Torque and power measurement devices called dynamometers are used to determine the torque and power output of engines and rotating machines. There are three main types of dynamometers: absorption, driving, and transmission. Absorption dynamometers measure torque by absorbing mechanical energy using mechanisms like water brakes, hydraulics, rope brakes, or eddy currents. They consist of a rotor coupled to the engine under test that is braked to develop opposing torque. Torque is typically measured by mounting the dynamometer housing on trunnions and connecting it to a torque arm attached to weighing scales.

1. Torque and Power Measurement

2. Need?
• Applications for torque sensors include
determining the amount of power an
engine, motor, turbine, or other rotating
device generates or consumes
• Used in stress and deflection analysis
• Determining the performance
characteristics of machines
• Called dynamometers

3. classification
• Absorption type dynamometers: measures torque
by absorbing mechanical energy. Power generator
may be engine or motor
• Driving type: Dynamometer is power generator.
Like electric motor or generator. Used to measure
power required to drive unit.
• Transmission type: passive device. Neither
generates nor absorbs

4. Absorption type Dynamometers
• Water brake
• Hydraulic
• Rope brake
• Prony brake
• Eddy current

6. • A dynamometer consists of an absorption (or
absorber/driver) unit, and usually includes a
means for measuring torque and rotational speed.
An absorption unit consists of some type of rotor
in a housing. The rotor is coupled to the engine or
other equipment under test and is free to rotate at
whatever speed is required for the test. Some
means is provided to develop a braking torque
between dynamometer's rotor and housing. The
means for developing torque can be frictional,
hydraulic, electromagnetic etc. according to the
type of absorption/driver unit.

7. • One means for measuring torque is to mount the
dynamometer housing so that it is free to turn
except that it is restrained by a torque arm. The
housing can be made free to rotate by using
trunnions connected to each end of the housing to
support the dyno in pedestal mounted trunnion
bearings. The torque arm is connected to the dyno
housing and a weighing scales is positioned so that
it measures the force exerted by the dyno housing
in attempting to rotate. The torque is the force
indicated by the scales multiplied by the length of
the torque arm measured from the center of the
dynamometer.

10. Eddy current
• When a current carrying conducting material
moves through a magnetic field voltage is
generated, which results in current.
• If the conductor is a part of circuit then current
will flow through circuit. But if it is isolated than
voltage is still induced & local currents may flow
in a short circuited path within the bar itself. These
current are called eddy eddy currents, dissipated
in the form of heat.