1. Force, Torque, and Shaft Power MeasurementBy
Aj. Somchai Triratanajaru M.Eng KMUTT,
B.Eng KMITL
Term 1/2554

2. LECTURE OUTLINE 1. Standards and Calibration
2. Basic Methods of Force Measurement
3. Characteristics of Elastic Force Transducers
4. Resolution of Vector Forces
5. Torque Measurement on Rotating Shafts
6. Shaft Power Measurement (Dynamometers)
7. Gyroscopic Force and Torque Measurement
8. Vibrating-Wire Force Transducers
*Major part of this presentation are from Measurement Systems, Ernest O. Doebelin

3. 1.Standards and calibration
Force, (F=ma); thus a standards for force depends on standards of mass and acceleration.
Mass standards-> cylinder of platinum-iridium
called International Kilogram.
Acceleration -> drive from standards of length
and time.
g -> sea level and 45o latitude cm/s2
If not , must be compensated.

4. Force standards

5. 2. Basic methods of force measurement
There are seven methods introduce in the
reference text book. Some methods are only
use in lab. We will focus on weighting and
torque measuring instrument But keep in mind
that it is still have so many methods out there.
Use this information as the guide line for further
study.

6. 2.1 Balancing it against the known gravitational force on a standard mass, either directly or through a system of levers.

7. 2.2 Measuring the acceleration of a body of known mass to which unknown force is applied.

13. 2.3 Balancing it against a magnetic force developed by interaction of a current-carrying coil and a magnet.

14. 2.4 Transducing the force to a fluid pressure and then measuring the pressure.

15. 2.5 Applying the force to some elastic member and measuring the resulting deflection.

16. Strain-Gauge Load Cell

17. Strain-Gauge Beam Transducers

25. Young's modulus
Young's modulus, E, can be calculated by dividing the tensile stress by the tensile strain:
where
E is the Young's modulus (modulus of elasticity)
F is the force applied to the object;
A0 is the original cross-sectional area through which the force is applied;
ΔL is the amount by which the length of the object changes;
L0 is the original length of the object.

26. Young's modulus..
Young's modulus is the ratio of stress, which has units of pressure, to strain, which is dimensionless; therefore Young's modulus itself has units of pressure.

27. Young's modulus… Material Modulus (GPa) Aluminum 69 Copper 117
Steel 207

28. LVDT Force Transducer

29. Piezoelectric Load Cells

30. Torque Measurement of Rotating Machines: Dynamometers

31. Schematic of Dynamometers

32. Chassis Dynamometer

34. Servo-controlled Dynamometer

38. Further reading and more exercises
Text.
Process control Instrumentation
technology
Curtis D. Johson