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Ultrasonic trans/rec transducer support hardware

Delta Prime

Jul 29, 2020
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What is a 10-turn preset?
A potentiometer, commonly referred to as a “pot”, "trimmer","preset" is a three-terminal mechanically operated rotary analogue device which can be found and used in a large variety of electrical and electronic circuits. ;)
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HANKMARS

Jul 28, 2019
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10 precicion pot 1.1.pngThe thot of trimmer pots went thru my head but I visualized the single turn 1M ohm ones that I use on another project and I ruled out trimmer pots. I resigned myself to having to use precision 10 turn pots with locking knobs, usually around 10 bucks each. Thanks for jogging my memory. I think the 10-turn PCB mount pots will still be a little "springy" but also think that they will stay set more so than the larger panel mount pots. Especially if I drop a little locktite or maybe nail polish on adjustment screw. This is the first time I heard these pots referred to as presets. But then again, it was just last year I first heard the term valve in reference to what I had for years called vacuum tubes.
 

kellys_eye

Jun 25, 2010
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Shame you aren't UK-based. I could chuck a few items like those your way as I have a selection in my 'crap' box.....
 

HANKMARS

Jul 28, 2019
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Shame you aren't UK-based. I could chuck a few items like those your way as I have a selection in my 'crap' box.....
The sentiment is much appreciated but I will order an assortment of "presets" for my own goodies box. The overall value I need in that particular leg of the circuitry is ~134k ohm. As it sits, I'm using a 68k fixed resistor and a 100k single turn panel mount pot. Because thats what I have on hand. If I change fixed resistor to ~ 130k then use a 10k pot, the springyness will be a lesser concern.
 

batdetector

Jun 4, 2023
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Hi Hankmars. Your transducers will need to be a contact type rather than air interface. However, you are going to have problems with getting the sound through the tank wall and resonances from the tank material itself.

It might be better to try a completely different approach: if the tank is plastic, how about sensing capacitance between a pair of metal plates? It will be higher where the liquid is.

Or even simpler, a pair of PIR sensors: the liquid is almost certainly going to be at a different temperature.

Just noticed the date of the thread. Doh.
 
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HANKMARS

Jul 28, 2019
498
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Hi Hankmars. Your transducers will need to be a contact type rather than air interface. However, you are going to have problems with getting the sound through the tank wall and resonances from the tank material itself.

It might be better to try a completely different approach: if the tank is plastic, how about sensing capacitance between a pair of metal plates? It will be higher where the liquid is.

Or even simpler, a pair of PIR sensors: the liquid is almost certainly going to be at a different temperature.

Just noticed the date of the thread. Doh.
My projects tend to stretch the projected time tables. My initial thot was capacitive difference as the indicator of liquid level. I did an experiment but results showed only a difference of a few pico farads. I did not feel secure with determining such a small value accurately and repeatable. This is now a simple level indicator. I have enough circuitry to start testing on units similar to actual tanks. I think I will be able to make a convincing argument as far as corrupting tank integrity with 2-3/4 inch holes in it's top. I did some calcs a little while back regarding travel speed of the sonic burst. I recall a time period of 0.9 ms to 1.0 ms per 12 inches of travel. Sound about right?
 

HANKMARS

Jul 28, 2019
498
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Messages
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Hi Hankmars. Your transducers will need to be a contact type rather than air interface. However, you are going to have problems with getting the sound through the tank wall and resonances from the tank material itself.

It might be better to try a completely different approach: if the tank is plastic, how about sensing capacitance between a pair of metal plates? It will be higher where the liquid is.

Or even simpler, a pair of PIR sensors: the liquid is almost certainly going to be at a different temperature.

Just noticed the date of the thread. Doh.
PIR? Infrared? Is suspect I would need to scan entire height of tank.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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I have been following this thread with some interest... years ago we did a lot of outdoor cooking on a propane gas-fired grill. The propane tanks were heavy when filled and a lot lighter when empty. The difference between "filled" weight and "empty" weight is easily measured with a bathroom scale. Problem is, I didn't want to unhook the tank from the grill in order to weigh it, but I didn't want to run out of gas while cooking either.

So, I found a plastic tape with a sticky backing that is coated on the top side with liquid-crystals that change color with temperature. The tape is placed vertically on the tank, running from near the top of the tank to near the bottom. You pour boiling water over the outside and then look for a color-change along the length of the strip of tape. Liquid propane absorbs heat differently than the gaseous propane above the liquid. This is easily seen as a change in the color (temperature) of the tape at the demarcation between gas and liquid. Voila! Leave the scale in the bathroom and boil some water to see if the propane tank is empty.

I bought the tape and we used it for awhile. It did work, but having to boil water and pour it over the tape was an inconvenience. Plus, the tape didn't "wear well" when exposed to the outdoors environment. My "final solution" was to purchase a second propane tank, keep it always filled, then swap the second tank for the first one when the first tank became empty. That wasn't ideal either, because refilling a propane tank means you have to find a propane service that will do that. Here in Florida, the nearest propane refill station is several miles away from where I live. Also, refillable propane tanks have to be inspected and certified periodically to be eligible for refilling. So, most of the time, I just exchange the empty tank for a prefilled used tank. That's usually a rip-off compared to refilling your own tank, but most gas stations with convenience stores also sell prefilled propane tanks in exchange for your empty tank. And while you are there, they also usually sell frozen water at rip-off prices.

A few years ago our gas grill rusted out and we had to trash it. I still have the two propane tanks, but we didn't replace the grill. It turns out that amongst the heat, humidity, and flying, biting insects evening outdoor cooking in southwestern central Florida loses its attraction. We still enjoy barbecued chicken and baby back spare ribs, but just a few miles away is restaurant that sells both, for eat-in or take-out, so we do that.

More years ago than I like to remember, I had to make a trip to Dallas, TX, to examine an infrared television camera system made by Texas Instruments. A customer wanted to install it on coastal patrol boats and use it for surreptitious observation and weapons aiming at suspected smugglers. Although this system was to be exported to one our allies in Europe to be used for the interdiction of smugglers, my only job was to make sure it was actually up to performing the task.

So I got to see a fancy "dog and pony show" at TI. They had their camera system set up in an elevated laboratory with open windows overlooking an interstate highway several miles away. The camera would normally be attached to a set of azimuth and elevation gimbals that were under the control of the image processing software. The operator simply identified a target with a video cursor and the system would then track that target on-screen or by either moving the camera in azimuth and elevation to keep the infrared image on-screen, or by moving the cursor if the target remained in the field-of-view of the camera.

Presumably, installed on a boat, the camera gimbals and tracking cursor would also be "slaved" to a gun mount, with a computer in between to calculate the lead angle and elevation angle necessary to place rounds on the target. Of course in Texas we didn't have a gun or cannon or missile launcher or whatever the customer intended to use, but I could manually hold the camera, select a target, and then observe that the target was "tracked" on-screen as I moved the camera around in the field of view. Totally subjective evaluation, but I was impressed at how well it worked tracking vehicles on the highway. While I was there, I pointed the camera at a tall storage tank near the highway. Whatever was inside that tank heated up nicely in the Texas mid-day sun. The demarcation line between liquid in the tank and gas above the liquid was easy to see. So, for this solution to "how much liquid is in the tank?" all you need is a few hundred thousand dollars, if you are military or a foreign government, or a few thousand dollars if not. This technology is now available to the public.

Every time I pass by a water tower, or any large storage tank, I ask myself, "I wonder how full that is?" And then I ask myself, "How would anyone find out?" After some research, I discovered the simple answer: weigh the tank! So we are back to my propane tank for my barbecue... It turns out that "weighing the tank" is used not just for liquid but also for solids, like grain. It does require some planning and forethought before building and filling the tank, but with load cells it is remarkably easy and reliable to measure the weight of almost anything.

Which brings us around to ultrasonics and other methods. Ultrasonic, as well as radio-wave, transmitters and receivers have been used for many years to measure the volume contents of storage containers. X-rays, or other emitters of penetrating ionizing radiation, are also used as probes, mainly for pipe lines to detect weld defects, not the contents of the pipe. Anything that will pass through tank walls, and be differently affected by the presence of liquid versus gas, will work. Back in the day, a long, hollow, vertical glass cylinder, with the ends bent over at ninety degrees and piercing the tank wall, was used to actually see how much liquid was present. This high-tech gadget, called a "sight glass," was easy to use in conjunction with the Mark I Eyeball.

There are all sorts of other methods used to determine the quantity of substance in a tank, but all (or most of them) require an invasive system, such as a float, to operate. That seems to be a non-starter for your application.

Since you have been somewhat evasive on the actual application, I can only offer ideas. I think that a handheld imaging infrared camera is probably what you need. These used to be very expensive to build because the infrared sensors needed liquid nitrogen cooling to get the infrared signal above the noise floor of the sensor. Today, imaging micro-bolometers (thousands of thermocouples in an x-y array) are available that operate at ambient temperature.

The cost of the one that is linked-to above is currently less than 700 bux. If you can get that down to, say, 70 or so... it should sell like hot cakes. That would require some serious engineering and it probably would not be as quantitatively accurate. It should be adequate for determining liquid level in most tanks, because that application just requires a go/no-go decision on where the level is. It is not necessary to determine what the liquid temperature is, only that the temperature of the liquid phase is sufficiently different from the temperature of the gas phase to be visibly contrasting.
 
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