just some useless information....
the waterproof comes from an aluminim can.
the sensor is a piezoelectic disk that is in contact wth the aluminum, then using a lot of cork to eleminate backwards reflection or just filler, and a lot of some sort of filler, (assuming silicone) the can is filled so water cannot get in.
the best I can figure is the piezo element is energized and sends out it's pulses
the aluminum is then vibrated like a bell
the aluminum transfers that to the medium
the sensor is de-energized and sufficent time for the aluminum to stop rining is allowed to prevent false readings.
the pulses reflect back from the object of interest.
the aluminum rings again and that is transferred to the piezo sensor that is then sensing the vibration.
the best I can figure is that the initial vibration, aluminum ringing, etc, has to have a dead period to allow the device to go from source to sensor. this dead-band causes the device to have a minimum distance of use in air.
the use of this in a fluid is great that you thought of it and that you were able to get it to work at all.
the fact that you chose a meter was a great help in your getting anything to work at all.
I tried using the vegetable oil now, and I'm not getting any readings when I put the sensor in the liquid. The vegetable oil is the 3rd thickest liquid I am using. If I cant get a reading in vegetable oil, I won't be able to get a reading in molasses. Does anyone know if there is a way to boost the signal strength of the ping?
Dave-in-nj. My teacher said everything had to be done using metric system, and since speed can be measured in meters/sec, I just figured it would make my calculations a lot easier if I had 1 meter tubes. I just didn't think I would have so much trouble getting consistent ping results or any results at all now
IrishGunnners29:
I tried using the vegetable oil now, and I'm not getting any readings when I put the sensor in the liquid. The vegetable oil is the 3rd thickest liquid I am using. If I cant get a reading in vegetable oil, I won't be able to get a reading in molasses. Does anyone know if there is a way to boost the signal strength of the ping?
Then you need a much shorter tube! Just extrapolate the readings for a 1 meter tube.
Paul
Have you made sure that the sensor works in air, and that you can use it to measure, for example, air temperature over a fixed path length?
IrishGunnners29:
I tried using the vegetable oil now, and I'm not getting any readings when I put the sensor in the liquid. The vegetable oil is the 3rd thickest liquid I am using. If I cant get a reading in vegetable oil, I won't be able to get a reading in molasses. Does anyone know if there is a way to boost the signal strength of the ping?
have you tried to use incrementally more viscous fluids ?
Is the time getting longer or shorter as the water chills ?
This is Brennen's father. I want to thank you all for giving your suggestions to my son. He may have been a little too ambitious for this project, but you live and learn. I am trying my best to help him with this project, but I am running out of suggestions. I cut one of his tubes down to a 1/2 meter for both the cooking oil & molasses.We still can't get a reading from the molasses, and the cooking oil is just not right. Having cut the distance in half, he should be getting a reading much closer to 1/2 of what he is getting for the liquids in the 1 meter tubes. Tap Water 1254us, Isopropyl Alcohol 1270us, Distilled Vinegar 1285us. The cooking oil is giving a reading of 1227us in the half meter tube. I had him try max distance at 100cm and 50 cm, and the results are the same. Additionally, I anticipated the rubbing alcohol to be less dense than the distilled vinegar resulting in a slower response. What are we doing wrong? Any suggestions are greatly appreciated.
IrishGunnners29:
I tried using the vegetable oil now, and I'm not getting any readings when I put the sensor in the liquid. The vegetable oil is the 3rd thickest liquid I am using. If I cant get a reading in vegetable oil, I won't be able to get a reading in molasses. Does anyone know if there is a way to boost the signal strength of the ping?
The subject line should read viscosity not velocity
If you are getting readings in warm water.
Does the time increase or decrease in chilled water.
Ie viscosity change.
Last time i checked half a meter was still metric
Imho, valid results could be
500ms results
.5674 meter warm water
.5129 cold water
.439 salt water
.343 meter molassas
All calculations with 1 constant and 1 variable will work. If one constant is causing problems, adapt and overcome.
Document how and why
What are we doing wrong?
You are assuming that a transducer and circuit designed to work in air will work in liquids. Generally, that is not the case. The transducers designed for water are completely different in design, and have to be, for technical reasons (the acoustic impedance of water is about 3600 times higher than that of air).
Basically, a transducer designed for air is extremely inefficient at coupling sound energy to liquids, so both transmitting and receiving are drastically affected.
Then, there is the circuit, which sends out a short burst of pulses. It has to wait for the transducer to stop "ringing" before it can receive a reflection, which is on the order of a millisecond. Even if your transducer worked in liquid, if a reflection were to arrive before that, it would be ignored.
This topic appears to be dead in the water 
, but for future viewers...
IrishGunnners29:
...I cut one of his tubes down to a 1/2 meter...
This sensor has a dead zone of 20 cm in air (can't read distances closer than that, due to the ringing previously mentioned).
Since the speed of sound in water (and cooking oil) is about 4.4 times faster than in air, there's probably a dead zone of about 90 cm for those liquids.
That is, you should use a tube at least 90 cm long, preferably longer, assuming the sensor is capable of functioning in the liquid.
Also, since you're apparently getting approximately the same time of flight regardless of tube length, none of the results seem to be valid.