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FDC1004QEVM: Questions about using FDC1004 in production for liquid level sensing

Jeff Lam1
Prodigy 40 points
Part Number: FDC1004QEVM
Other Parts Discussed in Thread: FDC1004

Hi, 

I am currently evaluating FDC1004 using FDC1004QEVM for liquid level sensing. I have a few questions related to FDC1004 but before going to the questions, here is a little background of the application:

We are planning to use FDC1004 to estimate the water level inside the water tank of a hydroponics system. Because it is a hydroponics system, pH buffer and nutrient additive will be added to water regularly to ensure proper nutrient is being provided to the plants that are growing inside the system. 

Questions:

1. If we were to use this in production, is there any recommended calibration procedures?

2.How do we calculate the gain and offset compensation value? Can we expect to use the same gain and offset compensation values for production or we will need to calculate these during calibration? 

3. I suspect the property (dielectric constant) of water will change slightly when we add pH buffer and nutrient additive into the water tank. Do you think capacitive sensing is even suitable for our application? If not, do you have recommendation on other TI sensing products that are more suitable for our application?

4. I realized the Rigid-flex circuit doesn't come with the FDC1004QEVM kit. Is there a way we can purchase or get it from you for evaluation purposes?

Thanks,

Jeff

 

 

  • 0
    TI__Expert 7599 points

    Hi Jeff, 

    Thanks for using our parts and we will be glad to assist on the FDC1004 for the hydroponics project. 

    1) For implementing  calibration we have a guidance in our datasheet on the system offset calibration and also gain calibration. The calibration is very system dependent and sensor design dependent. Depending on the accuracy that needs to be measured the calibration can be performed once at power or upon every powerup. 

    2) We do have an app note here that discusses Gain and Offset calibration of the FDC1004 in a liquid level sensing application. How to Calibrate FDC1004 for Liquid Level Sensing Applications This app note provides guidance on configuring the Gain and offset registers. When at production an assessment needs to be made if the calibration needs to performed at regular intervals depending on the accuracy you achieve with the sensor design. 

    3) The FDC1004 is meant for liquid level sensing applications. If your liquid which is water is mixed with other nutrients the concentration will change. FDC1004 wont be able to measure the change in concentration. If the additive is significant enough that the level changes then I suppose FDC1004 can be used as a way to measure level and concentration. For level and concentration application I highly recommend our Ultrasonic solutions which is primarily go to technology. I recommend to go through our Ultrasonic FAQ for information on using ultrasonic solution. 

    4) Unfortunately the Rigid-flex circuit isn't available for purchase and we do have the schematics and the layout available to start your own design.