Control loop

To aid unique identification of equipment, each loop and its elements are identified by a "tagging" system and each element has a unique tag identification.

Based on the standards ANSI/ISA S5.1 and ISO 14617-6, the identifications consist of up to 5 letters.

The first identification letter is for the measured value, the second is a modifier, 3rd indicates passive/readout function, 4th - active/output function, and the 5th is the function modifier. This is followed by loop number, which is unique to that loop.

For instance FIC045 means it is the Flow Indicating Controller in control loop 045. This is also known as the "tag" identifier of the field device, which is normally given to the location and function of the instrument. The same loop may have FT045 - which is the flow transmitter in the same loop.

Letter	Column 1 Measured value	Column 2 Modifier	Column 3 Readout/passive function	Column 4 Output/active function	Column 5 Function modifier
A	Analysis		Alarm
B	Burner, combustion		User choice	User choice	User choice
C	User's choice - usually conductivity			Control	Close
D	User's choice - usually density	Difference			Deviation
E	Voltage		Sensor
F	Flow rate	Ratio
G	User's choice (usually gaging/gauging)	Gas	Glass/gauge/viewing
H	Hand				High
I	Current		Indicate
J	Power	Scan