Implement Metal detector circuitry in LabVIEW

[F._Schubert]

You get the short because you only have the coil attached, I guess. Put in there some resistor as Lynn suggested.

Felix

[DPARK]

I wish I know more about all.... okay.

I recognized the advice with the resistor but my coil needs the inductance value of 6.3mH ... I hope to can keep his value with a resistor...

I just wanna buy a 100k resistor now and hopefully I can start then. But is my VI with the DAQ on the right way to create the signal with the "simulate signal"-block? I've never heard about FPGA... 

[DPARK]

Okay Felix,

the resistor (10 Ohm) is conected in series to my receiver coil. Now I get a very smal signal in the amplifier (but not a short signal).

Well, I need to create the sinusoidal signal through LB and the DAQ board to the Transmitter coil. You told me that my version with

the "simulate signal"-block doesn't work. How should I create the right signal now? I don't know how to do this otherwise.

Thank you!

Simon

[DPARK]

Hey,

Okay... Now I have an additional poit of view. The DAQ cannot produce the kind of current I need. It can supply up few mA probably. That's why I don't get the same signal with the help of a signal generator.

Is it possible to amplify my signal to increase the current?

Thank you!

Simon

[F._Schubert]

Hi, I was busy doing my own work so I didn't reply.

You are right that you need an amplifier to get the current. Ask around in your lab, you not really need any special.

Here is the link to an explanation how you can performe syncronized DAQ tasks:

http://zone.ni.com/devzone/cda/tut/p/id/3615

Felix

[Henrik_Volkers]

You already have a small amplifier: your soundcard output 😉

However as more power you put into the send coil as better will be your SNR and range.

BTW nice coils 🙂 but I miss the shielding (with gaps! Don't create closed loops with the shield!)

I would try the following:

Constantly sending a sharp strong pulse, repetition rate 90 - 1kHz (??).  Important: As much current as possible, and short (some 10 µs, we don't want to heat the sending coil 😉 )

(I would use a 555 and a power FET, you want more software so  a DO driving a FET  ) 

It's not important to do it in sync with the reading (might help, but I would trigger on the read coil) , and as long as the send pulse is not changing I wouldn't read it.

Now read some pulses from the receiving coil with your DAQ and do a FFT. Do this with different materials, with some luck you can determine the material by it's spectrum.

[DPARK]

Thank you Felix!

I'll try to amplify my signal. Hope there is equipment to do this...

But why do I need to performe synsronized DAQ tasks?

Best, Simon

[DPARK]

Hi Henrik,

I think you recognized that I am also from Germany. Thank you for advices.

To the coil shieldling:

I didn't forget the shielding with the gap. The aluminium tape shield is under the plastic wrap. I connected both shielding wires but I didn't use it because:

If I connect the shield with any GND from DAQ board, I don't get a signal... Do you know how to connect the shield?

To can follow you, I need many information from you: I've never heard from FET etc... (sorry) So, what's my next steps:

1. I want to amplify the current to my transmitter coil. Therefore I'll use a device from the lab.

2. Then I should build up a "power FET"!?! How can I do this and which components should I use?

3. After that I'll create a puls with LV via DAQ board

I definitely need your help with this stuff, there isn't so much time left. Thank you so much Henrik!

Best, Simon

[Henrik_Volkers]

If you don't mind  keep on posting in english 🙂

A FET is a field effect transistor . You can use such a component as a switch to turn on the current to your coil controlled by a anlog or digital output of your device. However switching coils leads to high voltages 😉

Since you asked that question.... How is your practical electrical background?

As amplifier: Any old sound amplifier should do that job. Replace the speaker with the coil. If your coil resistance is lower than 4Ohm just put a 4to 10 Ohm resistor in series.

[DPARK]

Let's write in English. That's okay. 

So, my electrical background as a undergraduate mechancial engineer isn't very well. And I don't have any PRACITAL experience.

There are 1,5 weeks left during my internship in the States and I definitely want to get a few results. Since I am working alone on this

project the NI forum is my only help. 

I attached a picture of a amplifier but I dont know how to use it because I only get a "open" signal now.

That means, I need the amplifier   AND the circuitry? What component is a 555? Do you mean IC555? I have to buy this components but I don't know which one I should buy. I really need your help with that. After I get the "right" signal, I can try to work with LV.

Thank you for all your help. I really appreciate it.

Simon