Instrumentation and DCS instruments installed in the control room
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As shown in Figure 1, the first option indicates that the instruments are installed in the control room, meaning that the instrument panels are placed there; the second option implies that the instrument panels are also installed in the control room while the signals are displayed on the DCS. So why not use Figure 2 instead, where the instruments on-site are directly connected to the DCS for display? Why have two sets of instruments that can both display information in the same control room, thereby requiring an additional instrument panel?
The first diagram shows instruments installed on-site without remote transmission, while the second shows DCS remote display and control instruments.
Take a look at HG/T 20505-2014 \"Functional Indicators and Graphic Symbols for Process Measurement and Control Instruments\"
On the second floor, it’s incorrect: a horizontal line inside the circle indicates instruments in the control room, while the absence of such a line indicates instruments on-site. Why use two types? For example, in the control room where there is an instrument display controller for flammable and toxic gas detection alarms, a circle with a horizontal line in the middle is used; if there is no display controller and the system connects directly to the DCS, then a box, circle, and horizontal line are used
Add a horizontal line in the middle to indicate that only display is available, along with control functions; wouldn’t that be a DCS? And what if there’s no horizontal line in the middle but instead a box?
Why can’t I see the image? It remains the same even after trying to update it