• C type bourdon tube is made up of an elliptically flattened tube bent in such a way as to produce the C shape as shown in the fig. The free end of this tube is closed or sealed and the other end (fixed end) is opened for the pressure to enter.
• The free end is connected to the pointer with the help of geared sector and pinion. Calibrated scale and pointer is provided to indicate the pressure.
• The pressure which is to be measured is applied to the bourdon tube through open end. When this pressure enters the tube, the tube tends to straighten out proportional to applied pressure.
• This causes the movement of the free end and the displacement of this end is given to the pointer through mechanical linkage i.e. geared sector and pinion.
• The pointer moves on the calibrated scale in terms of pressure. The relationship between the displacement of the free end and the applied pressure is nonlinear.