Force, Force measuring instrument, Scale and Balance, beam scale balance, pendulum scale, spring scale, Proving rings, Load cells, Hydraulic load cell, strain gauge load cell, Torque, Gravity balance method, Mechanical torsion meter, optical torsion meter, electrical torsion meter, strain gauge torsion meter, shaft power, dynamometer, absorption dynamometer, transmission dynamometer, driving dynamometer, prony brake dynamometer, rope brake dynamometer

1. Force,
Torque &
Power
Measurement
PREPARED BY :
RATNADEEPSINH JADEJA

2. Force
Force is defined as any cause that
produces, stops or change the
motion of a body or tends to
produce these effects.

3. Scale and Balances
 Balancing the force against a known gravitational force on a standard mass.
 A weighing machine, commercially known as scales is used for the measurement
of force and torque by comparison of weights. It is based on the principle of
equilibrium, produced by two torques as a result of forces acting at equal or
different distances from the fulcrum.

4. Beam Scale
The beam scale is used for
spring-testing devices
because its accuracy permits
testing a wide range of
springs with high accuracy.

5. Pendulum scales
The use of pendulum scales
requires that the force should
be steady for 2 to 3 seconds
for scale to come to rest.

6. Spring scales
The ordinary springs are
capable for giving results
accurately within the
accuracy of 0.5 to 1.0 %

7. Proving Rings
 Applying the force to some elastic member and then measuring the
resulting deflection.
 The proving rings are steel rings which are used as force standards. They are
particularly useful for calibration of material testing machines in situation where
dead weight standards are impracticable to use on account of their physical bulk.
 The rings are very stable and accurate to ± 0.1 % but deflection is not linear the
actual force is determined by reference to a calibration curve.

8. Proving
Rings

9. Load Cells
 Translating the force to a fluid pressure and then measuring the resulting
pressure.
 Load cells are elastic devices that can be used for measurement of force through
indirect methods.
 Load cells utilize an elastic member as the primary transducer and strain gauges
as secondary transducers. When the combination of the strain gauge – elastic
member is used for weighing, it is called a “load cell”

10. Hydraulic load cell
 These cells have been used to measure loads up to 25 MN, with an accuracy of
0.1% of full scale, resolution is about 0.02 %.

11. Strain gauge load cell
These cells converts weight or force into electrical outputs
which are provided by the strain gauges: these output can be
converted into various measuring instruments for indicating,
recording and controlling the weight or force.

12. Torque
 Torque is a measure of the force that can cause an object to rotate about an axis.
Just as force is what causes an object to accelerate in linear kinematics, torque is
what causes an object to acquire angular acceleration.
 Torque may be measured by the following methods:
1. Gravity balance method
2. Mechanical torsion meter
3. Optical torsion meter
4. Electrical torsion meter
5. Strain gauge torsion meter

13. Gravity Balance Method
Unknown Torque,
T = F × r

14. Mechanical Torsion Meter
In mechanical torsion meter the
angular deflection of a parallel
length of shaft is used to measure
torque

15. Electrical Torsion Meter

16. Strain gauge Torsion Meter

17. Shaft Power
 Shaft Power is the mechanical power transmitted from one rotating element
of a vehicle, ship and all types of machinery to another. It is usually calculated
as a sum of the torque and the speed of the rotation of the shaft.
 A dynamometer is a device used to measure the torque being exerted along a
rotating shaft so as to determine the shaft power input or output of power
generating, transmitting and absorbing machinery.

18. Dynamometers
 The dynamometers are classified as follows:
1. Absorption Dynamometers: The work on the principle that the power
measured is converted into heat by friction or by other means. The power
absorbed is lost as heat.
2. Transmission Dynamometers: they work on the principle that the power being
transmitted either to or from the dynamometer is not absorbed or dissipated.
After measurement, the energy is converted in a useful mechanical or electrical
form.
3. Driving dynamometers: These instruments measures power and also supply
energy to operate the tested devices.

19. Prony Brake Dynamometer
𝐵𝑟𝑎𝑘𝑒 𝑃𝑜𝑤𝑒𝑟 =
2Π𝑁𝑇
60
𝑤𝑎𝑡𝑡𝑠

20. Rope Brake
Dynamometer
𝐵𝑟𝑎𝑘𝑒 𝑃𝑜𝑤𝑒𝑟 =
W − 𝑠 Π 𝐷 + 𝑑 𝑁
60 × 1000
𝑘𝑊