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LDC1101: LDC1101 sensor design optimization

Scott Stelick
Prodigy 20 points
Part Number: LDC1101

Hello;

      I recently starting working with the LDC1101EVM system to measure axial movement over a range of 0-1mm.  The target is a titanium cylinder and the sensor coil is a legacy design consisting of 60 coils of wire around the exterior end of a titanium tube.  The coil is measuring the interior titanium cylinder as it moves.  The cylinder is 8mm in diameter and the coil is 4-10mm in diameter donut.  Using the LDC1101-EVM, we have measured the axial movement of the cylinder but we are looking for more response.  Questions that I have are:

1)  If we decrease the diameter of the sensor under 8mm, would the signal improve?

2) Obviously having a titanium shell between the target and sensor coil will reduce the signal, is there a method to reduce the loss?

3) Would multiple layers of wire improve the signal or just add noise?

Thanks for any help.

Scott

  • 0
    TI__Mastermind 18545 points

    Hello Scott, 

    Decreasing the sensor to be the same size as the target may result in a larger inductance shift but this can impact the max range. If the 0-1mm range does not have any notable offset from the sensor, then this will not be a problem for your application. Adding layers to the wire is also another way you can boost the strength of your signal. This will also help with the loss you are getting from the titanium shell. 

    Best Regards, 

  • 0 in reply to Justin Beigel
    Prodigy 20 points

    Thanks for the tips.  We are trying to use the LDC1101 to replace an existing eddy current sensor that uses 41 QML wire to form a circular coil around the end of the outer cylinder shell.  All of the literature online at TI mentions copper as the preferred metal patterned on a PCB.  To wrap around a cylinder would 41 gauge copper (round wire) operate with the LDC1101?  

    As for my application, the sensor coil and inner titanium cylinder is approximately 2mm apart thru a 200 micrometer thick titanium shell so sounds like I would need multiple wire layers which be wrapped on top of each other or have a separation layer in between to allow wrapping direction change?  I appreciate your knowledge on this application.

    Scott

  • 0 in reply to Scott Stelick
    TI__Mastermind 18545 points

    Hello Scott, 

    If you can determine the inductance or resonant frequency of the sensor coil then that information would determine if it will work with the LDC1101. You can do this by measuring it with a network analyzer. 

    Both methods will increase the inductance of the coil but with wire wound coils, these two methods will have slightly different impacts than with the PCB coils. We have calculation tools available for PCB but not anything for wire coils so it may be best to build each and see what the inductance of each variant is to determine how well it will work with the LDC1101. 

    Best Regards,