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Inductive Sensing of Metal

Jaykrushna Puranik
Prodigy 30 points
Other Parts Discussed in Thread: LDC0851

Dear All,

May I know if any of our Inductive Sensing IC can be utilized for detective a small Screw made of Titanium Metal?

The Screw Length would be in the range of 5 to 10 mm, and the Screw Diameter is approximately 2 to 3 mm.

I need the absence / presence detection, but if it can detect sensor to target distance which will be always less that 10 mm, it would be great!!!

I do not think there is any necessity of using a Micro-Controller. An Inductive Metal Detector IC, working from a single 3 V Lithium-Ion Coin Battery would be OK for a small hand-held pen-like device.

Kindly advise as below:

1] Can the Metal Part as small as a Screw, of Titanium Metal, be detectable with any of the circuits based on any of our ICs?

2] If yes, which IC Part Number would be the Best or a Good Choice to try-out by me?

3] Any other tips and / or tricks which you can please share with me on this subject?

Sincerely awaiting your important and valuable technical feedbacks.

Thanks & with best regards, - Jay.

  • 0
    TI__Genius 17440 points

    Hi Jay,

    While we have devices that could detect the presence of a screw that size, the titanium material may not be conductive enough. I think that your desired maximum sensing range, the target response, and the coil design could be very challenging. Even our highest resolution device (LDC161x) can only sense up to about 200% of the diameter of its sensor coil with a highly conductive target (like copper or aluminum). The target will yield its best response when the coil is approximately the same diameter as the target, so you would have an absolute maximum range of about 6mm. A titanium screw will likely not be detectable at this distance. In addition, all of our devices have minimum Rp requirements for the sensor coils, below which they cannot drive enough current to keep the LC tank oscillating. With such a small sensor coil it could be very challenging to meet this requirement. Also keep in mind that an inductive sensing solution will be very sensitive to the placement of the pen in relation to the screw. I would suggest looking into these resources for LDC coil and target design:

    LDC Sensor Design (app note)

    LDC Target Design (app note)

    LDC Webench Tools

    LDC Excel Calculator Tool (especially the Spiral Inductor Designer sheet)

    I recommend that you use the LDC161x, which means you will need a microcontroller because the device outputs raw frequency data. We do have two devices that do not require a microcontroller (the LDC211x and the LDC0851), but these are lower resolution than the LDC161x. The titanium material will generate a much smaller response than other materials, so you will likely need high resolution. If your maximum sensing range can be minimized, you could also consider the LDC211x. 

    Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 30 points
    Hi Kristin Jones,

    Thanks a lot for your detailed technical response. I need to to do more study of the App. Notes as suggested by, in the next 2 to 3 days time.

    I will revert in the next week.

    in the mean-time, do you think, there can be any other better solution possible for my application?

    My daughter is a well experienced & well practicing Dental Surgeon. I am doing this for her and one very senior and close friend of me, an expert & renowned Dental Surgeon.

    May I request you to kindly do find time and please discuss this issue with your team of experts on Metal Detection.

    Once again, I will be awaiting your most valuable feedback.

    Thanks & with best regards & respects, - Jay.
  • 0 in reply to Jaykrushna Puranik
    TI__Genius 17440 points
    Hi Jay,

    Unfortunately TI does not have experts on metal detection in general. It's possible that hall sensors could work for this application, but I lack expertise with those devices. I would suggest posting a similar question in their forum to see if their sensors would work for this application. I'd be happy to provide guidance if you encounter issues with the devices, but I don't have another solution that I can fully recommend.

    Regards,
  • 0 in reply to Kristin Jones93
    Prodigy 30 points
    Dear Kristin Jones,

    Thanks a lot for your response.

    I will do some more search on the subject.

    Though, the issue is yet to be resolved yet. for all practical purpose at this stage, I would say, "This resolved my issue".

    Once again, thanks for your feedback from time to time.

    With best regards, - Jaykrushna.