This manual will show how to measure flow in tubes with throat devices. The environment can be everything from industrial plants to laboratories. The performance of the flow measurement can be as good as 0.7 % uncertainty of actual flow from 10 to 100% flow if - Design - Manufacturing - Installation in tube - Instrumentation - Calculation of the flow is done according to the Matematica approach. The Matematica approach gives You full control over every parameter that have an impact on Your flow measurement. Over 20 parameters, like physical properties of the fluid, pipe roughness, installation in tube, differential pressure transmitter performance has to be under Your control, or the flow measurement will malfunction. It cannot perform better then the weakest part. The Matematica approach is described here , step by step, and every step is calculated and described by the computer software Processline from Matematica. The calculations are based on scientific documentation, like the standard ISO 5167-1 from 1991, amendment 1 from 1998 and german VDI/VDE journals 2040 and 2041, it means very good credibility. The flow must be a one phase flow, it means the fluid can be a gas (-mixture) or a liquid (-mixture), but not a gas-liquid mixture. I will also show how to improve old installations of throat-devices. This is done by identification and reduction of the biggest error-sources and, if needed, improvement of the square root flow calculation by a new algorithm called the Matematica algorithm. This algorithm is a correction of the square root function, and can reduce the flow-calculation error for gases from sometimes 10% to 0%. This algorithm can be keyed into any modern computer as a function-block.
