ABSTRACT
This chapter aims to discuss the science of instrument-building for experimentation in fluid flows. The pressure measuring devices meant for measurements in fluid flow may broadly be grouped into manometers and pressure transducers. Various types of liquid manometers are employed depending upon the range of pressures to be measured and the degree of precision required. When large pressures of the order of mega pascals have to be measured, the liquid column required for such pressures becomes extremely large and measurement with manometers becomes unmanageable. Static pressure measurements are very sensitive to the inclination of the tube to the flow direction. For instance, in measurement of wind speed with a pitot-static probe the probe axis has to be aligned in line with the local flow direction, within a few degrees to achieve the required accuracy in the measurement. Low-pressure gauges are usually referred to as vacuum gauges. Measurement of low-pressures requires considerable care on the part of the experimentalist.
