BOOSTXL-PGA460: Ultrasonic Detection with IP65 Enclosure.

Hi Frank,
To better understand the application, can you answer the following:
1) What is the targeted object? You mention this is an outdoor application. Can you provide additional detail about the use-case?
2) What is the maximum distance requirement? With a record length of 36ms, your maximum range is about 6m.
3) What is your minimum distance requirement?
4) How is the transducer mounted to the IP65 enclosure?
5) What is your supply voltage or transformer's center-tap voltage?

To help you debug this issue, I'll need the following:
1) Echo data dump plot from the GUI's Data Monitor page of your preset 1 or 2 burst-and-listen profile.
2) Oscilloscope capture of the transducer's excitation voltage (probe the positive transducer terminal).
3) System diagnostic capture from the GUI's diagnostic page. Specifically, I'm looking for the frequency and decay diagnostic values.

Yes, any object that blocks the transducer (such as a leaf or paper) will limit to field-of-view/range of the transducer.

Hi Whitehead,

Thanks for the reply.

1)  What is the targeted object? You mention this is an outdoor application. Can you provide additional detail about the use-case?

[Neville]: use case is for detecting vehicles (for parking occupancy sensor).

2) What is the maximum distance requirement? With a record length of 36ms, your maximum range is about 6m. 

[Neville]: Max distance requirement is 1m now I have changed record length to 8.192ms.

3) What is your minimum distance requirement?

[Neville]: Min distance requirement is 10cm.

4) How is the transducer mounted to the IP65 enclosure?

[Neville]: Currently for testing purpose we are placing the sensor inside the enclosure (not mounted). We require your valuable advice regarding the mounting of the sensor in IP65 enclosure.  

5) What is your supply voltage or transformer's center-tap voltage?

[Neville]: Power mode is standard mode; external supply voltage is 8.6v-1A at j5.

To help you debug this issue, I'll need the following:

1) Echo data dump plot from the GUI's Data Monitor page of your preset 1 or 2 burst-and-listen profile.

[Neville]:

Echo data dump plot when sensor inside enclosure.

Echo data dump plot when sensor outside enclosure.

 

2)    Oscilloscope capture of the transducer's excitation voltage (probe the positive transducer terminal).

[Neville]:

                 

3) System diagnostic capture from the GUI's diagnostic page. Specifically, I'm looking for the frequency and decay diagnostic values.

[Neville]:

 

Settings used for the above echo data dump plot

Yes, any object that blocks the transducer (such as a leaf or paper) will limit to field-of-view/range of the transducer.

 

[Neville]: For the above shown settings I am keeping sensor outside enclosure, and placing a paper with thickness less than 1mm in front of sensor and placing an object 50 cm away from sensor, but now object is not detected. Below shown is the echo data dump plot.

 

Thanks and Regards,

Hi Neville,
I may now have a better understanding of your problem. When you say the sensor is inside the enclosure, are you trying to transmit and receive through the enclosure? You will not be able to easily do so with air-coupled ultrasonic transducers, especially if you have not mounted the transducer to the surface of the enclosure using an coupling-agent or adhesive.

We have not done a significant amount of testing, but air-coupled transducers perform very poorly when the echo is expected to propagate through material. Because of the large acoustic impedance mismatch of air versus most solid materials, most of the energy is reflected at the inner surface of the enclosure where the transducer is mounted. This is the same reason most automobiles are not able to hide the ultrasonic transducer behind the bumper, so the sensor must remain visible. Radar technology, on the other hand, is able to propagate through various materials more effectively.

This is why your performance with the sensor outside of the enclosure is much better, and you can actually see the return echos. If you are going to continue experimentation with the sensor inside the enclosure, I recommend that you try various coupling agents (glues or epoxies) to reduce any air-gaps that would otherwise be present between the surface of the transducer and inner wall of the enclosure.

I have only been able to successfully detect objects through plastics and polycarbonate up to 0.093” in thickness. I mounted the transducer using cyanoacrylate at the surface, and hot-glue around the sides. Other transmission mediums (glass, acrylic, steel) failed, or require other mounting techniques (to be further explored).

Hi Akeem,

Thanks for the reply.

I will continue experimenting with the recommended coupling agents.

If i am using the sensor outside the enclosure, 1mm thick paper will also be an obstacle only or will ultrasonic signals pass through paper? can you advice me in this situation.

Thanks and Regards,

Neville,
Unless the transducer is coupled to the paper, the majority of the energy will most likely be reflected by the paper. Unfortunately, I do not have any suggestions to offer for paper-to-air medium transmission.