Following letter I
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Dear experts: Is the letter I that follows the instrument tag number used only to indicate functions in a DCS? What is the function of a transmitter? For example, is a pressure transmitter with a display specified using PIT- as the designation?
The subsequent letter I indicates the indication function, without distinguishing whether it is in the control room, at the site, in the DCS, or in the field chamber. In other words, indicating functions can all appear in these situations. Transmitters with a small gauge usually do not rely on this gauge to indicate the status; if it is important to emphasize that the transmitter has a gauge for indication, it is labeled as PIT.
How are the displays in the circuit indicated, such as those next to the tank?
Is it an indicator next to the tank that shows the liquid level on-site? A circle without a solid line in the middle can be used (a circle without a solid line indicates that the installation or implementation of this function takes place on-site); PI or PG is indicated at the top, while the instrument tag number is indicated at the bottom. Use PI to emphasize instructions, and use PG to emphasize on-site observation.