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Problems with wall adhesion

Florian Recla
Prodigy 20 points
Part Number: TIDA-00317


Hello,

i've made a liquid level sensor following your "TIDA-00317" reference design. The sensor is placed on a custom PCB that is glued to the container wall (2mm plastic). 

If there is water in the container, the sensor works very well. However, the sensor should measure a fluid that sticks a bit to the wall. When the container is filled for the first time, the measured level rises correctly, but after the container is emptied, the measured capacity remains the same as when the container is full, because a film about 1mm thick remains on the wall.
Is there a way to change the design of the sensor so that the 1mm film does not affect the measurement?

Thanks,

Florian

  • 0
    TI__Mastermind 18545 points

    Hello Florian, 

    The issue with changing the sensor is you will always have a different data when there is a small coating of the liquid on the wall compared to before any liquid was present. We have found that the best approach to this issue is to coat the container walls with something that prevents the liquid from sticking as much. Assuming you can't change liquid, a wall coating is the best option.

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Prodigy 20 points

    Hello Justin,

    Thanks for the quick reply! I will try to find a coating that prevents the liquid from sticking. Is there anything that i could change on the sensor side to be able to detect if there is just a small film on the wall or a larger amount of fluid?

  • 0 in reply to Florian Recla
    TI__Mastermind 18545 points

    Hello Florian, 

    You could try to detect the change between the 1mm coating and when the liquid is filling the container but this might end up creating some overlap in capacitance readings depending on the actual level of the liquid. For example, if the liquid is halfway down the container but the coating is still all the way up to the max level, the capacitive reading might just look like the liquid is at a level in between the two. This is why we typically just recommend coating the wall to reduce the liquid sticking to it. 

    Best Regards, 

    Justin Beigel