0 Replies Latest reply on Oct 26, 2017 11:39 PM by paulcreaser_1517661

    CY8CKIT-022 Liquid Sensing Shield:- A question about the water height calculation

    paulcreaser_1517661

      We have a Cypress Liquid Level Sensing Shield. Cypress has a pdf explaining the water height calculation (link below) on pages 12 and 13. The calculation works reasonably well with the Liquid Level Sensing Shield.

       

      http://www.cypress.com/file/218531/download

      LIQUID_LEVEL_CALC.PNG

       

      A colleague was interested in the calculation method and made his own basic assumption. The starting point was the capacitance was related to the area exposed to the water and air and the relative permittivity of the two materials. Using excel he came up with the above graphs. The practical results are significantly better than what we see from the above graphs.

       

      The basic equation is simply a copy of the Cypress equation.

       

      Sensor 0 = Air Permittivity * Area Covered by Air  + Water Permittivity * Area  Covered by Water

      Sensor 1 is calculated using the same idea.

       

      The height is calculated as follows:-

       

      height = K * Sensor 0 /( Sensor 1 + Offset)

       

      I understand the model is probably oversimplified, but I'm curious about why and how the results are different.