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TDC1000 excition frequency

user550798
Prodigy 40 points
Other Parts Discussed in Thread: TDC1000

Dear expert, 

I have a question about TDC1000 excition signal, which depends on CPU clock or on board oscilator. This excition signal is divided by factor and we can get a fixed series frequencies. 

in real situation, every ultrasonic sensor has a different central frequency; 

Even it is labled 1 M hz, the central frequency of one sensor may be 1.08 M Hz for example. Further more, with the time going on and temperature different, the central frequency of ultrosonic sensor will drift.   

I want to know with TDC1000 solution, how to handle with the sensor central frequency drift and locate every sensor central frequency? 

In gernal method ,  CPU will scan excition frequency near sensor central frequency with small step in every fixed time interval.   

Best regards

Herman

  • 0
    TI__Expert 4725 points

    Herman,

    The excitation frequency table shows what excitation frequencies we have created with the MSP430 utilizing the 24Mhz xtal oscillator on the EVM. Another processor setup may have other options.

    With respect to transducer frequency shift, each transducer has a bandwidth it works within over a temperature range. It’s required to choose a transducer that operates at the excitation frequency over the required temperature range of the application.

    Regards,

  • 0 in reply to Matthew Minasi
    Prodigy 40 points

    Matthew, 

    The  precise measure  is based on xtal oscillator frequency. How we handle with xtal oscillator aging? How we handle with the xtal oscillator frequency drift based on temperature? RTD temperature compensate for the testing liquid and also for the xtal oscillator? What special xtal oscillator need? 

  • 0 in reply to user550798
    TI__Expert 4725 points

    In general a standard inexpensive Xtal oscilator (50ppm) is stable enough to keep excitation within the bandwidth of the transducer. See below:

    8MHz 50 ppm xtal osc drifts 400hz but divided by 8 yields a 50Hz shift at the excitation frequency.

    The transducer you refer to (1.08Mhz) can shift by 80kHz so the 50Hz shift in excitation causes no effect.

    regards,