Instrument index is a document containing list of instrument devices within a process or plant.


The instrument index will include the tag number of all physical objects (e.g. field instrument, visual alarm and indicator) and counterfeit tools commonly referred to as “soft markers” (e.g. DCS indicator, alarm, controller).

The instrument index will be built at the beginning of the project and considered as a live document that should be kept updated even if the plant was active.

The instrument index will be updated if a plant or system modification contributes to the addition, removal, or reset of the instrument

In the instrument reference text, the following information should be stated but not limited to:

  • Tag number
  • Loop Number
  • Type of Instrument
  • Location
  • Service description
  • P&ID Number
  • Line number or equipment number
  • I/O Type
  • Control System
  • Range or set point along with engineering unit used
  • Applicable reference Document (Instrument Data Sheet Number, Hook-up Drawing Number, Instrument Layout Number, Loop Drawing Number)
  • Package Number
  • Manufacturer
  • Model Number

The following guidelines are required in preparing the instrument index guide to complete the information: Reference diagram: P&ID, HMB

P & ID (Piercing and Metal Drawing)
From P & ID all tool tag number is collected with its associated details such as service description, instrument type, line / machine number, set point. A good quality P&D can have a distinctive feature that separates the control system to which each device is connected.

HMB (Temperature Balance and Object)
We can see the width of the metal scale based on the process data for each broadcast from HMB (Temperature and Balance Material).

Reference document: Cause and effect

The instrument index should include the number of tags related to fire and gas. Fire and gas devices usually do not appear in P&ID, they are said to have an effect and effect instead.

The purpose of the instrument index

From its descriptive name, the instrument index will be sent as a reference for many purposes as follows:

  1. As a basis for preparing an I / O list by simply removing the I / O tag number
  2. Searching, Listing, Sorting tag number

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