Basics of the Linear Variable Differential Transformer (LVDT)

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⌚Timestamps:
00:00 - Intro
01:38 - Applications
02:00 - Structure
02:59 - Working
04:19 - Connection
04:39 - Module
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Linear Variable Differential Transformer or LVDT is a long, and somewhat intimidating name for a device that can also simply be described as a linear displacement sensor.
- Devices that include both electrical and mechanical processes are called electromechanical devices.
- Passive devices are not capable of generating energy; they can, however, store and also dissipate energy.
- Inductive refers to energy storage as an electromagnetic field.
- An electronic device that is capable of converting energy between one form into another is called a transducer.
Therefore, from its definition, an LVDT is an electromechanical passive inductive transducer.
It is an electronic device that has both electrical and mechanical processes, it requires an external power source to be able to operate, it stores electromagnetic energy and converts some form of energy into a readable signal… to describe the movement of a body along a sole axis, or what we call linear displacement!
An LVDT Sensor is one of the most accurate and reliable methods for determining linear distances. They can be used to detect vibration, for stress testing, to measure great displacements such as actuator movement, brake pedal travel.
- The LVDT consists of three high-density glass-filled coils, wound around a hollow, insulated tube that is non-magnetic.
- The primary coil is located in the center, and the other two are identical secondary windings, located at an equal distance of the primary coil.
- The differential part of this sensor’s name comes from the fact that those two secondary coils are in opposite phases.
They are electrically 180 degrees out of phase with each other and are connected in series. This connection results in an output that is the difference between the voltages in these two windings.
We can also see a cylindrical-shaped soft iron core that is ferromagnetic, meaning that it is highly susceptible to magnetization. This core is attached to a push rod that slides along the tube. This rod is attached to the body to measure its position displacement.
Continuous alternating current is applied to the primary coil, generating what we call primary excitation and a varying magnetic field. This primary excitation interacts with the secondary coils, which then induces current and voltage to be produced in the secondary coils.
- When the ferrous core is dead centered, which is also called at the null position, the induced magnetic flux to each of the secondary coils is equal. They are electrically 180 degrees out of phase with each other, therefore, they will cancel each other, and the output voltage will be zero.
This characteristic is used when calibrating an LVDT sensor.
As the core moves from this null position, the net induced voltage changes.
- When it moves upwards, the induced magnetic flux on the upper secondary winding is greater than the induced magnetic flux on the lower secondary winding. This results in a positive output voltage.
- When it moves downwards, the induced magnetic flux on the upper secondary winding is less than the induced magnetic flux on the lower secondary winding. This results in a negative output voltage.
Due to those characteristics, the direction in which the body is moving, and the distance can be determined by observing the voltage output increasing or decreasing, and its negative or positive value.
LVDTs can have lead wires or be provided with connection sockets. As both secondary coils are typically wired in series, the sensor has four wires or four connections in its connection socket. However, some LVDTs will provide the secondary coil lead pairs separately.
Today’s technology allows for signal conditioning in a way that prepares it for the next processing phase to be done inside the sensor’s housing.
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#RealPars #LVDT #Transformer

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Very informative video-thanks!

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Something that I didn't know about....Very nice and excellent presentation

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[@danielbartolome8807]

Great explanation thanks for sharing this video

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Well explained.

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Thanks for sharing.

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very helpfull thank you

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Our pleasure, Mehdi!

[@kalpanarajput6580]

Great information

[@realpars]

Glad it was helpful!

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speechless always awesome video 🔥🔥🔥

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Thank you so much!

[@divyan4271]

It was really nice explanation , could you pls share other instruments working process.

[@realpars]

Thanks for your comment and suggestion, Divya! Will happily pass it on to our course developers. Happy learning!

[@antonarasanastasopoulos3482]

I just learn all the sensors including lvdt in college...thats some nice videos ...next video will be strain gauge sensor right?😉😉hope you doing well mate thats a good work there... always better when you see those in action than a big pile of paper.nice one⚡⚡

[@monzurhasan3583]

Share your experience or upload Video

[@sivanesan4479]

Thank you for this video. please put the video about Beckhoff plc.

[@realpars]

Thanks for your suggestion, Siva! I will happily pass this on to our course developers. Happy learning!

[@sivanesan4479]

Tq sir and Tq for your reply about my message

[@balamurugan4993]

Team, kindly discuss about liner scale like potentiometric and magnetortive types

[@realpars]

Thanks for your topic suggestion, Bala! I will happily go ahead and pass this on to our course developers.

[@coldfinger459sub0]

When you said “no passive device can produce energy”. The first component immediately popped into my mind was a thermal couple. Here you have a passive device as the ambient temperature increases it starts producing energy.

[@johnjones5354]

First, it's thermocouple, second, it produces an EMF proportional to the difference of temperature at the thermocouple junction and the reference junction.

[@coldfinger459sub0]

@@johnjones5354 = voltage = current = power

[@realpars]

A passive sensor is one that has no external power source. While it is true that a thermocouple produces a voltage between the measurement and reference junction, there is no current flow until you put the thermocouple into a measurement circuit. Even then, the current is very small. You can configure a set of thermocouples to produce significant current, but in that case, you have a thermopile, not a thermocouple.

[@realpars]

@@coldfinger459sub0 A car battery, not connected, has a voltage across the terminals with no current flow (no complete circuit). Your analogy is correct when a load is applied across the terminals.

[@powerplantengineer6919]

Please make a video on MAGNETOSTRICTIV LINEAR TRANSDUCER.

[@realpars]

Hi Mukesh! Thanks for your message and your suggestion. I will pass this on to our course developers! Thanks for sharing and happy learning!

[@sivanesan4479]

Hi sir, I am working in Singapore what do I? for join your class without online

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Hi Siva, Thanks for reaching out! Great to hear your motivation to start your PLC programming training! RealPars is a 100% online learning platform, which you can join from everywhere on the globe. You can register via the following link learn.realpars.com/ Learning online can have great advantages. Besides that, as a subscriber, you obtain full access to our Technical Team who will answer any questions you might have along your learning journey! If you have any questions or concerns, always feel free to reach out to us over at [e-mail], and we're happy to help!

[@bitebonumbere1426]

Please RealPars how is the LVDT different from a potentiometer-type device? Nice video.

[@adisharr]

Look up how a POT works and then imagine the moving part of the transducer connected to the wiper of a POT.

[@bitebonumbere1426]

@@adisharr Many thanks.

[@realpars]

In a potentiometer, when the wiper moves, the resistance changes in the circuit. In an LVDT the voltage applied varies the magnetic field between the coils, thereby causing the push rod to extend or retract.

[@moaisl.3357]

Magnetorestriction is pretty robust and largely used in hydraulic applications, with high presision. I work with a combination of the 2. Lvdt in valve spool positionning (part on motion control system). While temposonic rods (magnetorestriction) is used for tool positionning.

[@realpars]

Thanks for adding that, Moaïs!

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