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PGA450 With Dual Transducer Configuration

Gabriel Hein
Prodigy 90 points
Other Parts Discussed in Thread: PGA450Q1EVM, PGA450-Q1

Hi,

I am trying to develop a reflective ultrasonic distance measurement solution. I need to measure distances ranging from about 5cm on the low end, up to about 100cm maximum. I'm primarily looking for maximum precision (<1mm) and high measurement update rates (>10Hz).

My understanding is that it is not possible to measure distances less than about 10cm using a single transducer configuration due to ringing. My question is whether there is any issue with using separate Rx and Tx transducers with the PGA450 to get around this issue. If this is possible, could the EVM be hacked to facilitate development with a dual transducer configuration?

I'm also curious about what transducers would work best for my application and if it is even possible to hit my specs but that may need to be a different thread.

Thank you for your help,

Gabe

  • 0
    TI__Mastermind 27950 points
    Gabe,
    You could definitely use a dual transducer configuration to decrease your measurable minimum distance to 5cm. To accommodate this on the PGA450Q1EVM, open jumper XFRM (JP3) such that the excited transducer is disconnected from the echo return input path. Connect the receiving transducer's pins to the XFMR RETURN net (via the test point or pin 2 of JP3) and GND.

    With regard to the transducer type, you must first consider the environment that the transducer is exposed to. If exposed to outdoor elements such as rain, dirt, or dust, then a closed-top is necessary. Otherwise, you could consider an open-top transducer, especially for the receiving sensor, which will require a much smaller peak-to-peak excitation voltage and is more sensitive in the receiver state due to a lighter vibrating diagram.

    Since you are targeting less than 1m, you have plenty of options. Most importantly, you may want to consider a high-frequency transducer to achieve higher resolution. We specify the PGA450-Q1 to have a 1cm resolution, but through manipulation of software for short distance modes, less than 1cm resolution is possible. However, I am not certain about achieving a resolution of <1mm. What type of application is this (if you don't mind sharing)?
  • 0 in reply to Akeem Whitehead
    Prodigy 90 points
    Thanks for the great information on the EVM and the transducers. I went ahead and ordered the EVM.

    This will be used on a vehicle and will be moderately exposed to the elements so I guess closed-top will probably be necessary. On the positive side, there will at least be a nice hard perpendicular target to reflect the sound.

    Is the PGA450 limited to 40-70kHz transducers? I see that these are the min and max bandpass filter center frequencies but wasn't sure if the burst generator clocking was also limited to this range. When you mentioned high frequency transducers what range were you thinking? I can certainly try out several different transducers if I can find a source for them.

    Thanks again for your help.
  • 0 in reply to Gabriel Hein
    TI__Mastermind 27950 points
    Gabriel,
    Thanks for separating your new question into a different post. For others' reference, the discussion was moved to: e2e.ti.com/.../443945