Other Mechanical Primary Sensing Element
- Load Cells
- Torsion bar or Shafts
- Proof Rings
Cantilever:- A cantilever is shown in figure below, which is subjected to a force of its free end.
Where, F = Applied force, N;
L=Length of Cantilever, m;
E=modulas of elasticity, , N/m²;
I=Moment of Inertia,
b= Width of cantilever, m;
Load Cells:- Load cells utilize an elastic member as the primary transducer and strain gauge as secondary transducer as shown in figure below.
Torsion bar or Shaft :- These are primary sensing elements for torque. They are made use of in torque meters. The deflection or twist of the bar is proportional to the applied torque and the deformation is used as a measure of the torque.
Some torque meters are designed so that the angular displacement due to twisting of the bar is measured with the help of displacement transducer.
In other, the strain in surface of the bar which is proportional to the torque, is measured with the help of strain gauges.
Angle of twist,θ=16T/ΠGd³ radian;
T=Torque applied, Nm;
G=Shear modulus, N/m²;
d=Diameter of bar, m;
They are used for measurement of force, weight or load. The applied force causes a deflection which is measured with the help of electrical transducer. Prooving ring is a circular ring made up of steel as shown in figure below.
It may be subjected to either tensile or compressive forces across its diameter.
The common practice for measurement of displacement is attach a displacement transducer between the top and bottom of the proving rings. When the force is applied the relative displacement can be measured.