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Original question:

PGA460-Q1: PGA460 - OWI Interface.

PGA460-Q1: measuring short distances.

Jonatan Cegoni
Prodigy 175 points
Part Number: PGA460-Q1
Other Parts Discussed in Thread: PGA460

Hi Akeem,

We are testing the product and some customers have reported that the sensor is oscillating the distance value when the obstacle is near. As we use the closed type sensor, I know that detection for distances less than 30cm is complicated, would there be any way to solve this distance value variation when the obstacle is near (<30cm)? Doing some tests here on the bench, I identified the following situation:

1 - Obstacle is physically at 70cm:

 

2 - Obstacle is physically 30cm:

 

3 - Obstacle is physically at 20cm:

 

Note that in this case the distance begins to vary (is reporting >80cm).

  • 0
    TI__Mastermind 27950 points

    Hi Jonatan,

    Based on your last echo data dump waveform, the PGA460 is blind to the 20cm object because it is masked/absorbed by the burst-decay energy. Because the object does not exceed the threshold, the PGA460 will not be able to report sub-30cm measurements. The reason it reports a longer distance is because the echo bounces between the transducer and object multiple times, resulting in what appears to be a longer range echo detection.

    If you need reliable sub-30cm detection, you should use a higher frequency transducer, or reduce your time varying gain range from 58-90dB to 32-64dB with your existing transducer. Minimizing the gain will allow you to see more of the burst-decay to better wrap the threshold mapping and enable downwards of ~20cm short range detection.