LVDT circuit - need to explain how it works

[Johnbob]

If any one could help me or point me in the right direction that would be awesome... Thank you!!

 

[davenn]

welcome to EP

specifically,
what do you want to know ?
where did you get the circuit from ?
is this something you are actually building ?
what instructions came with the circuits ?



Dave

 

[Johnbob]

welcome to EP

specifically,
what do you want to know ?
where did you get the circuit from ?
is this something you are actually building ?
what instructions came with the circuits ?

OTHER THAN MOD's, NO ONE ELSE ANSWER TILL MY QUESTIONS HAVE BEEN ANSWERED BY THE OP

Dave

what do you want to know ? Just how the basic sub parts of the circuit work
where did you get the circuit from ? I'm an apprentice and have been given a task to build a circuit to measure the linear displacement of a LVDT, this is the circuit i have been given to explain how it works and to build.
is this something you are actually building ? Yes
what instructions came with the circuits ? none.

 

[davenn]

what instructions came with the circuits ? none.

well its a well drawn/laid out circuit, rather than a hand drawn one so there must be more information about it available
so some one gave you this circuit and said build it ??
did you ask them for the background info ?

what is your knowledge of Op-Amps like ?
Have you done any study on Op-amps or look at any tutorials online ?
there are masses of them available ....

on the forums we really like to try and help people learn ... learn to work through circuits, learn to research for info, etc

If we just spoonfeed you the answers, you will never learn anything

This is why I'm asking all the questions


Dave

 

[Johnbob]

well its a well drawn/laid out circuit, rather than a hand drawn one so there must be more information about it available
so some one gave you this circuit and said build it ??
did you ask them for the background info ?

what is your knowledge of Op-Amps like ?
Have you done any study on Op-amps or look at any tutorials online ?
there are masses of them available ....

on the forums we really like to try and help people learn ... learn to work through circuits, learn to research for info, etc

If we just spoonfeed you the answers, you will never learn anything

This is why I'm asking all the questions


Dave

well its a well drawn/laid out circuit, rather than a hand drawn one so there must be more information about it available
so some one gave you this circuit and said build it ?? Well yeah pretty much, we get given a circuit, told to research the circuit, we then have to explain how the circuit works to a mentor so we can move on to build and test.
did you ask them for the background info ? nope

what is your knowledge of Op-Amps like ? Pretty shocking tbh, I know a few configurations. I know that the three op-amps in a row on the part 2 of the circuit diagram are configured as intergrators with the first one being bias stabalised by a large resistor. The second part of the part 2 circuit; the op amp is working as a differential amplifier with the transistors working as a push pull amp. As for the 1st part of the circuit all i know is that the two first op amps are working as half wave rectifiers producing a pulsating DC... That is my basic knowledge of the circuit, I'm just looking for something a bit more comprehensive and for clarification really.
Have you done any study on Op-amps or look at any tutorials online ? Not much knowledge on op amps other than the very basics.
there are masses of them available ....

 

[davenn]

Thanks for answering

We so often get people asking really vague questions on the forums and we need to get more background info
on both the person's electronics knowledge as well as that it is they are trying to do

In the mean time you may want to have a look at some of this guy's tutorials, even I have learnt lots over the years
http://www.bing.com/videos/search?q=op-amp+video+tutorials&qpvt=Op-Amp+video+tutorials&FORM=VDRE

I will let others to respond now.

 

[Johnbob]

Thanks for answering

We so often get people asking really vague questions on the forums and we need to get more background info
on both the person's electronics knowledge as well as that it is they are trying to do

In the mean time you may want to have a look at some of this guy's tutorials, even I have learnt lots over the years
http://www.bing.com/videos/search?q=op-amp video tutorials&qpvt=Op-Amp video tutorials&FORM=VDRE

I will let others to respond now.

okey dokey, cheers bruh

 

[Arouse1973]

Have a look at state variable oscillators.
Adam

 

[hevans1944]

In Circuit Diagram Part 1 the two rectifier circuits are actually full-wave rectifiers. Consider the circuit that uses IC4C: for both positive and negative signals from the LVDT secondaries, the signal is applied through a 20 kΩ "summing" resistor to the inverting input of IC4B, which has a 100 kΩ feedback resistor. The gain for this path is -5 for both positive and negative signals. For positive signals only, IC4C inverts these with a gain of unity and applies the inverted (negative) signal through a 10 kΩ summing resistor to IC4B for a gain of +10 to the output of IC4B for this path. Thus a 1 V positive output from the LVDT secondary will result in (+10 -5) or +5 V output from IC4B. A 1 V negative output from the LVDT will result in a (0 +5) or +5 V output from IC4B because the rectifiers do not pass this signal through to the 10 kΩ "summing" resistor and the negative LVDT output is inverted to a positive output from IC4B. Clever, huh? But you could have figured that out.

The secondaries of the LVDT are generating opposing voltages which cancel when the core is coupling equal energy from the primary to both secondaries. This is the null position. On either side of null, one secondary will produce more voltage than the other and the full-wave rectified difference appears at the output of IC4B, later smoothed by the two RC filters before being amplified by IC4C.

Note the polarity of the diodes is reversed between the two rectifier circuits. Is this important? Can you explain why?

 

[LvW]

Have a look at state variable oscillators.
Adam

Yes - good recommendation. As an alternative, you could search for "Integrator-oscillator" .