ok,
Water level/height above the transducer.
How is the transducer fixed to the base of the container.?

I am using ultrasound gel as a coupler between the metal surface and the transducer and the transducer sticks to the base of the container.
Yes, you can visit the link below to see the details of the transformer:
https://in.element14.com/prowave/k4...4_India/c/transformers/specialty-transformers

 

hi,
Those transformer are in the 40kHz to 125kHz range.
If you check your ringing image frequency its approx 45kHz!!!
I will run a simulation and post the results.
E

 

hi,
Those transformer are in the 40kHz to 125kHz range.
If you check your ringing image frequency its approx 45kHz!!!
I will run a simulation and post the results.
E

Thanks Eric Gibbs, That would be very helpful.
Yes, these matching transformers are of 40kHz to 125kHz range, because there are no 1 MHz transformer available in market, still I am getting some echo's, I don't know exactly what are these wobbling response when I connect piezo to the container. See the attached image.

 

The circuit works fine on plastic bottles and steel bottles, but the I am not able to get any echo on steel container.
Can someone suggest few ideas that I can use to make it work on steel containers????????

It is usual situation, because of ultrasonic wave attenuation due to metals grain structure.
For example: https://www.jstage.jst.go.jp/article/matertrans/advpub/0/advpub_M2016199/_pdf

 

hi.
Look at this ferrite core PDF, wind your own transformer.
I used to wind my own transformers for 30kHz , 150kHz, 200kHz transducers.

Those wobbly response could be vibrations of the container or electrical noise.

E

 

hi.
Look at this ferrite core PDF, wind your own transformer.
I used to wind my own transformers for 30kHz , 150kHz, 200kHz transducers.

Those wobbly response could be vibrations of the container or electrical noise.

E

Hi EricGibbs,
Thanks for the PDF guide to design transformer.
I was wondering if there is another way to drive the ultrasonic transducer, i.e, without using transformer (as circuit schematic posted before) by using some arrangement of LC tank circuit???
What is it that the transformer does, which we are not able to achieve with LC tank circuit?
Please let me know your suggestions...

 

Hi Tonyr,
Thanks for your reply.
I am trying to measure the fluid inside the steel container, as you said that the first echo is reflected from inner surface of the wall and second from the surface of fluid, but i am not able to see first or second echo too, I also reduced my sweep upto the point..but still nothing. Are you suggesting that there might be some imperfection in the container that restricts the echo from coming back or so?

No, I'm not suggesting that an imperfection would block the signal. However, keep in mind that the sound wave has a specific amount of energy in it. A defect will have a shadowing effect where a small portion of the signal will be lost (reflected back by the imperfection). Even still, there should be sufficient amplitude to the sound wave to reflect off of the inner steel wall. Keep in mind that regardless of the fluid level, you will see that reflection. If the tank is too large your signal can be lost or can take an extreme amount of time to reflect back. Your test targets sound like they were relatively small. When people describe their experiments I try to imagine in my mind exactly what they're doing. I develop a picture that is often not accurate. Your test targets may have been a diameter of 3 inches (7.6 cm). A sound wave will reflect back from that fairly easily. Also I'd expect that the small container would have a wall thickness measured in 16ths of an inch. Maybe 1/16 or even 3/32 inch, whereas the container you pictured (looks like a stainless steel beer keg) might be thicker, say 3/16 or even a little thicker. In terms of sound waves that's a pretty big difference.

With the test target, the sound wave passes through the wall, travels through the fluid, strikes the far wall of the container and bounces back. That would be an indicator of a liquid being present. If the container - at the point of measurement - is empty (no fluid at that level) the sound wave will not pass through and bounce off the far wall. The LIVE target (your tank) the sound wave has to travel all the way across the inner diameter and bounce off the far wall. If that live target is 2 feet in diameter then the sound wave has to travel 4 feet (2 feet there, reflect, 2 feet back) before the transducer will pick up the echo. That will be an extremely long time for a return signal to come back.

Other factors that may inhibit your measurement can be turbulence in the tank (noise as far as sound waves are concerned). You can lose your incident wave in the noise. And yet another possible cause for error can be the viscosity of the fluid being measured. Sound travels at different speeds through different medium. Density has a lot to do with sound propagation.

To be honest, I don't know if it will be doable. The tank is large enough for you to measure the weight. If you can determine the container (tare) weight you might be able to weigh the container and determine how much fluid is in it. But that would require you to know the specific weight of that fluid. There again different fluids have different weights. That's why oil floats on water, water is denser. Salinity also affects the weight of water. Salt water is lighter than fresh water. That's the reason for the oceanic conveyor belt that flows fresh water deep to the bottom of the ocean, flows along the floor until it mixes sufficiently with salt water and finds a return current back to where it started from. A bit off topic, but the point is that measuring fluid level has always been difficult. I personally don't know of anyone who has done it easily. By now I'd imagine someone has figured out an easy way to determine that. In fact, it sounds like your approach may merit further research. It's just that I don't know if you're going to be able to successfully measure a tank of that diameter.

 

If you observe closely, then the ringing is about 500 uSecs.
I am trying to determine the water level below the ultrasonic beam i.e, as the transducer is placed at the bottom of the container, the ultrasound travels through water and gets reflected back from the top surface of the water.

OK, this changes things for what I was imagining. For some reason I was fixated on the idea of putting the transducer on the side and trying to detect whether there was fluid beyond the wall or not. Now I have a better idea of what you're trying to do - to measure the depth from the bottom of the tank. That changes things a little.

In my experiments with ultrasonic waves propagating through water, there are (struggling to think of the correct terminology to describe this) I guess "Focal" points where the waves are strongest and where they are weakest. Using an ultrasonic jewelry cleaner I used to clean inspectors stamps. Simply putting them in the water didn't do much. But if you held the stamp over the center of the transducer and at the right depth you'd get a locally intense energy zone where the stamp would appear to explode and the gunk that built up on the stamp would be dislodged and the stamp cleaned. Just for kicks I put my finger in the water. It wasn't until I hit that exact point that I felt the intense pressure of the sound waves. And it hurt! But above or below that point there was no pressure detected. Not by hand anyway.

With the sound wave propagating that long a distance it might be possible that the secondary (returning) waves can be canceling out the primary waves and you can be losing your energy that way. I don't know if this may be a solution to the problem but maybe your waves are too short. Perhaps a sweeping signal sweeping through a series of wavelengths might serve better. Perhaps at a particular depth (height of fluid) a standing sound wave at a specific frequency will resonate. Off hand I don't know the wave lengths, I'm sure they can be gotten from some engineering book, but, and I'm going to make up some numbers for this, if a frequency of 100 Hz has a wavelength of 24 inches then a frequency beamed into the bottom of the tank at that specific wavelength will resonate as the returning wave bounces back and meets a newly propagating wave. The resonance will indicate that you've found the depth. I'm just thinking ultrasonic waves may be too short to measure that kind of depth. Again, I don't KNOW this to be true, but I think it may be a reasonable approach, worth considering.

 

hi h.y
This simple TX/RX circuit is one option, use the Ardunio program to provide Suppression for the ringing at the TX time.

For determining tidal water height I used 150kHz transducers, located above the water surface, looking down at the surface.
The 150kHz transducer are the low cost type used on sailing yachts.
Drive them with about 20W to 30Watts depending upon the water height range.

Is your transducer the submersible type with a sealed water gland for the cable.?

E

 

OK, this changes things for what I was imagining. For some reason I was fixated on the idea of putting the transducer on the side and trying to detect whether there was fluid beyond the wall or not. Now I have a better idea of what you're trying to do - to measure the depth from the bottom of the tank. That changes things a little.

In my experiments with ultrasonic waves propagating through water, there are (struggling to think of the correct terminology to describe this) I guess "Focal" points where the waves are strongest and where they are weakest. Using an ultrasonic jewelry cleaner I used to clean inspectors stamps. Simply putting them in the water didn't do much. But if you held the stamp over the center of the transducer and at the right depth you'd get a locally intense energy zone where the stamp would appear to explode and the gunk that built up on the stamp would be dislodged and the stamp cleaned. Just for kicks I put my finger in the water. It wasn't until I hit that exact point that I felt the intense pressure of the sound waves. And it hurt! But above or below that point there was no pressure detected. Not by hand anyway.

With the sound wave propagating that long a distance it might be possible that the secondary (returning) waves can be canceling out the primary waves and you can be losing your energy that way. I don't know if this may be a solution to the problem but maybe your waves are too short. Perhaps a sweeping signal sweeping through a series of wavelengths might serve better. Perhaps at a particular depth (height of fluid) a standing sound wave at a specific frequency will resonate. Off hand I don't know the wave lengths, I'm sure they can be gotten from some engineering book, but, and I'm going to make up some numbers for this, if a frequency of 100 Hz has a wavelength of 24 inches then a frequency beamed into the bottom of the tank at that specific wavelength will resonate as the returning wave bounces back and meets a newly propagating wave. The resonance will indicate that you've found the depth. I'm just thinking ultrasonic waves may be too short to measure that kind of depth. Again, I don't KNOW this to be true, but I think it may be a reasonable approach, worth considering.

Yes, I am measuring the fluid level by placing the transducer at the bottom of the container. You might be right that, by changing wavelengths I might get something, but frequency below 400 KHz is consider as Air/Gas transducers, that work in air medium, above those frequencies, I have tried 1 Mhz and 2 Mhz frequencies both of which are giving no significant results.

 

This chart shows wavelengths and frequencies. For instance a 440 Hz wave stands at 30.69 inches. If the tank you're measuring is approximately 32 inches, at 440 Hz the tank will resonate. At resonance you'll know your water level is 30.69 inches. When I talk about using a lower frequency I mean substantially lower than ultrasonic. 1 MHz is not in the sonic range.

As I imagine this testing method - I would suppose it can get quite loud. An operator doing this test may want to do it in a sound insulated room and the operator wearing hearing protection. However, even ultrasonic sound at high enough levels, though not heard, can cause damage to human hearing.

 

hi h.y
This simple TX/RX circuit is one option, use the Ardunio program to provide Suppression for the ringing at the TX time.

For determining tidal water height I used 150kHz transducers, located above the water surface, looking down at the surface.
The 150kHz transducer are the low cost type used on sailing yachts.
Drive them with about 20W to 30Watts depending upon the water height range.

Is your transducer the submersible type with a sealed water gland for the cable.?

E

Hi EricGibbs,
Thanks again for your efforts, I really appreciate your guidance.
I have ceramic disc piezo transducer, which is not submersible (Whose Chinese datasheet I shared with you earlier) & Also I have a submersible piezo transducer both of frequencies 1 MHz.
The thing is that, the containers are sealed, and I have to place the transducer on the surface of container such that, I am able to measure the fluid level inside the sealed container.
Also, can you suggest the circuit without transformer (by using LC tank oscillator).
I am sharing another datasheet of 1 MHz Transducer I have. Please Find Attachment and refer to DM1000 sensor.

 

If the containers are sealed then you should be able to ascertain the fluid level based on weight. NO? Would not the KISS principal apply here?

 

If the containers are sealed then you should be able to ascertain the fluid level based on weight. NO? Would not the KISS principal apply here?

Hi Tonyr,
The reason I cannot use load cell to measure level is because these devices will be mounted on the container at all times, and if the containers are stored in storage, one on the other, then the weight sensor will have to be calibrated accordingly, which will not be feasible.

 

Hi EricGibbs,

The receiver part works fine, but I am still not able to reduce ringing time of transformer. I am planning to replace the transformer with LC tank oscillator which will reduce ringing time. Do you have any suggestions about the LC oscillator....

 

hi h.y.
I would wind a small ferrite core based transformer, there are types with a centred tuning 'slug' [screw] , so that you can trim the frequency.
In practical echo sounders I have found it necessary to add swept Timed Gain Control to the receiver.
At the TX instant the Gain of the amp is low and then the gain increases with time.
Also you will require a echo Suppression during the TX period and extending for few uSecs after, this can be done hardware or the program,

E

 

hi h.y.
I would wind a small ferrite core based transformer, there are types with a centred tuning 'slug' [screw] , so that you can trim the frequency.
In practical echo sounders I have found it necessary to add swept Timed Gain Control to the receiver.
At the TX instant the Gain of the amp is low and then the gain increases with time.
Also you will require a echo Suppression during the TX period and extending for few uSecs after, this can be done hardware or the program,

E

Hi Ericgibbs,
How do you suggest echo suppression to be done using hardware, I have been trying to use a MOSFET as bridging switch which will turn OFF during the TX period and turns ON during Echo Listening period, But I haven't been able to get any good results with it.
It would take time for me to wind up the transformer as I will have to do calculations and stuff and I am already running behind, so I was looking for something with LC oscillators that would boost the voltage to the transducer.
B.T.W, how is it that I am not able to read any amount of current through the transducer through my multi-meter, is there something I missed or Is there some other way to measure current going into piezo?...

 

hi,
The current cannot be measured by using a DVM, its pulses are too fast and the burst is only 10uSec.
I have just simulated that circuit so that you can see the current waveform. I(R5)

I would recommend that you consider downloading the free LTSpice simulator, I could then post my circuits for you to run.

E

 

hi,
The current cannot be measured by using a DVM, its pulses are too fast and the burst is only 10uSec.
I have just simulated that circuit so that you can see the current waveform. I(R5)

I would recommend that you consider downloading the free LTSpice simulator, I could then post my circuits for you to run.

E

View attachment 172285

Hi,
Okay, I have downloaded the Free LT-spice simulating software.
Please share a circuit for TX part of transducer, without use of transformer, it would be helpful and easy for me to assemble the components on breadboard for live testing as well.
The major components that I have in-hand right now are:
1. 2n7000
2. 10uH inductor
3. Resistor of different values

 

hi,
Attached the LTS 'asc' file, just click and run.
E