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LDC1614EVM: The value will increase or decrease slowly when detecting distance Aluminium target and sensor

Owen Li
Prodigy 10 points

Part Number: LDC1614EVM
Other Parts Discussed in Thread: LDC1614

Hi Ti engneer:

  We have applied LDC1614EVM on detecting the distance between sensor and target Aluminium. We found a problem about the value from LDC1614EVM we read.

image.pngimage.png

  We put an Aluminium plate onto coil sensor , and we read the sensor from LDC1614EVM, we found the value from coil sensor used to detect the Aluminium will change randomly when sensor and Aluminium not move . 

  Sometimes the reading will increase or decrease, constantly and slowly. And the reading would not return to initial situation. Please refer to diagram.

  Could you please provide some suggestion on How it happen and How we slove this problem?

                                                                                                                            Thanks to your advice!

  • +1
    TI__Prodigy 160 points

    Hi Owen,

    The reason you are seeing this change is due to the resolution of that device. Anytime a converter is being used there will be some level of noise. The LDC1614 provides 28 bits of measurement resolution which allows for the level of detail to notice this noise despite it being within tolerance. These readings are varying by less than a percent but appear to be rapidly changing due to the high precision of the device. I would recommend averaging these measurements if you are concerned about accuracy. 

    Best,

    Amanda 

  • 0 in reply to Amanda Ratliff
    Prodigy 10 points

    HI Amanda：

     Thanks for your reply !  I have a  question about  the relationship between temperature and the precision .

    We use two coils to measure the distance between Aluminiun plate and coil . one coil as measurement ,another coil as reflection coil to reduce the affect of environment .   

    But the temperature between reflection coil and testing coil is different ,the difference is about 5 °C . Whether the temperature will affect the coil ?  If yes , How will the precision change? 

    Thanks for your kind reply!

  • 0 in reply to Owen Li
    TI__Prodigy 160 points

    Hi Owen,

    I will have to check with my team on this. I will get back to you soon.

    Best,

    Amanda

  • 0 in reply to Amanda Ratliff
    TI__Prodigy 160 points

    Hi Owen,

    The simple answer is yes it will affect precision. The precision of the IC will not be affected, but the precision of the coils will. I cannot provide an exact magnitude because it is dependent on your system. If you would like to know the magnitude of this difference, I would suggest taking measurements with the coils having the minimum temperature difference and compare the results with those taken with the 5 °C difference. 

    Best,

    Amanda

  • 0 in reply to Amanda Ratliff
    Prodigy 10 points

    Hi Amanda:

      got it. Thanks for your reply!

         Best

    Owen