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LDC0851: Determine Sensing Distance For Target That is Smaller Than Sensor

Greg Prodzenko
Prodigy 10 points
Part Number: LDC0851

I have an application where I need to detect a ferrous metal at a minimum 1.75mm and my target is only 5.3mm in diameter. I am having difficulty designing a sensor that will meet all the requirements for this device and would like to know that the effect will be of having a target that is smaller than the sensor. Is there a way to calculate the change in sensing distance? Alternatively, could I increase the detection sensitivity by using more than two layers on my sensor? If so, how could I calculate this?

  • 0
    TI__Genius 10080 points

    Hi Greg,

    Thank you for posting to the Sensing forum.

    In order to maximize the inductive response the target should be at least as large as the sensor coil, but the coil should not be larger than the target (see our Inductive Sensing FAQ). If the target is smaller the coil will have reduced sensing distances. In general, LDC devices can sense at a distance up to 50% of the sensor diameter.

    I recommend using the Inductive Design Sensing Calculator Tool to enter sensor parameters and see what combinations will fit within the device specifications of the LDC0851. You can enter parameters such as number of layers, trace width/spacing, diameter, number of turns, LC tank capacitance, and temperature. You can also enter the target distance and see the calculated frequency and inductance of the sensor. Additionally, the LDC Sensor Design application note has further details on optimizing sensor design for a system.

    Best regards,

    Nicole