Bourdon tube uses a coiled tube which as it expands due to pressure increase causes a rotation of an arm connected to the tube
- The left side of the face, used for measuring manifold vacuum,is calibrated in centimetres of mercury on its inner scale and inches of mercury on its outer scale.
- The right portion of the face is used to measure fuel pump pressure and is calibrated infractions of 1kgf /cm²on its inner scale and pounds per square inch on its outer scale
- A: Receiver block. This joins the inlet pipe to the fixed end of the Bourdon tube (1) and secures the chassis plate (B). The two holes receive screws that secure the case.
- B: Chassis Plate. The face card is attached to this. It contains bearing holes for the axles.
- C: Secondary Chassis Plate. It supports the outer ends of the axles.
- D: Posts to join and space the two chassis plates.
1.Stationary end of Bourdon tube. This communicates with the inlet pipe through the receiver block.
2.Moving end of Bourdon tube. This end is sealed.
3.Pivot and pivot pin
4.Link joining pivot pin to lever (5) with pins to allow joint rotation.
5.Lever. This an extension of the sector gear (7).
6.Sector gear axle pin.
8.Indicator needle axle. This has a spur gear that engages the sector gear (7) and extends through the face to drive the indicator needle. Due to the short distance between the lever arm link boss and the pivot pin and the difference between the effective radius of the sector gear and that of the spur gear, any motion of the Bourdon tube is greatly amplified.A small motion of the tube results in a large motion of the indicator needle.
Advantages of Bourdon Gauges
3.Good accuracy except at low pressure.
Disadvantages of Bourdon Gauges.
1.Susceptible to shock and vibration
2.Gauges are subjected to hysteresis