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FDC1004: Medical Blood Sensing

Part Number: FDC1004

Customer would like to sense the blood via FDC1004 in medical equipment. 

1. Is this device able to distinguish the blood and air? For example, when probe sensing is touching the blood liquid, Is FDC1004 able to react and reporting to MCU via I2C?

2. Is FDC1004 a suited one device? or any recommended one?



  • Brian,

    The FDC1004 should be able to distinguish between blood and air.

    Having said that, what is meant by "distinguish"?
    Does the customer want to detect just the presence and/or level of blood, or do they also want to detect other properties as well?


  • Thanks. 

    Be more clear, yes! when probe is detected with blood, it needs to informing the MCU by I2C, and then MCU can do the following tasks for medical application. 

    as above application, does FDC1004 work?



  • Brian,

    The FDC1004 has been used successfully in other medical applications, so it could be a good candidate for your application as well.

    One factor to consider while moving forward is that blood is pretty conductive, with an average conductivity of 0.662S/cm (at least according to Google).
    So while the combination of blood and sensors will certainly have capacitive properties, the impact of conductivity on measurements is a bit of an unknown.
    Our experience with liquids has been confined to low conductivity liquids, like distilled water.

    We have had customers with non-medical applications use the FDC1004 to measure liquids that were at least partially conductive, but a lot of details haven't been shared with us.

    I hope this helps. Please let me know if you have any questions.


  • Customer would like to setup a customer's platform of liquid with FDC1004 as plot below. 

    On the EVM sensor board, we found that CIN1, CIN4, SHLD1 and SHLD2 are connected to sensor board. How do we connect main board to customer's test platform. 

    - CIN3 pin connects to Tip

    - Does SHLD pin or GND pin connect to Liquid??? 




  • Brian,

    The customer might get good results by not connecting anything to the liquid.
    They will have to experiment with it.

    If that doesn't work, they may want to try placing a small ground plane on the underside or along the outer surface of the vial holding the blood.
    If they try this approach, they may need to experiment with the size and shape of the ground plane.

    You normally don't connect the SHLD to the thing you want to measure.
    They can use the SHLD to help manage EMI if that becomes a problem in their system.

  • Thanks John/Brian,

    So far we had a good data. We can clearly distinguish between situation in contact with liquids and non contact with liquids. Seems it can be implemented in our design.



  • Shawn,

    That is great news!

    Thank you for letting me know.

    Please update this thread with any questions or concerns you have.