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TDC1000 TDC7200EVM Sensor Output

kerem yasar
Intellectual 560 points
Other Parts Discussed in Thread: TDC7200EVM, TDC1000

Hi everybody,

I am trying to implement a flowmeter using "Steminc 15mm 1Mhz transducer (SMD15T21R111WL)" , which comes with TDC100 TDC7200EVM package.

Before connectiong the sensors to my board, I am trying to drive one of them with signal generator and observe the receiver sensor with a scope. I am running the sensors with 1Mhz square wave(also tried sinusoidal wave), however; no matter how close I bring the two sensors, the scope that is connected to the receiver piezo disc  shows no signal.. All I am getting is noise on the scope..  I brought them to a 1 cm apart but still there is no signal on the scope from any distance.. I am driving the transmitter disc at 1Mhz and 3.3V peak to peak signal (low level is 0V and high level is 3.3V).

What should be the expected signal level on the receiver piezo disc ? What might be the reason that I can not observe any signal (except noise) on the scope that is connected to the receiver piezo disc?

Any suggestion is deeply appreciated, thank you all..

  • 0
    TI__Mastermind 21685 points
    Kerem,
    Air is very absorptive and you need high transducer excitation voltage. Also, it's best if the transducers are properly mounted to avoid losses. Check link below for a number of application notes

    www.ti.com/.../technicaldocuments

    Also, check
    e2e.ti.com/.../498792


    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Intellectual 560 points

    Thank you a lot for your response,

    My custom hardware runs from a single cell lipo battery, I need to run the sensors with 3.0V. What is the best frequency for the air so that the signal will not be attenuated/absorbed ? TOF measurement distance is 4 to 6cm. (Sensors are 4 to 6 cm apart from each other)

    I have also tested Steminc SMD10T2R111WL which is a 215khz transducer, yet , I did not observed any signal on scope.. Do you think that piezo ceramic discs are right choice for 3.0V excitation ? 

    Thank you for your help

    Kerem

  • 0 in reply to kerem yasar
    TI__Mastermind 21685 points
    When you are experimenting with different transducers make sure you are hitting it at its resonant frequency. TDC1000 CONFIG0 register gives you the option to choose what's the transmit clock divider. You can choose the TDC clock source in Setup tab. You might have to use the CPU_CLK option for lower than 1MHz.

    I am not sure if you can get sensor working with 3V. Sensing frequency is inversely proportional to the sensing distance. Also, as the transducer freq decreases, the blind zone (unusable area near the transducer) increases. You can read more at the link below
    www.ab.com/.../Sensing-Range-and-Effective-Beam.html

    Thanks,
    Vishy