Hi Isaac,

I will try to play ard with short Tof measurement mode and come back to you after that, thank you very much

Rgds,

Chin

Hello Chin,

Of course, please let me know if any other assistance is needed.

Best,

Isaac

Hi Isaac,

i wanna confirm with you on the on wire connection, TX1 >> positive + transducer and Gnd >> negative - transducer for water tank level sensor correct?
also does the CA glue is necessary to apply? 

thanks,

Chin

Hello Chin,

That is correct, I confirmed your connections were correct when you submitted the post. Make sure you have the correct channel is selected as well as the listening mode. If the wrong is selected the device will try to listen on the wrong TX and RX combination on the board. 

The CA glue is necessary because we need to ensure good mechanical connection to the tank. Without this mechanical adhesion the signal might not travel through the tank and just be reflected by it instead. CA is just super glue so it should be fairly easy to find.

Best,

Isaac

Hi Isaac,

ya, currently i am using TX1 channel.

the reason i didnt applied the super glue is that i still havent finalize the tank dimension, i wanna save the transducer for the final tank.

thanks,

Chin

Hello Chin,

Thanks for the confirmation. This could be the source of error you are getting, since the transducer is not making proper connection with the tank the wave is not propagating through the system appropriately. You might have to begin testing once you have finalized your tank dimensions and printed a new tank.

Best,

Isaac

HI Isaac,

may i confirm with you with 1 thing, can i say that there is no other way that we can test it without using super glue (proper connection) to the tank? 
if let say i put the transducer at the bottom without any super glue, just use my finger to press it, will this also cause the error i am getting it?

thanks,

Chin

Hello Chin, 

Sorry for the delay.  We are just coming back from the holidays.  Isaac should be able to take a look at your most recent questions tomorrow.

Regards,

Mekre

Hello Chin,

Thanks for the patience as we were out of office for holiday. But I have tried this in the past and have not had good success by simply pressing the transducer into the tank. It is also possible that you still have not configured your listening window correctly. If you provide me the water level you are trying to measure as well as the speed of sound in the liquid you are trying to measure I can try to suggest some settings.

Best,

Isaac

HI Isaac,

my plan is to try out to different tank small container and medium/large container, i will share you the small container first. 

110mm x 140mm x 58mm (height)
1M 15mm steminc transducer

water level 
20mm (green sticker)
30mm (pink sticker)
40mm (orange sticker)

i got ard 38us for all these 3 layers

thanks,

Chin

for big container, i am just using normal water 

128mm diameter 
160mm height

water level 
50mm (green sticker)
100mm (pink sticker)
150mm (orange sticker) >> did not try

i got ard 52us on both level (50mm and 100mm)




seem like i am not getting the real source or echo form the transducer correct?

thanks,

Chin

Hello Chin,

For your small tank you didnt mention what the speed of sound would be or the type of liquid you are measuring so I just assumed water. That means your ToF should be approximately 27us-54us (20mm-40mm) with your current settings you are not actually listening to the echo until about 36us which means you would never be able to capture your shortest ToF. Here are my settings for ~22.5mm of water achieving a 30.5us ToF.

For your large tank your ToF should be approximately 67us-202us (50mm-150mm) so the standard ToF is fine for this tank since you begin to listen at about 52us, you could probably reduce the time of listening window but keeping it large shouldn't be a problem.

If you notice both of your measured times are triggering pretty much right after they activate 38us for your small tank when listening starts at 36us and 52.5us when your listening starts at 52us. Meaning that you could have more than the required gain on here or that you are accidentally triggering on the ringing. But both of these are false measurements. I would try to probe your transducer connection to see what you could be possibly be measuring. If you noticed for my small measurement I turned off the PGA since the measurement is so small you do not require that much gain. Although I still believe that part of the problem is the way the transducer is mounted to the thank.

I hope this helps!

Best,

Isaac

HI Isaac,

yup, you are right both are using water. i had tried the setting you has suggested above but still failed. 

anyway i managed to find a BPU-P7-1000B-W200 (7mm 1Mhz) transducer to be to scarified for this experiment. i had applied with super glue than follow up with hot glue gun.  

the TDC value not stable (random number in us) and there is no stop signal to be found in the scope below



any idea? seem like the connection between the transducer and the tank is not as easy as i think. 

may i know what kind of tank/material you are using?

thanks,

Chin

Hello Chin,

I am using an acrylic tank kind of like the one pictured in this document but bigger. If the tank you are using is not one solid material and has air gaps in between this could be very problematic for the ultrasonic signal since it would get deflected as it reaches the next material boundary.

I am assuming your markers are where you expect the stop signal to be and is the pink signal your COMPIN output?  Whats the level being measured here?

Best,

Isaac

HI Isaac,

The markers was from previous measurement, yes the pink signal is the comp in output, the level is ard 20mm-23mm.

thanks,

Chin

Hello Chin,

Thanks for the info, small measurements in this range can be pretty difficult to make, my suggestion would be to increase the level a bit and try to do a larger measurement first then work your way to a lower measurement.

I would also recommend probing the TX signal over the START pulse just so that you can see the burst profile. The comparator looks like its activating at the proper time but the signal that I believe to be the echo looks rather small, this might require some more gain or perhaps try increasing the amount of pulses to increase the measurement SPL. 

Best,

Isaac

HI Isaac,

thanks for the suggestion. 
I will try to probe the TX signal next week.

another question, ABS material print out from the 3D printer is okay to use right ? if yes what is recommend thickness

thanks,

Chin

Hello Chin,

I have not tried ABS before, but I believe it should work if you have the infill set to 100%. If you have the infill set to a lesser value there might be some airgaps between the outer walls which the ultrasonic energy would have to travel through. I think 3mm might be a good place to start and seeing if that is able to carry the signal across the material. Observing the COMPIN signal at your point of interest will be the best indicator of how the signal is traveling through the tank. If the signal is really weak or you are not getting anything try reducing the thickness.

Best,

Isaac

Hi Isaac,

Good news, sorry for the late update. pls see the below picture

currently i am only able to measure around 30mm-50mm of the water level due to the size limitation of the tank.

another question, if let say i wanna connect this eval board to the other MCU, send this TOF/TDC to the other MCU, what is the best recommendation?

or we should only connect start and stop to the GPIO will do?

thanks,

Chin

Hi Isaac,

May i know whether the eval board can be auto run? i mean without the need to connect to the GUI,

thanks,

Chin