Looking for circuit that can detect a nearby tuned circuit...

[Graham &/or Annie Law]

Hi
Help please...

I need a circuit that can detect a nearby tuned circuit...

The object with the tuned circuit embedded within it is made to look like a
rock

The 'rock' is dropped into a detection coil which will pick up the resonant
frequency to identify the type of 'rock'

There will be three types of rock each with it's own resonant frequency.

I am an electronics engineer but I have little experience with RF.

I need a relatively simple circuit that can give me three logical outputs
one for each rock type.

This is for an educational facility and I am not commercially involved.

Any help much appreciated.

 

[John Miller]

I need a circuit that can detect a nearby tuned circuit...

The object with the tuned circuit embedded within it is made to look like a
rock

The 'rock' is dropped into a detection coil which will pick up the resonant
frequency to identify the type of 'rock'

There will be three types of rock each with it's own resonant frequency.

I am an electronics engineer but I have little experience with RF.

I need a relatively simple circuit that can give me three logical outputs
one for each rock type.

Something like that used in the Schlage/Westinghous access card system
should be just the ticket.

 

[PeteS]

You can use a single oscillator, if you have the time to characterise
the circuit.

Make your rocks around 3 different masses of an inductive material.
When you drop each rock through the 'detection coil' (which should be
part of the tank on your oscillator), they will perturb the output
frequency and amplitude, but each will perturb it differently.

For best detection, integrate the output of the oscillator and watch
the signal amplitude (now as a DC signal).

This is the basis of certain electronic coin scanners.

Cheers

PeteS

 

[CWatters]

Hi
Help please...

I need a circuit that can detect a nearby tuned circuit...

Investigate those security labels they stick on expensive good in some
stores. They are tuned circuits that are detected when they go through the
checkout.

 

[CWatters]

Investigate those security labels they stick on expensive good in some
stores. They are tuned circuits that are detected when they go through the
checkout.

More..

http://www.miyake-inc.com/security-label.html

http://www.theftcontrol.com/securitylabels.htm