Through over the real world the RPM sensor is very essential instrument. Example as, Rotating machinery need speed sensing for functional systems including control, monitoring, and safety. Turbine engine rotor speeds must be monitored closely to maintain safe operation. A motor driver need to monitor the car speed for safe driving, this car speed is taken from rpm sensor.
What is RPM Sensor?
The device which is used to measure the rotational speed of any rotating shaft, disk or any rotating objects is called RPM sensor. RPM stands for Revolution Per Minute.
The rotation speed of a shaft or disk, such as that of a motor or other machinery, is measured and indicated by an RPM meter, and it is shown as RPM on any HMI screen.
While the machine is in operation, the speed measurement is taken by the instrument known rpm sensor. It is also commonly known to by other names, like an RPM gauge and a rev-counter.
It may operate on an optical, electrical, or electromagnetic basis.
RPM Sensor Working principle.
The RPM sensor working principle can be electromagnetic, electronic, or optical-based. That means the basic working principle depends on types of RPM sensors. Different types of RPM sensor work in deferent way.
Inductive sensor for RMP measurement: Inductive speed sensors utilize electromagnetic induction to determine the speed of a spinning object. They are typically made up of a coil and a magnetic core that produce voltage when a metallic target on a rotating object passes near the sensor.
An inductive sensor is a device whose operation depends on a changing magnetic field in an inductive coil. When a metal object enters into the field of action, it is captured and recognized. It uses a unique generator that creates a certain amplitude of oscillation. When an object made of metallic or ferromagnetic material reaches the unit's field of action, its oscillations change, indicating the existence of the object.
Hall effect sensor for RPM measurement: Hall-effect rpm sensors work on the Hall effect principle, which states that the presence of a magnetic field causes a voltage to be developed in a conductor. These sensors usually use a magnet placed on the rotating object and a Hall-effect sensor to measure the speed. Unlike inductive sensors, a Hall Effect sensor's output signal does not vary by the rate of change of the magnetic field. The outcome voltage is typically in the mV range and is amplified by integrated electronics circuit located inside the sensor enclosure. The final output voltage signal is typically in digital waveform pulses (square form). Each tooth that comes into contact with the sensor surface causes one waveform pulse. The amplitude of the output signal waveform remains constant; but the frequency changes correspondingly with rpm. So, by counting the wave pulse it is easily possible calculate the rpm.
Advantages of Hall Effect Sensor
- As it has non-contact sensing which provides greater durability.
- Durable and dependable in adverse circumstances, resistant to dust, moisture, and vibration.
- Designed for a broad range of speeds, including near-zero velocity.
- Variations in the magnetic field may have an impact on accuracy.
- Sensing distance is limited in comparison to other sensor types.
- Additional components may be required for signal conditioning.
Optical sensor for RPM measurement: Optical rpm sensors use light to measure the speed of a spinning object. They usually have an infrared LED and a photodiode to measure the amount of light reflected or interrupted by the revolving object. According to the way of sensing speed this device can be two types: transmissive type and reflective type.
Reflective type- The photo sensor detects whether the light transmitted by the LED is reflected by the revolving wheel or not.
Advantages of Optical Speed Sensor
- Non-contact sensing minimizes wear and tear, hence increasing longevity.
- Excellent precision and accuracy, especially in clean environments.
- Dust, wetness, and vibration have a minimal impact.
- Sensitivity to variations in ambient light can affect the sensor's performance.
- In general, the cost is higher than for other types of sensors.
- It requires more complicated circuitry which can lead to increased design complexity.
Study more: Vibration Sensor Working Principle and Applications.
RPM Sensor Types.
Digital- These rpm meters contain electrical circuitry, a processor, a sensor, and an LCD or LED display. Such instruments can carry out statistical calculations. Digital tachometers are becoming more popular, and instead of dials and needles, they provide numerical readings on a display.
Analog- These RPM meters furnish a needle-and-dial interface. These devices do not have the ability to save measurements or calculate information such as average deviation. The speed turns into to voltage using an external frequency-to-voltage converter. As a result, this voltage is displayed on an analog voltmeter marked with the RMP scale.
Contact and Non-Contact RPM Meters- The contact type requires physical contact with the rotating shaft. on the other hand Non-contact rpm meters, which are highly efficient, convenient, and accurate, make no touch with the rotating shaft.
Time and Frequency Measuring Tachometers- The time-based digital tachometer determines the equipment's rotational speed by measuring the time interval between incoming pulses. The frequency measurement instrument calculates speed by measuring the frequency of incoming pulses. It is more accurate for high-speed measurements, and the rotation of this tachometer is determined by the revolving shaft.
