Overview

An instrument specification data sheet describes an instrument to a degree that leaves no doubt as to what will be supplied. The format of the instrument specification, also called a spec or data sheet, can change depending on the instrument type. This is because properly specifying a particular instrument depends on parameters that are specific to that type of instrument. Temperature, pressure, flow rate, specific gravity, and viscosity are process parameters that are often necessary to adequately specify an instrument. Other important information includes manufacturer, model number, materials of construction, face-to-face dimensions, process connections, power requirements, calibrated range, output, conduit connection size, area classification, enclosure type, mounting type, and set points.

An instrument spec sheet should be generated for every new instrument in a project. Usually, a generic data sheet is created for identical applications, given a unique number, and assigned to multiple instruments. For example, if ten identical pressure indicators with exactly the same process information are to be purchased, one data sheet could be generated with ten unique tag numbers for the indicators listed on it. This technique applies only to the most basic type of instrument, such as indicators or on/off valves. More complicated instruments that have many varying parameters cannot be easily combined. However, if multiple "trains" (identical process lines) are used in the design, generic instrument spec sheets are advisable for all instrument types.

A good design process generates a bi-directional flow of information. Since instrument tag numbers are listed on the...