Hello,

I would like to make a metal detector strong enough to detect a piece of stainless steel tape in the cable that we make.
We make electronic/electric cable, for example, sometimes this cable is bad and from the 50,000 feet we make, we have to cut it 3 times (we call that splices) because cable had a cosmetic defect so we cut that part out, now, we solder these splices to make one single cable so we can put the final plastic cover to make it one single piece without setting it up 3 times because of the splices.
I was thinking to make the detecting coil around a 2" or 3" PVC pipe so the cable/wire goes through and it will be easy to detect. It has to be strong enough to detect a 1/4” inch tape with 0.004” thickness that we want to put around these splices so they can be detected, make a beep and turn a red light, connect it to an 110 volt.
It needs to detect on 18-8 stainless steel tape, no iron, no copper, no aluminum, no silver, no gold, There are so many tutorials to make one online but I need this one to be strong and able to detect it.

Any help will be appreciated.

Thanks in advance

 

Let's start with the definition of 18-8:
73% iron and

• Their carbon content is generally held to a maximum of 0.08%
• They (generally) have 18% chromium
• They (generally) have 8% nickel
• They are non-magnetic
• They cannot be hardened by heat treatment
• They can be hardened by cold working the material (“work hardening.”)

Now it's up to somebody else to say which properties of that mixture are different from copper and plastic in a way that a magnetic field or an RF field will reveal.

It seems to me that x-rays would work, but a magnetic field is a lot cheaper to bring to the job.
Is there an option to use a different kind of marker?

OK, now I'm guessing:
It's very easy to ohm this stuff. That seems to mean the chrome oxide layer is conductive. If the adhesive doesn't insulate the ends of the tape from each other, or there is no adhesive, it might be seen as a shorted turn. Is the marker installed as a turn around the bundle or is it laid in lengthwise?

 

Is the cable uniform, except the splice area?
How fast is this cable moving?
I think we need some kind of illustration of what this splice looks like, and more details.


Depending on the cable and splice geometry, a capacitive sensor might work better, then the magnetic properties of the materials are not important.

It might be as simple as calibrating for the nominal cable, then looking for changes in capacitance caused by the metal foil.

 

It needs to detect on 18-8 stainless steel tape, no iron,

But if 18-8 SS contains 73% iron, won't that be a problem?

 

What about using the same equipment for detecting the pipe underground? It could be modified and simplified for the production line. Depth functions would not be needed and the transmitted frequency could be tuned in to provide almost instant breaks.