LVDT Servo-amplifier help
LVDT Servo-amplifier help
(OP)
Dear All!
I am currently working on my very first project and i am having some problems. Any suggestion and help will be much appreciated.
In my project, i am trying to sense the position of a spool from LVDT sensor. In my circuit for LVDT, i am using a pic to generate a square wave. But as my LVDT operates on AC signal, therefore i am using a square to sinewave converter to convert my waveform into sinewave.That signal is passing through LVDT and goes to a precision rectifier to convert my sinewave back to dc signal. But i am having following problems:-
a) I am getting 60 to 80mV noise on the output. How can i get rid of it.
b) Is it possible to generate a sinewave directly from the pic? If so any help please.
c) Is there any suggestion to improve my precision rectifier (demodulator) and square to sinewave generator.
Please accept thanx in advance for all ur support.
Regards.
I am currently working on my very first project and i am having some problems. Any suggestion and help will be much appreciated.
In my project, i am trying to sense the position of a spool from LVDT sensor. In my circuit for LVDT, i am using a pic to generate a square wave. But as my LVDT operates on AC signal, therefore i am using a square to sinewave converter to convert my waveform into sinewave.That signal is passing through LVDT and goes to a precision rectifier to convert my sinewave back to dc signal. But i am having following problems:-
a) I am getting 60 to 80mV noise on the output. How can i get rid of it.
b) Is it possible to generate a sinewave directly from the pic? If so any help please.
c) Is there any suggestion to improve my precision rectifier (demodulator) and square to sinewave generator.
Please accept thanx in advance for all ur support.
Regards.





RE: LVDT Servo-amplifier help
The LVDT output has phase information. Use that by having a phase-sensitive detector rectify your signal. That will take out most of the noise. Low pass filtering will take out the rest. Control the detector switches with control signals from the PIC - essentially the same square wave that you feed to the sine converter. You may even try to feed the square wave directly to the transducer. It has been done before.
Lots of information on the net. Google LVDT and "phase sensitive detector". The "quadrature" phenomenon is very real in these circuits. Google that too.
Gunnar Englund
www.gke.org
RE: LVDT Servo-amplifier help
What positional accuracy are you trying to achieve from the LVDT? 0.1% is certainly achievable using a fairly basic detector circuit built using precision components. A clean sinusoidal excitation signal will almost certainly reduce the need for a more sophisticated detector capable of dealing with the non-sinusoidal secondary waveform. I guess it depends on where you want to expend your effort.
Skogs,
Most of my LVDT experience is on long travel types ranging from 3" or so up to 3' or so. The majority are Schaevitz designs. Are the small ones much more difficult to deal with in terms of the electronics?
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Sometimes I only open my mouth to swap feet...
RE: LVDT Servo-amplifier help
Using a square wave and a simple synchronous detector made from a 4066 or a couple of FETs was really the easiest way of doing it.
Gunnar Englund
www.gke.org
RE: LVDT Servo-amplifier help
skogsgurra!!
I understand ur point. So do u mean to say that i will have to use a phase sensitive detector between my LVDT output and precision rectifier (demodulator)?. If so will i have to provide an AC signal to phase sensitive detector as well from the same source which is providing input signal to LVDT? If so, then why? i mean this is my first encounter with phase sensitive detectors. Could u please explain its operation a bit? How will it help in decreasing the sound level.
Thanks
a lot
RE: LVDT Servo-amplifier help
Have a look at http:
Gunnar Englund
www.gke.org
RE: LVDT Servo-amplifier help
RE: LVDT Servo-amplifier help
RE: LVDT Servo-amplifier help
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Sometimes I only open my mouth to swap feet...
RE: LVDT Servo-amplifier help
Gunnar Englund
www.gke.org
RE: LVDT Servo-amplifier help
RE: LVDT Servo-amplifier help
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Sometimes I only open my mouth to swap feet...
RE: LVDT Servo-amplifier help
RE: LVDT Servo-amplifier help
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Sometimes I only open my mouth to swap feet...
RE: LVDT Servo-amplifier help