Level measurement and verification - Introduction

Nothing seems more trivial than level measurement! Alongside temperature, pressure and flow measurements, it's one of the four basic functions performed by industrial instrumentation. However, the multiplicity of methods employed demonstrates that level is, in reality, a more complicated parameter to master than it first appears. The complexity of level measurement is inherent in the concepts involved. Whether it's the different measurands (level, true head, manometric head), the specific features of the stored product (tranquilization of liquids, particularities of bulk solids), the criticality of the application (measurement chain, reliability, safety) or its adaptation to environmental conditions (extreme temperatures, external aggressions), a multitude of parameters need to be taken into account in order to optimize the measurement process. In addition to these purely technical considerations, level measurement can also be used in commercial transactions when purchasing a quantity (volume or mass) of stored product. In this case, legal metrology rules and standards add further constraints that need to be taken into account. The implementation of a level measurement system must respond to a variety of safety, profitability and product quality issues. Level measurement is ubiquitous in industry, and is used in a wide range of applications, from control (automation management, process engineering) to threshold detection (triggering alarms), not forgetting the recording of measurement campaigns for system monitoring and analysis (water tables, dams, rivers, reservoirs, water or fuel consumption, etc.). The industrial sectors most concerned by these applications are the chemical and petrochemical industries, the agri-food and pharmaceutical industries, the water treatment sector and industries linked to energy and raw materials.