Pressure gauge with bellow is the pressure gauge that is equipped with bellow. Bellow is thin metal which is shaped like an accordion bellow. Same as pressure gauge bourdon tubes, bellow also expands when the inside pressure is greater than outside pressure.
Any changes in inside pressure of bellow will produce mechanical motion backward or forward. Movement of backward and forward through tuns and twister tube then to be converted into the form of circular movement of pointer on scale numbers that have been calibrated as shown in Figure 1 below.