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Small flask liquid level sensing using TDC1000

Oleg Kobrin
Expert 1890 points
Other Parts Discussed in Thread: TDC1000-C2000EVM, TDC1000

Hello!

We got the following task: we have the round plastic container, 33mm diameter and 70mm tall, with some (water based) liquid in it. The container is disposable, and firmly attached transducer is not possible. We need to feed a pipette tip until touching the liquid inside the container (1-3 mm accuracy is ok). We got 2 kind of transducers - SMD10T2R111 and 400PT160 for water and air application.

First I experimented with water application. I glued the 1mHz transduser on the bottom of container and coonected it to my TDC1000-C2000EVM, but with default settings id does not sense the water level at all, and eved does not react on presence or absence of water inside, and nothing seen on my oscilloscope, I got the echo signal on COMPIN, but it does not change the shape.

Then I attached the 400PT160 transducer, and run the EVM again. this time I just trying to see any reaction to moving the transducer near the solid surface, but nothing happend again.

What am I doing wrong?

Thank you!

  • 0
    TI__Expert 4725 points

    Please read my app note that describes how to configure the TDC1000 for level applications  in detail: http://www.ti.com/lit/pdf/snaa270

    To connect to your container you'll need something to make a good acoustic connection. I'd recommend RTV-11 as is good acoustic transmission and is minimally adhesive. I'd also recommend you use a mechanical clip or retainer to downward apply pressure on the container to maintain good contact with your test vessel.

    -regards,

  • 0 in reply to Matthew Minasi
    Expert 1890 points

    Sorry, but it is not the problem. As I noticed before, I firmly attached the thansducer to the bottom of a container with epoxy resin. And in this configuration the liquid level has no effect on the resulting TOF.

    Anyway, the prioritized solution is to use air transducer from the top of container, as the container will be installed into device without any possibility to fix it or apply any compound to the bottom.

  • 0 in reply to Matthew Minasi
    Expert 1890 points

    Here I attached a photos of container with transducer.