Module 2 : Sensors and signal processing

Lecture 4 : Velocity, motion, force and pressure sensors

  7.b Turbine meter

Figure 2.4.12 Schematic of turbine meter [1]

Turbine flow meter has an accuracy of ±0.3%. It has a multi blade rotor mounted centrally in the pipe along which the flow is to be measured. Figure 2.4.12 shows the typical arrangement of the rotor and a magnetic pick up coil. The fluid flow rotates the rotor. Accordingly the magnetic pick up coil counts the number of magnetic pulses generated due to the distortion of magnetic field by the rotor blades. The angular velocity is proportional to the number of pulses and fluid flow is proportional to angular velocity.

8. Fluid level

The level of liquid in a vessel or container can be measured,

  1. directly by monitoring the position of liquid surface
  2. indirectly by measuring some variable related to the height.

Direct measurements involve the use of floats however the indirect methods employ load cells. Potentiometers or LVDT sensors can be used along with the floats to measure the height of fluid column. Force sensed by the load cells is proportional to the height of fluid column.