LDC1101EVM: Sensing Through Titanium Plate

Nicolas Hazboun

Part Number: LDC1101EVM
Other Parts Discussed in Thread: LDC1101, TMAG5170

Hello TI Support Team,

I hope this message finds you well. I am working on a project that involves position sensing of a titanium mass using the LDC1101-EVM. We have encountered a significant challenge that we hope to overcome with your expertise.

Project Overview: We are attempting to measure the distance of a titanium mass from a sensing coil. The application requires this measurement to be highly accurate and repeatable under our operational conditions.

Issue Encountered: Our setup includes a titanium plate situated between the sensing coil and the titanium mass. We have observed that the presence of this plate completely shields the target mass from the sensor, resulting in the LDC1101 failing to detect the mass altogether.

Troubleshooting Steps Taken:

We have experimented with various IC settings (Rpmin, Rpmax, Fmin, time constants, etc) but haven't achieved any penetration through the titanium plate.
We've also considered environmental factors and ensured stable conditions during testing.

Assistance Requested: Given the unique nature of our application, we are reaching out to inquire about any specific recommendations or insights you could provide that would enable the LDC1101 to function effectively in this scenario. Specifically, we are looking for guidance on:

Any potential adjustments to the sensor configuration that could enhance its ability to sense through titanium.
Recommendations on coil modifications or alternative designs that might help.
Insights on material properties of titanium that could influence the sensor's performance.
Other products or technologies from TI that might be better suited for our application.

We are open to any suggestions, including exploring custom solutions or any new developments that might be in the pipeline at TI that could be applicable.

Additional Information: We are ready to provide further details about our setup, including schematics, operational parameters, and the results of our preliminary tests.

We appreciate any help or direction you can provide and look forward to your expert advice.

Thank you for your time and consideration.

over 1 year ago

0 Eddie LaCost over 1 year ago

TI__Mastermind 44030 points

Hello NIcolas,

I don't see any way that this could work with inductive sensing. The theory of operation of inductive sensing is to generate an AC magnetic field on the coil, then when a conductive target is brought into proximity of the coil, the magnetic field will induce an eddy current on the surface of the metal target. This eddy current creates an opposing magnetic field which causes a reduction in inductance that the device can sense. As long as the titanium plate is between your coil and target, the plate will build up the eddy current, effectively shielding the titanium mass behind it. The app note below has a good description of the theory of operation as well.

Sorry, but I don't see any way of detecting the titanium mass unless the plate can be moved out of the field of the coil. I think most technologies would have some problem of the titanium plate shielding the actual target.

0 Nicolas Hazboun over 1 year ago in reply to Eddie LaCost

Prodigy 20 points

Thank you for your prompt response. It confirms our suspicions regarding the limitations of inductive sensing in the presence of a conductive barrier.

We are working on a rather unique application where we need to sense the proximity of a titanium mass from inside a sealed titanium cavity. Due to the nature of our design constraints, no electronics can be positioned outside of this cavity. We have managed to devise a workaround that involves placing magnets outside of the sealed cavity and using magnetometers to sense their field changes. However, this approach is not viable for our production environment, where uncontrolled magnetic interference is a significant concern.

Given these circumstances, we are exploring other sensing technologies that might be suitable for our application. Ideally, we are looking for a solution that is immune to external magnetic interference and can operate effectively from within a sealed metallic environment.

Could you suggest any alternative sensing methods or technologies in TI's product lines that might circumvent these issues? Any guidance or recommendations you could provide would be greatly appreciated, as it will greatly influence our approach to resolving this complex challenge.

+1 Jesse Baker over 1 year ago in reply to Nicolas Hazboun

TI__Expert 7950 points

Hi Nicolas,

Since you mentioned exploring magnetic position sensing as an option, perhaps one of our linear 3D Hall-effect sensors like the TMAG5170 and a magnet embedded in the titanium mass approaching the sensor in a head-on configuration could be a potential solution.

I recommend taking a look at our magnetic simulation tool, TI Magnetic Sense Simulator (TIMSS). You can select a device, magnet, orientation, and magnet motion, and simulate the magnetic field density and device output in different scenarios. I've set up an initial simulation of this motion where the magnet is moving from 16 mm to 6 mm above the sensor. I've attached the .json file for the simulation below. You can import the simulation parameters on your own PC following the steps below

go to webench.ti.com/timss/
click "Import design file"
select the .json file
click "Simulate"

At the time of posting this, there seems to be an issue with the sensor specifications being imported into the tool, but this will be resolved soon, and this simulation should still run for you.

Fullscreen TMAG5170_head on.json Download

{
  "version": "3.1.1",
  "design_name": "TMAG5170_head on",
  "magnet_id": 1,
  "poles": 2,
  "material_id": 1,
  "grade_id": 1,
  "select_remanence": "br_average",
  "remanence": 1200,
  "temperature": 20,
  "temperature_coefficient": -0.12,
  "coercivity": 10.9,
  "function_id": 2,
  "magnet_geometry": {
    "magnet_length_x_dim": 4,
    "magnet_length_y_dim": 4,
    "magnet_length_z_dim": 4
  },
  "magnet_position": {
    "x_position": 0,
    "y_position": 0,
    "z_position": 12
  },
  "magnet_angle": {
    "x_angle": 0,
    "y_angle": 0,
    "z_angle": 0
  },
  "magnet_movement": {
    "final_x_position": 0,
    "final_y_position": 0,
    "final_z_position": 2
  },
  "sim_setting": {
    "step_size": 0.1
  },
  "sensor": [
    {
      "sensor_id": "TMAG5170",
      "sensor_position": {
        "x_position": -0.27,
        "y_position": 0.04,
        "z_position": -4
      },
      "sensor_angle": {
        "x_angle": 0,
        "y_angle": 0,
        "z_angle": 0
      },
      "custom_inputs": {
        "variant": "TMAG5170A1QDGKR",
        "applied_vcc": 3.3,
        "temperature_compensation": 0,
        "averaging": 1,
        "maximum_input": 100
      },
      "id": -1
    }
  ]
}

I can't think of other sensing methods that could solve this problem. Our team supports magnetic, inductive, capacitive, and ultrasonic sensing, but it seems those may all be ruled out as options in this case.

Best regards,

Jesse

0 Nicolas Hazboun over 1 year ago in reply to Jesse Baker

Prodigy 20 points

Hi Jesse,

Thank you for the information. I appreciate you guys taking the time.

Sensors

Sensors forum

LDC1101EVM: Sensing Through Titanium Plate