indicates inversion. It follows an AND logic, meaning that either a full open state or a state that is not full closed will trigger the subsequent result, and either condition will suffice to trigger it.
The logic is sound: a signal indicating opening means the valve has indeed been opened, while a signal indicating closing is its inverse, indicating that the valve has left the closed position. These two conditions are combined using “AND” for safety reasons – both conditions must be met to prevent any accidental operation.