INTRODUCTION

In this chapter, we are concerned with devices defined in international standard documents. Among these, the venturi meter is one of the oldest industrial methods of measuring flow, although other methods may be more common. Chapter 8 deals with other devices such as variable area meters, target meters, averaging pitot tubes, Dall meters, and other venturi, nozzle, and orifice-like devices.

As in the case of the orifice plate, the reader should have access to a copy of the latest version of the ISO standard (5167-1). I have refrained from repeating information that should be obtained from the standard, and include only the minimum information to provide an understanding of the discharge coefficients, the likely uncertainty of the various devices, and the type of material from which they may be constructed. However, although the amount of material published recently is not great, there is a growing interest in the use of some of these devices for difficult metering tasks and a reevaluation of their behavior, which may well lead to several reports in the next few years.