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LDC1000 Alternative Target Materials

Claudia Visentin
Prodigy 30 points

Hello, 

we are mounting LDC1000 sensors on a mechanical structure and need to place the target material in front of them. 

We used the WEBENCH Design Center Tool to determine the right target material and the result was: SS416 (we know it as 1.4005).

The solution purposed by the tool is difficult to find for us. Can we reach the desired measurement precision also using other materials? If yes, which materials can we use?

  • 0
    TI__Expert 6550 points

    Hello Claudia,

    First, I would like to know which measurement are you using (L, Rp, or both)? If you are using L measurement only, Aluminum would be a reasonable substitute for SS416. It is more conductive which will leads to larger inductance change and better resolution (please note that Al is not implemented in WEBENCH yet so we ask you to approximate it by using Cupper simulation). If you are using Rp measurement, SS416 would give you better results.

    Best Regards,

    Natallia Holubeva

  • 0 in reply to Natallia Holubeva1
    Prodigy 30 points

    Hello Natallia, 

    Thank you for your reply. 

    For us it is not critical which measurement we use (L, Rp, or both). For our application we need to have a sensor with following data:

    Diameter: 1.17 cm

    Resolution: 0.08 um

    The only material in the WEBENCH allowing us to satisfy these characteristics is the steel SS416, but we can't find it on the market.

    Is there an alternative to this Steel? For us it is not important which material we use, for us it is important that the material we use ensures the desired resolution and diameter. 

    Can you suggest us an alternative?

    Thank you, 

    Best Regards, 

    Claudia Visentin

     

  • 0 in reply to Claudia Visentin
    TI__Expert 6550 points

    Hello Claudia,

    Please try the simulation of L measurement with Cupper. You could switch to Aluminum for your setup.

    Best Regards,

    Natallia Holubeva

  • 0 in reply to Natallia Holubeva1
    Prodigy 30 points

    Hello Natallia, 

    1. We tried the simulation of L measurement with Copper and we could not get the desired resolution. Would it mean that we can't reach the desired resolution neither with Aluminium?

    2. If we have  the following situation:

         - diameter of the coil = 1.17 cm

         - diameter of the target material of 0.6 cm

    would the resolution calculated by the webench tool be the same or would this affect the measurements?

    In other word, does the diameter of the target material have to be bigger or equal than the diameter of the coil or is this irrelevant?

    3. On the charts we get on the Webench Tool there's a graph "Resolution vs. Distance" Does the term "revolution" refer to the resolution of the estimated distance?

    4. How is it possible to calculate the distance between target and sensor by mean of the inductance L only? We found on the datasheets only a description about how to calculate Rp depending on the proximity data that we get from the sensor but nothing about the inductance.

    Thank you very much, 

    Claudia

  • 0 in reply to Claudia Visentin
    TI__Expert 6550 points

    Hello Claudia,

    1. Alunimum and copper have similar properties. Please note that copper is slightly more conductive, so the resolution with it is slightly better than aluminum. I suggested Aluminum because it is more practical.

    2. By the rule of a thumb, your target should be the same size as the coil and the useful distance range you can sense is half the diameter of the coil. Please, try increasing your target if you can.

    3. Yes.

    4. As the target moves away from the sensor, the inductance will change due to the coupling. Therefore, frequency will change.

    Best Regards,

    Natallia Holubeva