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PGA460-Q1: Choosing the tuning capacitor without impedance gain-phase analyzer

BERNARD FROMENT
Intellectual 270 points
Part Number: PGA460-Q1
Other Parts Discussed in Thread: PGA460

Hi,

I'm in a bistatic configuation at 58KHz with two audioWell sensors : ref TR58-14K279Z-L12-02

But my sensor data sheet just indicates the sensor's capacity: 2000pF ± 15% (at 25℃,1KHz)  and I dont have the curve phase/gain nor impedance gain-phase analyzer.

I saw that in the e2e forum:

https://e2e.ti.com/support/sensors/f/1023/t/787142?tisearch=e2e-quicksearch&keymatch=PGA460%20Ctune

Is there a way to find this capacity value in a practical way? For example with the test mode, sweeping frequency from 30 to 80KHz ?

I try to test sweeping the main sensor frequency but it's difficult to analyze correctly the results.

I find the signal emitted is maximum at 52KHz and at 65KHz

Above you have screenShots: first at 52KHz, second at 65KHz

Has somebody experienced a "handy"method to tune this capacity ?

Regards

Bernard FROMENT

Electronics Engineer

  • 0
    TI__Genius 11015 points

    Bernand,

    We have received your question & we will get back with you by next Monday.

  • 0 in reply to Bharat Aravamudhan
    TI__Genius 11015 points

    Bernand,

    Sincere apologies for the delay, our Application Expert for the PGA460 is on vacation & we will get back with you on this before this Friday.

  • 0
    TI__Mastermind 27950 points

    Hi Bernard,

    Transducers are high-Q systems with narrow operating bandwidths, so you should always set your PGA460 frequency to the center frequency of the transducer, which is 58kHz for the TR58-14K279Z-L12-02. Any value beyond +/-2kHz will likely result in no echo generation or detection.

    Considering the number variables and lack of model information most transducer datasheets provide, you will need to manually sweep the external tuning capacitor and damping resistor values.

    From the PGA460 Ultrasonic Module Hardware and Software Optimization app note:

    Typical values for tuning capacitance ranges from 100 pF to 2000 pF. When driving the transducer in half-bridge configuration and full-bridge, configuration resonance is primarily dependent on the transducer and therefore a tuning capacitor is not required...Given that the value of RDAMP ranges from 500 Ω to 25 kΩ, TI recommends to use a potentiometer to sweep and finetune the value for the specific sensor, driver, and component combination.

    You can sweep the external tuning capacitor in steps of 100pF and the damping resistor in steps of 1kOhm.