PGA450-Q1: PGA450Q1EVM-S

Hi Eddie,

Here is my test setup:

I am using Cmd1 to trigger short and long burst and reading the buffer respectively. Here is the plot of the Buffer data which I couldn't understand.

Can you please have a look and explain about this response. Are these spikes because of reflections from multiple objects?


Afterwards I replaced cardboard object with some plastic object placed at 100cm. Here is the ECHO data from the sensor.

Isaac Lara Kindly have a look, Thanks.

Best, Taimur

Taimur,

Isaac and I discussed your plots.  

Yes, I think those additional spikes could be from other reflections closer to the transducer.  It would be good to clean up the area so there are not other items nearby, at least for initial testing.  The beam angle of your transducer could also have the effect of detecting other objects if the beam angle is wide on your transducers.  

When testing, also be sure that the angle of the target(cardboard or plastic) is parallel with the transducer.  If the target is angled, the energy of the reflection may not be fully received by the PGA450 receiver.

Are you looking to detect at a fairly fixed range or is there a wide detection range required?  You could also adjust your threshold to be higher in the earlier time, so those earlier reflections are ignored.    

Hi Eddie,

Thanks for the response.

As it can be seen from the test setup, object is placed directly Infront of transducer. Response to long burst is quite random even there is no significant peak which can be considered as valid object detected. I'm not sure what I'm doing wrong. Could it be transducer issuer? 

Regarding our application, we are currently doing preliminary tests, so trying to detect objects in the range of 20 - 100 cm range. 

I am not sure how to proceed further, response of sensor changes randomly even if type of the object is changed while placed at the same distance.

Thanks & Best Regards,
Taimur

Taimur,

There are also other objects nearby that could be affecting the results depending on the transducer beam width.  I recommend moving these items out of the way and re testing.  See the image below with items circled that should be moved out of the path.  

Good day Eddie,

We clean-up our setup and now getting some better results.

With Cmd1 (Short burst) we are getting some offset in distance measurement: e.g.

1.


2.

3.



What could be the reason that we are getting some offset in measured distance from sensor?

Thanks & Best Regards,
Taimur

Hello Taimur,

On the first capture, it does look like the threshold is set too high, which would trigger the threshold at a later time since the transducer takes some time to saturate, which would measure the time longer than expected.  On the other 2 captures, the threshold looks properly configured.  

There is also good information in the thread below regarding the threshold configuration and free running timer that could potentially be at issue.    

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/694551/pga450-q1-distance-measurement-offset 

Hi Eddie,

Threshold is same in all three plots however object distance is different. We will adjust thresholds according to our application.

Regarding offset in distance measurement, in the post you mentioned offset in measurement is decreasing as the the object's distance increases. However in our case offset is quite similar for short and long measurements as seen below:

Also in the post you mentioned I couldn't find solution other than just to optimise threshold values, or am I missing something?

Best,