Course - HND in Engineering


  • Q1. Three common types of electromagnetic transducers and three types of actuators
  • Principle of Operation
  • 1) Electromagnetic Flow meter
  • 2) Linear Variable Differential Transformer
  • 3) MEMS Accelerometer
  • B. Actuators
  • 1) Linear Solenoid
  • 2) Pneumatic Actuators
  • 3) Hydraulic Actuators
  • Q2. Three common types of electromagnetic transducers and three
  • 1) Transducer: Magnetic inductive flow meter
  • 2) Thermocouples
  • 3) Pressure transducers
  • Q3.
  • Reference

Unit 21 Electric Machines

Question 1. Analyse three common types of electromagnetic transducers and three types of actuators for any of the stated areas provided in the scenario

Solution: Three common types of electromagnetic transducers and three types of actuators

Transducer is an electronic device that converts one form of energy into another form of energy. Transducer belongs to two categories such as input transducer (sensor) as well as output transducer (actuator). Input transducer or sensors receives a form of physical energy as well as converts that energy into signals that can be read. For example, microphone that converts physical sound waves into electrical signals. Pressure transducer is an another example that converts physical pressure into reading that canone can be understood by anyone.Transducer is a device that provides usable output in response for specific input (Siddique,2015).

The quantity that need to be measured in the system like temperature, pressure, flow, displacement are given as input. The transducer will provide the equivalent output for the input. Transducer have a vital role in the engineering instrumentation systems.
Electromagnetic transducer (EMT) is Inductive type of transducer in which relative motion of mechanical device is converted to the voltage signal using the magnetic field property.

Principle of Operation
Coil is wound on the static core and is connected to the output terminal. The mechanical plate of ferromagnetic material is changed the position with respect to the magnet and the flux is produced in the magnetic field and as results there is voltage induced in the coil that is wound over the permanent core.These types of transducers are non-contact method.

Electromagnetic transducers are active transducers. Some examples of electromagnetic transducers are as follows:

It is converting electromagnetic waves into electric current as well as vice versa

Light bulb
It converts the electrical power into the visible light

1) Electromagnetic Flow meter

Electromagnetic Flow meters are used in the utility for measurement of fluid flow in the pipes. This is based on the Faraday`s Law of Electromagnetic Induction. In this Magnetic field is generated and made across the liquid flowing in the pipe. As per the Faraday`s law of conductive liquid, the magnetic field will be induced and creates voltage signals which will be picked by the electrodes placed over the pipe walls. As the flow is more the voltage induced will be more which is directly proportional to the law and the voltage signal will be used to find the flow movement (Jiasheng, 2020)

Transducer are a device the perform conversion one quantity to another proportional electrical quantity (eg. volt or current).Electrical Conductivity is for electricity to flow (μS/cm) so higher the this value the flow meter is best suited

Flow can be calculated E=k*B*D*V, where V is velocity of the liquid flow
D is distance between the electrodes
B is magnetic flux
E is induced voltage
• Less accurate due to magnets
• Sometime electrodes get corruption
• Not suited for low conductivity (deionised water
• Not able to detect gas/liquid
• cross section of pipe is required
• Best suited for sanitary purpose
• Pressure drop is not observed
• High reliability
Industrial applications
They do not have protrusions over the pipe they are well suited for more applications. Highly used in pulp, paper industries, metal and wastewater treatment chemical and petrochemical.

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2) Linear Variable Differential Transformer

LVDT is based on inductive transducer, which converts the linear motion to electrical signals (voltage/current). Differential voltage is observed across the secondary side of the transformer. The movement range from little to higher values measured using the LVDT (Siddique¸2015).
• It is designed using the transformer with primary winding (P) and secondary windings (S1) and S2) over the cylindrical core.
• Secondary windings has equal turns (n).
• Primary winding in the transformer is connected to AC voltage that creates magnetic flux in the air gap and thus voltages are induced in the S1 and S2
• Dynamic iron core is used for displacement measures and this has high permeability and has high sensitivity
• Housing of the LVDT is in steel and has full shielding over electromagnetic and electrostatic

Principle of operation

Primary side is energised with AC voltage and due to the magnetics core the secondary side voltage is induced at e1 and e2. The output for this connection will be eout= e1-e2.
As we move the core in both the direction,the signal output will be linear to the actual motion in the core.

• No contact between coil and core (No frictional loss)
• Long life in operation
• Less power consumption
• High accuracy
• Easy to connect and modify
• Low Hysteresis
• Highly prone to stray magnetic field
• Impacted by temperature and vibrations

There are used in aerospace, automotive and medical industry for more precise and getting accurate results.
• Widely used in Metrology for process industry
• Power station to monitor the hydraulic cylinder
• Digital spring push and pneumatic probes
• Turbine blades
• vacuum displacement probes
• Block gauges

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3) MEMS Accelerometer

MEMS (Micro electro Mechanical Systems) is the advanced technology in the instrumentation area with the help of micro electronic devices. These uses the devices like cantilevers and membranes to construct the devices and have used high-level microfabrication process for developing the devices (Yu ,2020)
They are in small and can be integrated with multiple devices to get a full functionality.
MEMS Accelerometer is used to measure the acceleration, force that were subjected on the devices. Current piezoelectric devices are huge is size and have difficult in installation.
With these MEMS, they are easy to fixed to the devices and able to detect the multi axis positions.
This is capacitive type and value vary based on the capacitance between the two plates.
There are 2 plates in placed parallel have distance between them as 'd'. E is permittivity.
Co = Eo * E A/d = E A/d
EA = E0 * EA
Where A is Electrodes Area
as we get values for E, A and d, the capacitance

MEMS Accelerometer transducer has movable plates or microstructure that will be connected to the external devise where we need to measure the motion or movements.

Movable plates and outer plates form the capacitor plates. When acceleration is a placed, the microstructure will displace the plates and create the variance in the capacitance and with that, we can measure voltage for the displacement.

• High sensitivity and high accuracy
• Low temperature sensitivity
• Low noise
• Low Impedance has a fixed value
• More prone to EMI

• Optical MEMS used in optical fibre in telecommunication
• RF MEMS in Antennas, Relay microphone
• Widely used in Automotive and Aero sensor devices
• In digital Camera for stabilization

B. Actuators
Electromagnetic Actuators are based on the electromagnetic mechanical principles which transform the one energy to another energy.

1) Linear Solenoid
Solenoids are the widely used as Electromagnetic actuator. This converts the electrical energy to linear motion are called Linear Solenoid. This converts the electrical energy to a force or to motion (Akubude, 2020).
The structure is that coil is wound over the cylindrical core of ferromagnetic materials/plunger (extend and contract).

Principle of Operation
As the DC turned ON over the coils, it creates a magnetic field and plunger will move as per the flux in the coil and will compress the spring based on the force and speed of the movement that depends on the flux.
When the DC turned OFF, the coil will get DE energised and will reduce the flux and will restore to the initial position and that leaves the spring.

With the duty cycle of Solenoid, the ON/OFF duration of the coil is controlled using the MOSFET other electronic circuit.

2 way solenoid valves, 3 way solenoid valves

• Less power consumption
• Installation is easy
• Work for AC and DC supply
• It is highly sensitive to voltages
• Coil life time is less
• Valve will be not closed if the adequate magnetic flux not available
• conveyor belts
• relay applications
• lock mechanisms

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2) Pneumatic Actuators

Pneumatic Valve actuators operates based on gas or air. The pressure created will be used to control the valve opening and closing as it operates over piston (Li¸2020)

There are two major components in this type

Pilot: This senses the pressure (high or low) of the valve and send a electrical signal to the actuator to open or close.
Control Value: this is placed below the actuator and operates as the pneumatic signal (4-20 mA) and process for open/close.
Position of the valve is fully controlled by the air pressure. By varying the air pressure the spring pushes the diaphragm towards or upwards. By increasing the air, pressure causes the spring to push the diaphragm to control valve, closes fully, and reverse the operation as the air pressure is reduced.

• Highly used for temperature for -20- 300F
• It safe and fully provides good environment
• Light weight
• less maintenance
• Less efficient due to high pressure loss
• not scalable for other application
• Limited conditions due to compressed air
• Mostly used in Power plant generation
• Air powered actuators for linear or rotary
• Linear air cylinders
• Servo pneumatic actuators for position the cylinders

3) Hydraulic Actuators

Hydraulic Actuators uses the hydraulic pressure to activate the control signals. It depends on Pascal's Law with pressure applied over the area will produce the force. Will use the low compressibility and prevent from leakage (Padole¸2020).

The motion obtained can be linear or rotary. The cylinder has tube inside and air pressure applied to one part of the piston. Piston will move in one direction and in return the spring helps restore to rest position. Various type of actuators are hydraulic helical valve, wellhead protection

• Mainly used for high pressure applications
• operates at 4500psi
• Hold constant torque and forces
• Able to install components with distance
• Prone to leak of fluid and less efficiency
• Mostly used in opening and closing of door or lids
• Clamping and welding
• Cylinder

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Question 2. Three common types of electromagnetic transducers and three

Based on the given use case the we could

1) Transducer: Magnetic inductive flow meter
Transducer type: Electromagnetic principle
Inline magnetic flow meter
With accuracy of +/-0.9%
Connectivity: Bluetooth or IO link for IIoT operations
Electrical conductivity: minimum 20 µS/cm
Power supply: 18-36vDC
Current consumption:<300mA
Digital output: 4-20mA
Back (emf)=B*L* v
Where B- Flux density (tesla)
L : length of the rod (meters)
V= flow of the

These are affected by the corrosion and hence it shall be protected using the cathodic protection on the metallic surface. Galvanic protection shall be used. Performance of the transducer is impacted by EMI (Electromagnetic interference). There shall be an isolation transformer provided. The EMF protection is provided by grounding plates to the shunt path of the Cathodic protection. Proper isolation is provided between flanges. With Galvanic anode system and impressed current anode are used for better operations.

2) Thermocouples
These are used for measuring temperatures from ptc100 or J and K sensors.
Type of Transducers: Temperature transducers (Passive)
Temperature range: -451F to 2400F
Material used:Nickel Chromium
EMF over the temperature L -8.0 to 60 mV
Seeback coefficient: 50.21(µV/°C)
RTD is used only for low temperature range and less fragile for installation
Due to long wiring in the sensor, the EMI and RF can affect the signal. The Thermocouple output will be in mV and may be sometimes will be distorted.Using the proper transmitter with IEC 61326 standard compliance will have less these problems (Siddique¸2015)

3) Pressure transducers
Pressure transducer is used to measure the boiler pressure.
Special purpose to with stand the shock and vibration immunity.
Isolation and breeds are provided to over the EMI and
Accuracy of 0.2% over the full-scale output.
Output has standard with 10,000psi and calibration is also done.
Electrical excitation would be 9-36vDC regulated
Output signal: 4-20mA

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Question 3. Analyse the practical application of any two transducer and actuator that can be used in the IIT initiative embarked by your company in activity 2 and to make recommendations to improve the operating efficiency


Temperature sensor used in the power plant are highly need to be interconnected with IoT system. Therefore, we could easily get the data from the sensor to the monitoring system. Using the transmitter with wireless and have an option to output to the 4-20mA and comply with HART will be highly recommended.

These will help for not having extended wires and that would cause an EMI/EMC issues with those wires.Maintenance will be easy and able to get the diagnostics data from these sensor and able to use to use the scalable sensor. This will also increase the accuracy of the sensor. Reduce the control system cost and reduce the ground loops (Bonaldi,2020)

Thermal mass flow meters
• Vortex shedding flow meters measure the saturated and super heated steam.
• The flow of water and gas can be measured and we can get high accuracy with less leakage and low maintenance cost.
• Flow meters with no movements will have high operating life.
• Measuring the right blend of gas and other gas for applications
• Stream flow, compressed air and natural gas and burner control

All these shall have the digital output and Bluetooth connection and IO link for the data transfer from the devices.

Linear actuator used in linear valve actuators where the high temperature stem valve need to be operated.Piston Actuators are used to closing the value in some heat exchangers.

Hydraulic value Actuators need to be connected internet with IO link or MEMS Actuators are used for some applications. Drill rigs, offshore plants, excavators. These will be used with gas transmission for above 20ft above the floor level.

Need to have high precision control valve with good accuracy and with fail-safe spring during the power OFF conditions.

Able to detect have valve leakage and used in steam cycle and trigger alarms with some electronic parts.


  • Q: What are electromagnetic transducers and actuators?
  • Q: Three common types of electromagnetic actuators and their applications, design, and operation?
  • Q: Can you suggest two possible transducer and actuator combinations for a generic IIT initiative?
  • Q: How to analyze the operating efficiency of these combinations?
  • Q: Recommendations for improving operating efficiency?

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