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[on:]

If I keep the ultrasonic sensors (40KHZ/25KHZ) in a sealed plastic container, will they still measure the distance? I want to measure the water level in a tank about 10ft depth and I don’t have the water proof ultrasonic sensors available at my place. Any suggestions are welcome.

[Reply #1 on:]

I think that will block the ultrasonic sound.

[Reply #2 on:]

Yes, won't work. You might look into analog IR sensors, they might work through a transparent cover. Sharp makes some but you have to watch that the minimum and maximum ranges match your application.

Lefty

[Reply #3 on:]

If I keep the ultrasonic sensors (40KHZ/25KHZ) in a sealed plastic container, will they still measure the distance? I want to measure the water level in a tank about 10ft depth and I don’t have the water proof ultrasonic sensors available at my place. Any suggestions are welcome.

I don't know your exact usage, but maybe instead of measuring the depth of the water from the surface down, you could measure the distance from above the surface to the water's surface.  Then, with a known surface level and depth, you could easily calculate the depth.

In other words, put the ultrasonic sensor let's say 1 foot above the surface of the water.  The sensor would measure the distance as 12 inches.  You then measure the distance from the sensor to the bottom of the tank, lets say it's 132 inches.  So, when the sensor reads 12 inches, you would do 132-12=120 inch water depth.  When the sensor reads 15 inches, 132-15=117 inch water depth.

While the ultrasonic sensor won't work under water, the ping will reflect off the water's surface.  Not knowing your exact usage maybe this won't work.  But, if it's a tank, it has a static depth and probably a place to mount the sensor above water.  If you do choose to use an ultrasonic sensor, may I suggest the NewPing library which has a ping_median method that would work nicely to filter out noise and get an accurate measurement with something like this that's probably not moving quickly.

Tim

[Reply #4 on:]

Thanks All for your responses!

@Tim, Thanks for your suggestion!.  Its a closed underground tank and I can mount the sensors above the water surface without any difficulty. But there will be lot of moisture inside the tank and I read some where that the moisture inside the tank can damage the sensors.Not sure if its true, that's why I was looking for the water proof sensors, but unfortunately those are not available here. 

[Reply #5 on:]

.Not sure if its true, that's why I was looking for the water proof sensors, but unfortunately those are not available here.

what about automotive sensors?

[Reply #6 on:]

Hello from France,


Even if you find an ultrasonic sensor to put in the water, the speed of sound if a lot more high in water than in air, so it could be difficult to work with.

May be you can use a pressure sensor. You just have to put it at the bottom and read the pressure : about  14.5 PSI for 33 feets of water depth.

[Reply #7 on:]

.Not sure if its true, that's why I was looking for the water proof sensors, but unfortunately those are not available here.

what about automotive sensors?

From one of my sensorics classes:
Automotive sensors (older versions, and maybe even some new ones), are essentially created from the floating part and the resistor wire...
The floating part is sliding on the resistor wire, giving us the exact volume of the liquid inside the tank (like a pot meter)...
Older car models had a 12V system, so if you hit something, and +12 and GND shorted, well the car would blew up...
My teacher had the opportunity to open one of cars tank, and he found out that the wires, and the connectors of the sensor were so badly insulated, and that every petrol car is essentially a time bomb (imagine riding over bumpy roads)...

So if your liquid won't blow up, you could use the existing car sensors.

[Reply #8 on:]

No, I meant automotive ultrasonic parking sensors.
It seems to me they'd have to be at least a little moisture resistant.

[Reply #9 on:]

No, I meant automotive ultrasonic parking sensors.
It seems to me they'd have to be at least a little moisture resistant.

there are 2 types of commercial parking sensors:
ultrasonic sensors --> made from "speakers" and they have no big protection (because any significant protection would block the sound)
and
IR sensors (IR diode, and IR reciever) can be behind a glass or plastic --> and that thin plastic layer makes them "moisture resistant"...
but, if the moisture blurs the thin plastic layer, the sensor will stop working, and you will have to wipe the thin plastic in order to get it working again

[Reply #10 on:]

My car has both front and rear ultrasonic sensors.
I would have thought that they'd be at least IP65 to withstand rain hitting them at over 160 kph.

[Reply #11 on:]

My car has both front and rear ultrasonic sensors.
I would have thought that they'd be at least IP65 to withstand rain hitting them at over 160 kph.

Fair enough, here is the topic about "preserving" ultrasonic sensors (so it is possible).
http://forums.parallax.com/showthread.php?94365-Using-the-Parallax-Ultrasonic-Sensor-to-measure-liquids-%28Need-to-add-protectio

[Reply #12 on:]

My car has both front and rear ultrasonic sensors.
I would have thought that they'd be at least IP65 to withstand rain hitting them at over 160 kph.

The issue is not if a sensor that can withstand rain (obviously, they can as weatherproof ultrasonic sensors exist).  The issue is will it actually work while submerged.  Put your car under water, back up, and see if the sensors works.  I would guess they won't.  The ability for the sensor to withstand rain at 160kph is meaningless in this context.  Will it work underwater is the question, and your car sensors I'm sure wouldn't.  But, I would suggest trying, just to be sure ;-)

Tim

[Reply #13 on:]

How can you acces the tank?

You can measure
-the weight of the tank
-measure the distance from the top untill water/fluid comes (watersensor with steppermotor).
-as posted before the pressure at the bottom with good knowledge of the tanks properties

you could add led+lightsensors in certain distances at the inner walls...

=====
about the waterresistant ultrasonic sensors.

In generall the speed in water is ~4times higher than in air. As far as i know also your range will decrease drastically but i guess with the right sensors/amplifier thats not a problem.
But we wont measure under water? Im not sure if mounted at the bottom these will measure the top of the water as it doesnt reflect. And a swimmer to measure the bottom distance isnt the easiest too.

=> but for cars there are sensors that work in air and are water resistant.
http://futurlec.com/Ultrasonic_Sensors.shtml

"Waterproof Ultrasonic Sensor II
Waterproof Ultrasonic Sensor for use outdoor and in high-humidity areas. Excellent for alarm systems"

http://arduino.cc/forum/index.php?topic=94244.0

[Reply #14 on:]

Will it work underwater is the question, and your car sensors I'm sure wouldn't.

I thought we'd moved away from that, and were measuring the void above the liquid surface, where the worst we could expect would be vapour or condensation.