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LDC1612: Measuring cast iron thickness

Dan Hellgren38
Intellectual 530 points
Part Number: LDC1612

Dear Sirs

I have a tool made of cast iron which is 50mm thick.

This tool is worn down into 20mm, so I would like to, continiously and very roughly, measure the thickness (4mm accuracy). I will do this measurement once per day, or less.

The tool is exposed to high G-forces and is cost sensitive so an ultrasonic transducer will not work.

I was thinkin about the LDC1612 running at 1KHz.

The measuremen will be done when the tool is at rest.

I saw a formula at the FAQ giving

    Maximum thickness we can see through = 503 * sqrt(0.75uΩm / (1kHz *1)) = 13.7mm

So my question is: is it possible or not to measure steel thickness 20-50mm with these components ( or other components) or not accordingly to your expertice knowledge?.

/Dan

  • 0
    TI__Genius 13650 points

    Hello Dan,

    at 20-50mm, the metal to be measured is very thick. At 1 kHz, 50mm of iron is >10 skin depths; at 20mm, it is >4 skin depths. 

    This spreadsheet includes a handy skin depth calculator: http://www.ti.com/lit/zip/slyc137

    I'm afraid it is unlikely that this measurement approach will provide good results.

  • 0 in reply to Ben Kasemsadeh
    Intellectual 530 points

    Hi Ben

    Thank for fast and very good reply.

    The Excel sheet was perfect.

    I have a follow up question that maybe isn't for this forum.

    I know that the LDC1612 can only go down to 1KHz.

    Do you think it would be possible to make a design, using descrete components, running at 100-200Hz?

    I can even lower my needs. I don't need to sense 50mm. I could probably be happy if I could sense if I have more or less than 20mm (roughly) cast iron thickness.

    I need a design that simply says that the tool is almost worn out and soon needs to be replaced.

    Is such a design posible? or is there a physical reason that the LDC1612 stops at 1kHz?

    Best regards

    /Dan