Q.2 Differentiate between the piezometer and pressure gauge.
Piezometer – It is the simplest instrument, used for measuring, moderate pressures. It consists of a glass tube, one end of which is connected to the pipeline or vessel, in which pressure is to be measured, while other end is open to the atmosphere as shown in fig. 2.1. The height to which the liquid rises up in the tube, gives the pressure head directly. A piezometer tube cannot be used for measuring negative or vacuum pressures.
Pressure Gauge- Pressure gauges are mechanical gauges, which embody an elastic element, that deflects under the action of the applied pressure, and this movement when mechanically magnified, operates a pointer Fig. 2.2 Piezometer Tube moving against a graduated circumferential scale. These gauges are used for measuring high pressures and where very high precision is not required. They can be used for pressure measurement in boilers and pipes, where tube gauges are inconvenient to use.