Solenoid Parameters

[Valtrex]

Hi,
I need to design a solenoid or some other magnetic coil so that I can pick-up vibtations from a metal plate. I know that the type of the metal, the size of the solenoid, the number of turns etc will affect performance but I don't know how. I would appreciate if anyone could direct me to any books or resource that would be a guide. Thanks in advance.

 

[nbucska]

Material, amplitude and freqency range ? accuracy req'd? <nbucska@pcperipherals.com>

 

[automatic2]

Try something real simple first, like glueing on a speaker diaphram to your metal. High frequencies would likely require a pizo device, while lower frequencies could use a mag/coil combination. You can purchase detectors from several of the larger instrument suppliers if your doing an engineering type function.

 

[47gandalf]

Rather than design your own solenoid, why not look at LVDT (linear variable differential transformer) approaches? You would buy the LVDT from a vendor and couple its movable core to the unit whose vibration you want to sense. When the core moves with respect to the solenoid winding an output signal is created that is proportional to the movement.

An interface circuit is easier these days because some IC vendors make chips to handle all the details of interfacing to the transducer itself.

Then feed the output signal of the electronics circuit to your destination. They are very sound mechanically and quite sensitive. Not sure what your spec requirements are in this area.

 

[Valtrex]

Thanks for your insightful suggestions. Does anyone have any suggestions for assembling an LVDT to measure the vibrations of the metal without touching it. The vibratons range between 0 to 5 kHz. the ampltiude shoulod be in the order of 1/10 of a millimeter. Thanks again.

 

[OperaHouse]

So what are you really trying to measure? An absolute displacement, a relative magnitude, or frequeny? If you are measuring something lightweight, adding a transducer's mass can greatly change what is happening. Integrated photo emitter/receivers that are ast at an angle can be used for non contact displacemet measurments. I would buy a cheap accelerometer. Epoxying on a ceramic transducer is another option. Getting down to zero is a real problem and just how would you calibrate this system.

While on this subject, They now make thumper transducers for those cars that like to shatter windows. These bolt onto seats, perhaps for hemeroid relief. At around $30 a pair, they can make a pretty cheap shaker table.