Rotational speed, also known as revolutions per minute (RPM), measures the number of full rotations made by an object within one minute. It is calculated by dividing the number of rotations by time. Instruments like tachometers are used to measure rotational speed in various applications such as measuring engine speed in vehicles or flow rate in medical devices. There are different types of tachometers including mechanical, electronic, digital, and those that use contact or non-contact methods to measure speed. Rotational speed sensors are also used to measure speed in applications like wheel speed sensors in vehicles. Viscometers use rotational viscometry techniques to measure viscosity by rotating a spindle in a fluid and measuring its rotational speed.

1. Rotational speed
measurements
PRESENTED BY: SAIF MOHAMED HELMY AMIEN

2. Rotational speed
Rotational speed (also known as speed of revolution or rate of rotation), of an object rotating
around an axis is the number of turns of the object divided by time,
specified as:
1) revolutions per minute (rpm),
2) cycles per second (cps),
3) radians per second (rad/s),

3. The speed at which an object rotates or revolves is called rotational speed. Unlike linear speed, it is
defined by how many rotations an object makes in a period of time. The formula for rotational speed
is Rotational speed = rotations / time but linear speed = distance / time.
The rotational speed of the engine must always match the frequency of the grid for the power-
generating station in all respects. Hence, the speed of the engine shall be calculated as follows:
n=60f/p
where
n=Rotational speed, rpm
f=Frequency of the grid, Hz
p=Number of pair of poles

4. Speed measuring instruments
• Speed measuring instruments are vary with the job whether measuring traveling speed , wind
speed, acceleration or engine speed, there is a proper instruments for calculating that from of
speed.
Police use Radar & lidar To measure traffic speed .
Cars have speedometer For travel speed and Tachometer for engine speed. Accelerometer also
used With cars speed measurements. Meteorologist Used anemometer and radar to create their
whether forecasts.

5. Tachometer
The tachometer is a measuring instrument that is used to measure the operating speed of an
engine in revolutions per minute. It is also known as a revolution counter.
The device can measure the rotational speed of the shaft or disc when the machine is in
motion. It also indicates the angular speed of a rotating shaft.
This instrument is usually used to estimate traffic speed and volume/flow. It is used in cars,
aircraft or other vehicles. It shows the rate of rotation of engine crankshaft along with the
marking that displays the safe range of rotational speed.

6. Working Principle of Tachometer:
An Electric Tachometer works on the principle of relative motion between the magnetic field
and shaft of the coupled device. The motor of tachometer works as a generator,
i.e. it produces the voltage based on the velocity of the shaft. It counts the number of rotations
the crankshaft is making per minute.
It is essential for the user to know the RPM of the engine and its operating range to avoid
unnecessary damages. The device works on either an alternating or direct current.

7. Types Contact type of Tachometer:
This type of tachometer is usually fixed to the machine or electric motor. It works by bringing a
freely spinning wheel in contact with a rotating shaft or disc.
The shaft drives the wheel to generate the pulses. These pulses are then read by a tachometer
and measured in revolution per minute. It can also calculate the linear speed and distance.

8. Electronic tachometer
It is made up of electronic components used to measure the engine speed. It measures the
speed in revolution per minute.
It is mainly used in the dashboard of the car to measure the driving speed.
It uses a magnetic pickup placed near a rotating engine to generate electric pulses. These pulses
have frequency proportional to the engine speed.

9. Digital tachometer
It is a digital device that measures the speed of the rotating object. It is an optical encoder that
identifies the angular velocity of a rotating shaft or motor.
It is commonly used in automobiles, airplanes, medical and instrumentation applications.
Time measuring tachometer:
It calculates the speed by measuring the time interval between incoming pulses. It is more
suitable for measuring low speed with high accuracy.

10. Frequency measuring tachometer
It calculates the speed by measuring the frequency of the pulses.
The revolution of the device depends on the rotating shaft and is suitable for measuring the high
speed.
The modern version comes with a sophisticated digital circuit to perform the count, storage,
calculation, display and reset to deliver output in rpm.

11. Mechanical tachometer
It has a centrifugal force on a rotating mass to stretch or compress a mechanical spring.
It uses a series of consecutively tuned reeds to identify engine speed.
It displays the engine speed by indicating the vibration frequency of the machine.
Function
It captures sample and then AVG it after taking couple of internal reading from rotating parts
There are primarily 2 types as per my knowledge--Mechanical type and IR sensing type

12. Application
It is used to measure rotational speed.
It can measure the flow of liquid with the help of an attached wheel with an inclined angle.
It is applicable for the medical sector to measure the blood flow rate of the patients.
It is used in vehicles to display the rate of engine crankshaft rotation

13. Speed Sensors - Wheel Speed Sensor (WSS)
Rotational speed (even at low vehicle speed) Air gap measurement Dependable functionality
with large air gaps (up to 4.5 mm between sensor and encoder) Standardized VDA data protocol
High resistance to extreme temperatures, from -40°C to +150°C
Operating Temperature: -40 to 302 F
Output: Voltage
Power Requirements: DC Powered

14. Viscometers
Thermo Scientific HAAKE High-range portable viscometer,
Small, battery-operated design for quick field tests and comparative measurements
Rotational viscometers provide quick, exact, and reliable measurements for a variety of fluid
types ranging from paints and shampoos to sauces and oils
Accuracy: 5 ±% Full Scale
Dynamic Viscosity Range: 30 to 400000 cps
Technology Type: Rotational Viscometry (Spindle)

15. Reference
Wang, L., Yan, Y., Hu, Y., & Qian, X. (2013). Rotational speed measurement through electrostatic sensing and correlation signal processing.
IEEE Transactions on Instrumentation and Measurement, 63(5), 1190-1199.
Pan, C., Chen, L., Chen, L., Jiang, H., Li, Z., & Wang, S. (2016). Research on motor rotational speed measurement in
regenerative braking system of electric vehicle. Mechanical Systems and Signal Processing, 66, 829-839.
Pan, C., Chen, L., Chen, L., Jiang, H., Li, Z., & Wang, S. (2016). Research on motor rotational speed measurement in
regenerative braking system of electric vehicle. Mechanical Systems and Signal Processing, 66, 829-839.
Urbanek, J., Barszcz, T., & Antoni, J. (2013). A two-step procedure for estimation of instantaneous rotational speed with large
fluctuations. Mechanical Systems and Signal Processing, 38(1), 96-102.
Baszynski, M., & Pirog, S. (2013). A novel speed measurement method for a high-speed BLDC motor based on the signals
from the rotor position sensor. IEEE Transactions on Industrial Informatics, 10(1), 84-91.
Zimroz, R., Urbanek, J., Barszcz, T., Bartelmus, W., Millioz, F., & Martin, N. (2011). Measurement of instantaneous shaft speed
by advanced vibration signal processing-application to wind turbine gearbox. MTA Review/Military Technical Academy
Review, 18(4), 701-712.
Angrisani, G., Roselli, C., & Sasso, M. (2013). Effect of rotational speed on the performances of a desiccant wheel. Applied
Energy, 104, 268-275.