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Ultrasonic trans/rec transducer support hardware

HANKMARS

Jul 28, 2019
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I will be using an ultrasonic transducer (t/r). Ideal signal is 40 kHz. 10 V nominal to transmitter. I am assuming I need to supply a 10 Vpp 40 kHz signal (squarewave?) to transmitter. Also I'm guessing a 40 kHz pass filter will be needed on the receiver component. What I am trying to determine is when a gaseous volume is replaced with a liquid volume, from outside of the holding tank. My notion is to transmit a short burst of signal then measure the time period of the reflected signal. With such a difference in density between the gas and the liquid, I believe the echo times will be easily distinguished. Not certain but my best guess. Where can I find some detailed information for a setup like this?
 

kellys_eye

Jun 25, 2010
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There are formulae for the speed of sound in liquids/solids/gases and, I wouldn't doubt, probably some on-line calculator too if you searched with the right words!

The principles you describe are perfectly sound (no pun intended) but what is the actual application?
 

HANKMARS

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There are formulae for the speed of sound in liquids/solids/gases and, I wouldn't doubt, probably some on-line calculator too if you searched with the right words!

The principles you describe are perfectly sound (no pun intended) but what is the actual application?
I am reluctant to tell you the actual application. It is a simple application. My friend and I feel as though the device that I am working to design is a viable product and may be easy to market. If retail price can be kept at a level whereas even the impoverished can afford to purchase the device, I would expect that fabrication by an individual or small team could be steady for at least a year just to meet local sales demand. With only me as the design, fabrication, marketing and technical support departments, development is considerably slower than an established product development company. My current timeline says I'll have a functioning prototype ready by April, a production model finalized by May. At that time, I can start gathering "intent to purchase" affidavits. I will present the affidavits along with a 5-year business plan to potential investors. I am talking about locals as investors. Friends and acquaintances they may want to help fabricate or sell the product for a percentage of profits. 20 years ago, when I researched available investment groups that would provide seed money, not many were interested in business concerns asking for less than 500,000 dollars. It's a little late in the day for me to be looking 30 years down range.
 

HANKMARS

Jul 28, 2019
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I did find some videos dealing with ultrasonic transducers. Most were either involved with piezo type transducers, which mine are not, or the video was about ultrasonic cleaners.
 

HANKMARS

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I did acquire some experience working with ultrasonic transducers when I worked for a man that developed a device called Preg-Check. I'm from Iowa. Pigs are big business there. Some hog farmers may have several hundred brood sows. Large groups of these sows would be bred at the same time. It was beneficial to determine if a sow was successfully impregnated. If they failed to become pregnant, that was a non-productive animal that still needed food. If, after breeding, within a few days you could proclaim a sow not pregnant, she could be bred again and would farrow with the same group. Hence, Preg-Check. A hand-held device a little larger than a pack of cigarettes. The bred sows were run thru a shoot where they could be stopped and held while the technician would lift a hind leg slightly, press the transducer on the top of the Preg-Check unit against the inside of the flank. The tech would depress a momentary button switch on the unit and one of 2 LEDs would illuminate. Red indicated that the sow was not pregnant, yellow indicated the sow was pregnant. When a sow becomes pregnant her uterus begins to fill with liquid. The liquid has a different density than does the tissue of which the uterus is made. This difference in density would affect the travel time of the reflected supersonic wave returning to the transducer. The Preg-Check had circuitry that would determine if the time period from initial signal sent until the signal reflection was detected, corresponded to pregnant or not pregnant and illuminated the corresponding LED read out. I'll be doing essentially the same thing. I will be comparing the time period of the reflected wave burst to a known value to determine if a vessel contains gas or liquid.
 

kellys_eye

Jun 25, 2010
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The difference between sound transmission in a gas as opposed to liquid is very marked and should be an easy test/determination. You'd be better off making a circuit and doing the actual comparisons yourself than trying to design around figures someone else produced.
 

HANKMARS

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The difference between sound transmission in a gas as opposed to liquid is very marked and should be an easy test/determination. You'd be better off making a circuit and doing the actual comparisons yourself than trying to design around figures someone else produced.
I agree. I believe I can find time periods of reflected signals through experimentation. My SWAG (scientific wild ass guess) is that the more dense liquid will impede the rate of travel of the sonic burst more so than will the gas. Let's assume that to be true for now. So, if I find a nominal length of time required to detect the reflected sonic pulse when volume is a gaseous state, I will add a small percentage of that value to itself as a fudge factor. After a burst is transmitted the control program will loop around maybe only two questions. Has the reflected pulse been detected? No. Is my timer value greater than my set value? No. Has the pulse been detected? No. Is my counter value greater than the set value? YES! Oh. By default, I have determined that the vessel now contains liquid. The change of the volume from gas to liquid to gas to liquid is an on-going dynamic process so another burst will be fired, and the two-question subroutine will again loop waiting for a yes or no answer to base its determination upon. What I am wondering is if the sonic burst is somehow focused or if it is free to propagate in all directions at will. In the Preg=Check device I think the signal traveled only about 4 or 5 inches ( the approximate distance from inside of the flank to the center of the uterus) but I cannot imagine how that could be accomplished and even if it was focused, why would the signal suddenly bounce backwards?
 
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kellys_eye

Jun 25, 2010
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My SWAG (scientific wild ass guess) is that the more dense liquid will impede the rate of travel of the sonic burst more so than will the gas.
Quite the reverse. The denser the medium the faster sound travel through it.

With a known density medium you test 'continually' for received signal by varying the sampling time. You will sense a received signal as long as the material remains the same (i.e. same transmission time throughout) but, when the sampling time reaches the point at which the transmission medium changes (i.e. from liquid to air) the expected reception time will change i.e. it will either be later - if the transition is from air to liquid - or it will be sooner - if the transition is from liquid to air.

Using air and liquid as the boundary definitions means it's fairly easy to make the test/determination as the state transition is marked - doing it with flesh and liquid will, of course, mean more required accuracy given the transmission time difference will be so much smaller but that shouldn't prove an issue with modern technology.

My understanding is that typical ultrasound devices for pregnancy (human) testing uses this technique and the sensor is an array of ultra sonic transducers in order to deliver a focused beam - that type of application requires yet more careful timing as the individual ultrasonic transducers have to be activated in a particular timed sequence to get the right beam shape.

Maybe research some human-application ultra sonic devices to get a better idea of the theoretical requirements? I'm no expert on the subject and offer the above as layman's opinion/understanding only.
 

Bluejets

Oct 5, 2014
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I will be using an ultrasonic transducer (t/r). Ideal signal is 40 kHz. 10 V nominal to transmitter. I am assuming I need to supply a 10 Vpp 40 kHz signal (squarewave?) to transmitter
Thought about the Arduino HC-SR04..??
All done in a package for a couple of dollars.
Tranceiver, promini, 5v supply and a bit of code (mostly already written a thousand or more times) done.
 

HANKMARS

Jul 28, 2019
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Thought about the Arduino HC-SR04..??
All done in a package for a couple of dollars.
Tranceiver, promini, 5v supply and a bit of code (mostly already written a thousand or more times) done.
I will try to look that up this afternoon.
 

HANKMARS

Jul 28, 2019
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Quite the reverse. The denser the medium the faster sound travel through it.
Thanks for the tip on transmission speeds. I was mixing impedance with wave travel time. Radiowaves in water use extreme wavelengths, I assume because of the viscosity. Maybe more so the mass of water being sluggish in respect to producing a wave. Whereas if you produce a concussion in air, e.g. a speaker cone, the wave will still have a high percentage of initial amplitude at some distance. Travelling at the speed of sound 600-700 mph? Produce that same wave in water, it "travels" more rapidly but amplitude decreases more rapidly. I think. Use a denser medium such as a brittle metal bar, produce the concussion with a hard steel mallet and the detected wave would appear almost simultaneously at 100 yards distance in comparison to an air medium transmission. I'm getting on a tangent here. The opposite wall of the containment vessel will be the reflective surface. The distance of travel will be in feet rather than inches so the difference in time period of transmission to detection will be easily distinguished. The test method for proper calibration, on the Preg-Check device, was a simple matter of pressing the transducer against one end of a custom fabricated acrylic bar. One end of the bar corresponded to flesh and the other end to liquid. Overall length was approx 8". I'll guess the refraction coefficient was a harmonic of the real substance since the acrylic was obviously harder than either of the actual tested substances. The junction of the dissimilar acrylic materials in the test bar acted like a prism and reflected a significant percentage of the sonic signal.
 

HANKMARS

Jul 28, 2019
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Thought about the Arduino HC-SR04..??
All done in a package for a couple of dollars.
Tranceiver, promini, 5v supply and a bit of code (mostly already written a thousand or more times) done.
Where do I shop Arduino?
 

Bluejets

Oct 5, 2014
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Any online supplier...Ebay, Amazon, Aliexpress.....not familiar with Google then ...??
 

kellys_eye

Jun 25, 2010
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The opposite wall of the containment vessel will be the reflective surface.
There are already, on the market, devices for measuring the liquid content of tanks (oil, water, sewage etc) using ultrasonics that may offer a more direct solution to your requirement (guessing). Another place to possibly source transducers and/or electronics.
 

HANKMARS

Jul 28, 2019
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There are already, on the market, devices for measuring the liquid content of tanks (oil, water, sewage etc) using ultrasonics that may offer a more direct solution to your requirement (guessing). Another place to possibly source transducers and/or electronics.
True enough. This particular situation calls for no intrusion inside of the tank. No probes or devices are allowed inside. I do recall seeing an ad for a level indicator that was completely external. I remember the tank was elevated on a stand and I think a transducer was underneath pointed at the bottom of the tank. I will guess that when the sonic signal reaches the upper surface of the liquid where it contacts the air, a reflection is produced. Don't know for sure. I have to assume that the tank wall produces an echo, but I suppose that that echo could be discarded through programming. I am not inventing anything new here, just innovating an existing technology and displaying it in an atypical fashion.
 

HANKMARS

Jul 28, 2019
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All done in a package for a couple of dollars.
Is "a couple of dollars" figurative? Or more like under 100 dollars? I tend to be a tad stingy.
 

HANKMARS

Jul 28, 2019
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Finding buku driver and receiver circuits. These 2 are pretty close to what I had in mind. I will have to add some programmable logic but I'll see how these work. May have to go to ultra-sensitive receiver circuit.TRANSD SET CIRCUITS.1.1.png
 

HANKMARS

Jul 28, 2019
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EP FORUM REPLY 1.1.png The photo in the attachment is of an email I received last night. The best I can tell, the page (419) has expired. Perhaps the message was spam of some sort. Anyway, my transducer transmitter really halls tail when my oscillator hits its resonant freq. I'm using 2 - 555 timers. One produces the 40 kHz trans freq and the other dictates the time period between bursts. I ordered some 8 pin dual op-amps to use on the receiver side. The LM358 I think they were. Seems that 300 kHz was max response but thinking they will work for this app. Getting behind some on timelime due to distractions but still have bread boards right on the bench. A problem I do have is with my fine adjust pot. I can eventually tune in to the transmitter resonant freq but the pot's "spingyness" is a B hatch. Maybe a precision ten turn pot will remedy this. Expensive tho.
 
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