This code is a general guide to the principles and methods used for calibrating and checking process analysers. It covers initial calibration in the factory or on the plant, analyser validation (¡.e. in-service checking) and routine calibration including the use of control charts.

It is impracticable to produce a specific calibration procedure applicable to a wide variety of analysers. This code therefore describes in general terms the various alternative and often compiementarytechniques available, and discusses their background, merits and limitations.

The content and presentation recognizes that the effort available for calibration is limited. The methods recommended therefore, require only reasonable expenditure of effort. In some cases this leads inevitably to procedures which, though adequate, may be less rigorous than could be evolved on purely technical and theoretical grounds. Also, the Code of Practice is intended for people directly involved with supplying, using and maintaining analysers, and these people are generally not specialists in quality measurement principles and techniques or conversant with statistics. Therefore, as far as possible, the Code of Practice avoids the explicit use of statistical methods and uses instead descriptions and explanations more familiar in conventional instrument work. Particular technical terms are defined in the text as necessary.

Throughout this document the word 'analyser' denotes a process analyser, also variously described by users as stream analyser, on-line or in-line analyser, product quality monitor, etc. The code is not intended to cover automatic or semi-automatic instruments used mainly in laboratories to analyse discrete samples, though some of the principles and techniques described may apply to such instruments.