How could you physically setup an lvdt to work? it is too small!!?

Question

i understand how an lvdt works...however i saw one at work,,,,but it fits on the palm of my hand,... now from what i understand the object that you want to measure its displacement is connected to the iron core that moves between the two secondary coils..how can you physically hook them up if the transformer is so small.... i am confused..thanks

Answer 1

I use LVDTs every day.  The small ones are for small displacement, and the large ones for large- obviously.  The core that goes in and out of the center of the LVDT body causes a shift in the coupling of the magnetic field.  This shift is a modulated bi-phase AC signal.  The primary is "hooked up" to a driver circuit (each LVDT has designed operating frequency) and the secondary is wired to give a bi-phase output giving both direction and displacement.  Smallness has no meaning.  Look at a single transistor on the microprocessor that is inside your desk computer or laptop.  the output is simply amplified and detected.  Usually you have a synchronous sample-and-hold signal to return the output to base-band.

I might be confused by your question, due to a Congress and President that have betrayed our country for their own gain, but that's another story...

Answer 2

usually they have a rod attached to the core sticking out of it. Just bolt it on. The details are your job!  

Without more info, what more can I say?

Wikipedia:

The linear variable differential transformer (LVDT) is a type of electrical transformer used for measuring linear displacement. The transformer has three solenoidal coils placed end-to-end around a tube. The centre coil is the primary, and the two outer coils are the secondaries. A cylindrical ferromagnetic core, attached to the object whose position is to be measured, slides along the axis of the tube.

An alternating current is driven through the primary, causing a voltage to be induced in each secondary proportional to its mutual inductance with the primary. The frequency is usually in the range 1 to 10 kHz.

As the core moves, these mutual inductances change, causing the voltages induced in the secondaries to change. The coils are connected in reverse series, so that the output voltage is the difference (hence "differential") between the two secondary voltages. When the core is in its central position, equidistant between the two secondaries, equal but opposite voltages are induced in these two coils, so the output voltage is zero.

When the core is displaced in one direction, the voltage in one coil increases as the other decreases, causing the output voltage to increase from zero to a maximum. This voltage is in phase with the primary voltage. When the core moves in the other direction, the output voltage also increases from zero to a maximum, but its phase is opposite to that of the primary. The magnitude of the output voltage is proportional to the distance moved by the core (up to its limit of travel), which is why the device is described as "linear". The phase of the voltage indicates the direction of the displacement.

Because the sliding core does not touch the inside of the tube, it can move without friction, making the LVDT a highly reliable device. The absence of any sliding or rotating contacts allows the LVDT to be completely sealed against the environment.

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